Biog. Mems. Fell. R. Soc. Lond., 46, 125, 2000

NORMAN ADRIAN DE BRUYNE, F.Eng

8 November 1904 – 7 March 1997

Elected F.R.S. 1967

BY ANTHONY J. KINLOCH, FREng.

Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, Exhibition Road, London, SW7 2BX, UK

Norman de Bruyne was a man of outstanding achievements and in 1967 he was elected to

Fellowship of the Royal Society. The citation at the time read:

‘Distinguished for his practical application of science to certain problems in aircraft construction,

especially the use of plastic materials and adhesives…. ’

He was a strong personality and acquired many life-long friends. His approach to engineering

challenges - and a hint of his puckish sense of humour - are contained in the single word that

he used for his entry in ‘Who’s Who’: under the heading ‘Recreations’ he wrote ‘inventing’.

FAMILY BACKGROUND Norman Adrian de Bruyne was born in Punta Arenas, Chile on 8 November 1904. His father had

been registered for a degree in medicine at the University of Groningen and was therefore

destined to follow the same profession as de Bruyne’s paternal grandfather, who was a doctor in

Zierikzee in the Netherlands. However, de Bruyne’s father decided that medicine was not for

him, with the result that he was handed the equivalent of about thirty pounds by his father and

told to leave home. De Bruyne’s father initially worked in France in a tannery, as a tour guide and

as a reporter. He then decided, around 1890, to emigrate to South America where, eventually, he

reached Punta Arenas and the Straits of Magellan. There he opened a store, became the director

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of the Bank of Punta Arenas, the Netherlands Consul, the head of the fire brigade, a sheep farmer

and the director of a whaling company - and greatly prospered. One day he fell off his horse and

was tended by an English girl named Maud Mattock. They were married on 6 August 1895 and

had four boys. (Since they were all born in Punta Arenas in Chile they were, by Chilean law,

Chilean subjects. However, their father ensured that their birth certificates were stamped with the

Netherlands’ consular seal to establish their ‘Dutchness’.)

The eldest boy, Albert Sylvester (1896-1908) died of TB as a child. The second born,

Henry Bernand Arthur (1898-1976) ran the farm in Chile and the next boy, Gordon (1900-1972),

joined the British Army and rose to the rank of Brigadier in the 60th Rifles. The youngest,

Norman Adrian, become a prolific inventor, an engineering entrepreneur and one of the earliest,

and most influential, advocates of synthetic adhesives for use in demanding, and novel,

engineering structures, especially in the construction of aircraft.

SCHOOLING

In 1906 the family moved to Redhill, Surrey, England, although de Bruyne’s father returned to

his farm in Chile for the winter months. However, young Bernand suffered from asthma and in

1910 the family moved from Redhill to Littlehampton, Sussex, England. All three boys went to

day-school at Wellesley House, Littlehampton. De Bruyne was considered a rather slow learner

who found good English Literature, such as ‘Great Expectations’, rather tedious. However, at the

age of twelve his father gave him, at his own request, a two-volume set of a biography of Edison.

These books were far more to de Bruyne’s taste than Dickens, and he later wrote (22) that:

‘They were a revelation and I wandered around in a dream.’

In September 1918, de Bruyne became a boarder at Lancing public school, which was

founded by the Reverend Nathanial Woodard. However, from his very first few hours at Lancing

it was clear that de Bruyne was going to be a misfit.

One reason for this was his dislike and disinterest in most sports. R.F.G. Lea, a fellow

pupil at Lancing who would work closely with de Bruyne in later years, painted the following

picture of de Bruyne’s prowess on the football pitch during a speech to mark de Bruyne’s

retirement from CIBA (ARL) Ltd in 1960 (22):

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‘Without a doubt the most miserable sight I have ever seen in my life was dB as I first remember

him. Clothed in shorts and shirt, he was playing football at Lancing. A cold east wind swept the field, but

while others rushed energetically up and down dB stood for one and half hours absolutely stationary in the

middle of the field, blue with cold, but always politely facing the direction of the ball. He never altered this

way of playing during his career as a footballer.’

De Bruyne was apparently no better at cross-country running, had never learnt to swim and

considered cricket to be boring and a waste of time. However, he did at least partially make his

sporting reputation, and gain his school colours, when he joined the school shooting team which

won the Ashburton Shield at Bisley in 1922. A major factor in his success as a marksman was

that correcting an Officer Training Corps rifle for distance and wind presented a similar

challenge, and degree of difficulty, to him as setting up a reflecting galvanometer!

A second reason for being a misfit was that de Bruyne’s views on religion were a far cry

from those of the founder of Lancing, and from his headmaster, the Reverend H.T. Bowlby. De

Bruyne at first refused to be confirmed, but the headmaster told him that all his prefects were

confirmed and that, if de Bruyne refused, his place at Lancing would be threatened. He took his

dose of what he termed ‘Christian Mythology’ and, inspired by H.G. Wells, consoled himself by

thinking (22):

‘To hell with these priests and their pseudo miracles and bloody sacrifices at the high altar and

their mysteries. They are always talking about the great mysteries of life; scientists talk about problems.’

This was not the only time that de Bruyne was to clash with the authorities at Lancing over what

he viewed as the religious fanaticism of the headmaster and the school’s governing body.

Nevertheless, his last year at Lancing was a particularly happy one. He was head of his

house and had the run of the laboratories. He even won the school essay prize, although the

master judging the prize ensured that the headmaster did not have an opportunity to read de

Bruyne’s irreverent winning essay!

De Bruyne left Lancing at the end of July 1923. However, he did return to speak at the

opening of the new ‘Advanced Science Laboratories’ in 1957 and his views of Lancing had

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clearly not changed over the years, although they were undoubtedly stated with more tact some

thirty years on.

CAMBRIDGE (VIA WEMBLEY)

In the early summer of 1923 de Bruyne learnt that he had passed his higher certificates in physics,

chemistry, mathematics and divinity, with a distinction in chemistry. These results excused him

from sitting the entrance examinations to read Natural Sciences at the University of Cambridge,

and hence gave him a summer to do as he wished. Instead of following the usual option of acting

as a tutor to pupils taking their school certificates, he obtained a summer job at the research

laboratories of the General Electric Company (G.E.C.) Ltd at Wembley. Whilst there in 1923 he

worked on using a Lummer-Brodhun photometer to measure the spatial distribution of

illumination from electric light fixtures. He found the environment exhilarating and spent three

summers working at Wembley. Indeed, his first paper (2), titled ‘The Electrostatic Capacity of

Aluminium and Tantalum Anode Films’, was published in the ‘Transactions of the Faraday

Society’ in 1927 with R.W.W. Sanderson of the G.E.C. from their work at Wembley on dry

batteries.

In October of 1923 de Bruyne went up to Trinity College, Cambridge, to read Natural

Sciences and in 1927 took part Two of the Natural Sciences Tripos and obtained a First. Whilst

an undergraduate at Cambridge he also found time to write a book (1) on the subject of ‘The

Electrolytic Rectifier: For Electrical Engineers, Physicists and Wireless Amateurs’, which was

published in 1924. Admittedly it was a short book. Indeed, in the preface he wrote:

‘A PREFACE is an apology and an excuse. I apologize for writing such a small book on so big a subject.

My excuse is that it is, I believe, the first book on the electrolytic rectifier.’

In the Summer of 1927 he returned to the research laboratories of the G.E.C. at Wembley

where he worked on the topic of field emission under B.S. Gosling. Thanks to him, de Bruyne

was able to return to Cambridge, in September 1927, with various items of vacuum equipment

with which to start his PhD research at the Cavendish Laboratories, under the supervision of Lord

Rutherford.

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However, de Bruyne chose not to work on Rutherford’s main area of interest, i.e.

radioactivity, since de Bruyne had decided to apply for a Prize Fellowship at Trinity as soon as

possible. He therefore selected a research topic which he felt could be completed and written up

in a year. The topic he elected to study was field emission, since the electric fields were rather

similar in magnitude to those developed across aluminium oxide films, which he had investigated

as a pupil at Lancing and later during his summers whilst working at the G.E.C. laboratories. (The

fact that he had acquired much of the necessary equipment for his field emission studies from his

summer months at G.E.C. suggests that this decision had been made well in advance of de

Bruyne taking up his research position at the Cavendish.) In 1928 de Bruyne published his

findings in the Proceedings of the Royal Society (4), the paper being communicated by

Rutherford, who commented that at least he now knew what de Bruyne had been up to for his

PhD studies!

De Bruyne also wrote up his research as a thesis for the Trinity Fellowship and in

September 1928 was duly elected a Prize Fellow of Trinity College, which gave him free rooms,

free dinner and four hundred pounds a year for four years. De Bruyne took his MA and PhD

degrees in 1930. He continued to work at the Cavendish on his favourite topic of field emission

(3-6), although Rutherford directed him to spend more time helping with the teaching and to use

his considerable experimental skills to make and test thyratron counters. Again his summers at

G.E.C. stood him in good stead, and de Bruyne made the first thyratron device to be used at the

Cavendish (7). However, de Bruyne’s reluctance to commit himself wholeheartedly to working

on radioactivity, no doubt combined with the fact that both he and Rutherford had very dominant

personalities, led to de Bruyne leaving the Cavendish in 1931.

Fortunately, Trinity College came to his rescue and invited de Bruyne to become Junior

Bursar, a post he assumed in September 1931. However, it seems clear that another factor in de

Bruyne’s decision to leave the Cavendish and academic research in physics was that during 1929

he had developed a passion for flying, which soon also became a passion for aircraft materials

and structural engineering. This turning point in de Bruyne’s life was initiated by the Reverend

Frederick Simpson, Fellow of Trinity, a history don and a well known eccentric, who offered him

a ride in his de Havilland Moth aircraft. This was kept at the newly-opened Marshall’s

Aerodrome run by David Marshall, and his son Arthur, at Fen Ditton on the Newmarket Road,

just outside Cambridge. De Bruyne was determined to learn to fly and obtained his pilot’s ‘A’

license (No. 9018) in 1929, going solo after 12 hours of instruction. He was the first pupil of the

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flying school run by the young Arthur Marshall. (Later Sir Arthur Marshall, OBE, DL and

founder, along with his father, of Marshall’s Aerospace and of Cambridge Airport, both of which

are essentially in the same location today, although somewhat larger in size. De Bruyne and

Arthur Marshall became close friends, and Marshall would later assist de Bruyne in difficult

times.) After obtaining his license, de Bruyne bought a de Havilland Moth aircraft (No. G-

AAWN) from Arthur Marshall. He stated it was at this moment that he changed from being a

physicist to an ‘engineer-entrepreneur’. The post of Junior Bursar (which de Bruyne defined as

like running a hotel, but without needing to worry about the catering side of the business) gave

him ample time to develop his interests in flying and aircraft engineering. Indeed, during his time

as Junior Bursar he established the Cambridge Aeroplane Construction Company in 1931, which

became Aero Research Ltd in 1934. In connection with this latter company he would make many

novel and major advances in the design and construction of aircraft structures, as discussed

below.

In 1937 de Bruyne decided to return to teaching and research, and also wished to spend

more time developing his fledgling company. He therefore resigned his College Bursar’s post and

became a College Lecturer and Demonstrator in the Engineering Laboratory of the University.

This entailed giving lectures on physics to first-year engineers and courses on plastics to senior

engineers, as well as becoming Director of Studies at Trinity. His research had now become

firmly focussed on aircraft structures and was inevitably linked to his interests in designing and

building novel aeroplanes and aircraft components. In 1944, de Bruyne realised that the war had

so changed his outlook on life that he resigned from his appointments as College Lecturer and

Fellow of Trinity College. He never returned to academic life, but thereafter devoted himself full-

time to his companies: Aero Research Ltd (formed in 1934, and to become part of the

multinational Swiss-owned CIBA organisation in 1947), Techne (Cambridge, UK) Ltd (formed in

1948) and Techne (New Jersey, USA) Inc. (formed in 1961).

THE ‘SNARK’

As mentioned above, following the granting of his pilot’s license in 1929, de Bruyne purchased

his own de Havilland Moth aircraft. He then spent the summer of 1931 at the de Havilland

Aeronautical Technical School as an owner-apprentice, where the basic elements of stress

distributions in aircraft structures were taught to the de Havilland Aircraft Company apprentices.

De Bruyne became convinced that there was considerable scope for the introduction of novel

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designs and materials in aircraft structures, especially since it seemed that anything but a biplane

was regarded as un-English and not really practical by the current aircraft design engineers. He

considered the Airworthiness Department of the Royal Aircraft Establishment (RAE) to be the

bastion of such entrenched orthodoxy.

Hence, in May 1930, in order to develop and demonstrate his ideas on aircraft design, de

Bruyne began work on a four-seat, low-wing monoplane. He named his plane the ‘Snark’, after

the mythical creature invented by Lewis Caroll.

The ‘Snark’ incorporated many of de Bruyne’s novel and controversial design aspects in

its structure, wings and fuselage (8,10). The detailed construction of the ‘Snark’ has been

reviewed by Riding (1998a) and the important feature was the use of stressed plywood skins as an

integral part of the structure, and not merely for the covering of the fuselage and wings. Further,

de Bruyne found, whilst investigating the use of plywood in aircraft, that structures made using

plywood stressed-skins could be made lighter without substantial loss of strength. He achieved

his weight-saving by careful orientation of the grain direction of very thin skins of plywood. This

provided efficient tension bracing, and so he could reduce the number and cross-section of

stiffeners to the bare minimum. This method of construction led to a very thick, but smooth,

cantilever-wing without the usual struts and wires for support. For predicting the collapse of the

wooden wing spars he used Prager’s analysis of plastic failure. In designing the wooden

monocoque fuselage he used Wagner’s tension field analysis. Employing these design features

and analyses, de Bruyne predicted that he could indeed combine high strength coupled with a low

weight in the ‘Snark’. For example, the fuselage alone was half the weight of that of a similar

conventional aircraft.

However, the Airworthiness Department of the RAE dismissed the whole design concept

and stated that they could not issue a certificate (so that the aircraft could be legally flown) for

such a lightweight structure, since such a lightweight structure must imply an inadequate strength.

The refusal of the RAE to accept de Bruyne’s designs led to an impasse which was only resolved

when K.T. Spencer (later Chief Scientist of the Ministry of Fuel and Power) persuaded the Head

of the RAE to purchase a ‘Snark’ fuselage (for £63 11s 9d) and test it to destruction. Such a

purchase was possible since de Bruyne had in the meantime been building the ‘Snark’. He began

this undertaking firstly by himself in a rented shed at Marshall’s Fen Ditton Aerodrome, having

obtained the necessary ground engineer’s and aircraft welder’s licenses, and then subsequently

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assisted by his first employee, George Newell. De Bruyne’s designs were completely vindicated

and on 21 June 1934, a week after the RAE test had been conducted, the design was approved.

On 16 December 1934 the ‘Snark’ (G-ADDL), with de Bruyne at the controls, made its maiden

flight from Marshall’s (Fen Ditton) Aerodrome. The aircraft received its full ‘Certificate of

Airworthiness’ on 26 April 1935. The aircraft was later bought by the Air Ministry for research

tests which included studies of the aerodynamic effects of thick-wing monoplanes. The ‘Snark’

was destroyed in a Luftwaffe attack on Croydon Aerodrome on 15 August 1940.

It is noteworthy that de Bruyne’s designs could be translated into a practice only because

an important development in the manufacture of plywood had taken place shortly prior to him

starting work on the ‘Snark’. This was the replacement of natural resins, such as casein (a by-

product of milk) and blood-albumen, for bonding the plies together by a synthetic resin based

upon phenol-formaldehyde. The natural resins were very prone to degradation by ingressing

moisture, whilst the plywood manufactured using phenol-formaldehyde resin was very resistant

to such attack. Also, the plywood manufactured using phenol-formaldehyde was far stronger and

possessed a significantly higher modulus. De Bruyne was aware of these potential advantages of

the latest type of plywood, and made full use of them when he designed and built the ‘Snark’

using plywood based upon phenol-formaldehyde resin. Also, undoubtedly, the experience he

gained on synthetic resins whilst building the ‘Snark’ was to lead directly to de Bruyne being

becoming a pioneer, not only in the design of aircraft, but also in the materials and methods used

in their construction.

THE ‘CAMBRIDGE AEROPLANE CONSTRUCTION COMPANY’

AND ‘AERO RESEARCH LTD’

During the course of building the ‘Snark’, and whilst a Junior Bursar at Trinity, in 1931 de

Bruyne formed the Cambridge Aeroplane Construction Company in order to develop and

demonstrate his ideas, and allow him to act as a freelance consultant to other companies. As noted

above, the company was initially based in a shed rented at the Marshall’s Aerodrome on the

Newmarket Road, to which he would cycle every afternoon. On 7 April 1934, the name of the

company was changed to Aero Research Ltd and in May 1935 the company moved to the

outskirts of Duxford, a small village about eight miles south of Cambridge, where de Bruyne

bought a flat, fifty-acre field and erected a second-hand steel-framed hangar. The official opening

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ceremony took place on Saturday 3 October 1936, just after the first expansion in the company’s

facilities at Duxford had been completed.

THE ‘LADYBIRD’

Following on from the ‘Snark’, de Bruyne started work on a second unorthodox-looking

aeroplane, called the ‘Ladybird’. In 1936, he and George Newell began to construct the

‘Ladybird’ which was a mid-wing, single-seat machine with a tri-cycle undercarriage and a semi-

tapered twisted wing (Riding (1998)). The plywood-covered monocoque fuselage was of oval

section. It was naturally a monoplane and each wing was a single-spar structure with plywood-

covered leading edges to retain torsional rigidity. The all-wood cantilever tailplane had all the

controls enclosed and the fin was built integral with the fuselage. It was intended to be a light,

low-cost machine. However, de Bruyne realised that his original financial plans for the

‘Ladybird’ were not feasible (Garnsley (1992)). There were large numbers of small aircraft

companies competing for a market limited by the poor economic situation in that time and that

the capital required to move to higher volume, lower cost production was far beyond him. He sold

the partly finished machine to a young Dutchman, J.N. Maas, who completed its construction.

The ‘Ladybird’ (G-AFEG) made its maiden flight, piloted by Robert Doig, from the Marshall’s

new Cambridge Airport, at Teversham (close to the original Fen Ditton site), on 6 January 1938.

The ‘Ladybird’ is thought to be still in existence, in a barn somewhere near Peterborough.

‘AEROLITE’ COMPOSITE MATERIALS

Another reason why the work on the ‘Ladybird’ was stopped was that in 1936 de Bruyne was

approached by the de Havilland Aircraft Company. He was asked to act as a consultant to them,

through Aero Research Ltd, to investigate the possibilities of using reinforced phenol-

formaldehyde resins for making variable-pitch propellers. A major reason for this approach was

that de Bruyne had decided back in 1934 that a main objective must be to get Aero Research Ltd

known to the aircraft companies. To achieve this, he decided to write a number of articles for the

general technical press, rather than learned scientific journals. Hence, he published a series of

articles in the ‘Aeroplane’ and ‘Aircraft Engineering’. These articles arose from his work on the

‘Snark’, and were on such themes as the use of plywood (8), bolted joints in wood (9), the design

of the box fuselage (10) and the creep of plastics used for aircraft propellers (11). The

‘advertising campaign’ was successful and led to Geoffrey de Havilland initiating contact

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between his company and de Bruyne. The outcome of this was that de Bruyne visited the de

Havilland Aircraft Company at Hatfield on 9 April 1936, from which he returned with a first

cheque for £1000 as an advance for his consulting and research services on reinforced plastics for

aircraft propellers. (The attraction of using a reinforced plastic was that its density was about one-

half that of aluminium alloy so that the centrifugal force at the root end of a propeller was

correspondingly reduced.) He later recorded that:

‘As I drove back the heavens opened wide to reveal a chorus and trumpets making Handel-like

noises.’

The support of the de Havilland Aircraft Company was crucial to the success of de

Bruyne, and his company. He not only received a regular income for Aero Research Ltd for its

research and development work, but he also became firm friends with C.C. Walker, the Chief

Engineer at de Havilland whom he regularly visited on Friday afternoons to exchange ideas. His

work with the de Havilland Company led to de Bruyne (13) presenting, on 28 January 1937, a

paper to the Royal Aeronautical Society entitled ‘Plastics Materials for Aircraft Construction’. In

this lecture he demonstrated that phenolic resins with suitable reinforcement could have the

necessary mechanical properties for aircraft construction, and also the potential to produce lower-

weight components. During the course of the lecture he introduced the term ‘Aerolite’ to denote

phenolic resins which were reinforced with a continuous reinforcement. This paper won him the

Society’s Simms Gold Medal for 1937.

De Bruyne now needed to prove that components, and in particular propellers, could be

manufactured. Hence, he purchased some second-hand hydraulic presses with a platen area large

enough to press a reinforced phenol-formaldehyde blank, which could afterwards be machined to

the required shape in a similar manner to a wooden blade. However, he was unsuccessful in

producing a uniformly crosslinked block of material due to its considerable thickness, and the

project was stopped. At the suggestion of a Mr. Gordon, an undergraduate at Trinity College

whose family were in the linen business, de Bruyne tried flax roving which was teased out into

flat bands as the reinforcement. This produced a remarkably strong and light-weight composite,

which was called ‘Gordon Aerolite’. Its properties were good along the grain but poor at right

angles, so laminated sheets were made with crossed-grain directions, as in plywood. Although

‘Gordon Aerolite’ was never commercialised, it did provide de Bruyne’s company with useful

development and production contracts. The first contract was from the Air Ministry and was for a

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full-scale wing-spar for the Bristol ‘Blenheim’ aircraft. This presented a major challenge, since

the largest piece of ‘Gordon Aerolite’ which had been made so far was eight inches in length, but

the ‘Blenheim’ spar needed to be some thirty feet in length. It was made in a specially designed

press that took in the material in three-foot ‘bites’. This press was being made in Dusseldorf,

Germany, during the Autumn of 1938 with the threat of war clearly evident. Thus, whilst

Chamberlain was conferring with Hitler at Bad Godesberg, de Bruyne flew to Dusseldorf to

ensure the safe arrival of his press before war broke out. He arranged for the makers to deliver the

press, untested and unassembled, to mutual friends in Holland. Such steps were not, of course,

necessary; and the press arrived at Duxford a month later.

The good properties of ‘Gordon Aerolite’, coupled with the potential shortage of

aluminium, led to another contract for a one-off ‘Spitfire’ fuselage (17). In the event, the

composite ‘Spitfire’ was not needed, but thirty Miles ‘Magister’ tail-planes were successfully

constructed. Hence, ‘Gordon Aerolite’ was the first synthetic structural composite material to be

seriously used in the construction of aircraft. A report in 1940 from the Royal Aircraft

Establishment stated:

‘It is considered that this material is the most promising organic sheet material yet produced for

stressed skin covering for aircraft and it appears that, if available in quantity, it could be used to directly

replace Duralumin in existing designs’.

‘AEROLITE’ ADHESIVE

The research contracts for ‘Gordon Aerolite’, and his consulting for de Havilland, as well as his

appointment at Cambridge University, kept Aero Research Ltd alive financially, but only just! So,

in 1937, soon after giving up his plans for an aircraft construction company, based upon making

the ‘Ladybird’ aeroplane, the area he now chose in order to inject money into his company was

the development and production of synthetic urea-formaldehyde based adhesives. Why he chose

this area is not completely clear. However, he did have direct experience of the severe

shortcomings of the casein adhesives, then typically used to bond plywood in aircraft, and in

other applications. Casein is a natural material and is a by-product of milk, and worked well,

except when the joints were exposed to a moist environment and the adhesive absorbed water.

The adhesive then became very mechanically weak and smelt of old camembert cheese.

(However, engineers are a cunning breed, since they used this fact as an early form of non-

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destructive test. The aircraft engineers routinely smelt the bonded parts of the aircraft, and when

the joints smelt of old camembert cheese they knew that the adhesive joints were about to fall

apart, and that the adhesive should be replaced!) It will be recalled that, during the building of the

‘Snark’, de Bruyne had noted (8) the poor durability of casein resins for the manufacture of

plywood. Indeed, a Dr. A.H. Wilson, also a Fellow of Trinity College, remarked to de Bruyne

that of all the industries the one that seemed to him to have the most potential for growth was the

chemical industry. Also, the choice of urea-formaldehyde was possibly made since earlier work

in Germany had indicated that adhesives based upon such resins had good intrinsic adhesion.

Further, working on urea-formaldehyde based adhesives would not clash with his consulting

work for de Havilland on composite materials based upon phenolic resins (12, 13).

In any event, in early 1937, de Bruyne commissioned a Dr. R.E.D. Clark of the

Chemistry Department of Cambridge University to act as a consultant and produce experimental

urea-formaldehyde resins for evaluation by Aero Research Ltd. The encouraging test results led

to the building of a pilot plant to produce such resins and they were given the name ‘Aerolite’. On

22 April 1937, after tests had been conducted on wooden propellers which were bonded using

‘Aerolite’ adhesive, the Air Ministry officially approved ‘Aerolite’ for use in aircraft. In May of

that year it was exhibited for the first time at the Royal Aeronautical Society’s garden party held

in the original Heathrow Airport hangar. Also, in May 1937, ‘Aerolite’ urea-formaldehyde

adhesives were launched into the market place. Sales grew slowly and ‘Aerolite’ adhesive was

initially struggling to pay its way. However, in 1939 a method for in-line quality assessment was

introduced, so that a consistent product could be produced, and it was discovered that formic acid

acted as a catalyst to give a significant improvement in the gap-filling abilities of the adhesive.

Thereafter, the use of ‘Aerolite’ steadily expanded. The furniture industry was quick to realise the

advantages that it offered, especially for increasing production rates, and during the war years

‘Horsa’ gliders and ‘Mosquito’ fighter-bombers, as well as other wooden aircraft and naval

vessels, were produced using ‘Aerolite’ adhesives.

During the early 1940’s, de Bruyne invented a process known as ‘strip-heating’, which

was a method for reducing the curing time of ‘Aerolite’ adhesives from hours to minutes. This

involved the use of metal straps that were applied to the joint to be bonded and through which a

very high current was passed at a low voltage. Twenty-seven companies used strip-heating and

many millions of pounds worth of equipment were bonded this way. In 1950, after a legal

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wrangle, de Bruyne was awarded £1000 for his invention by the Royal Commission on Awards,

but of this £800 went on his legal bills.

‘Aerolite’ urea-formaldehyde adhesives are still in production and are standard wood-

working adhesives.

SANDWICH PANELS

It will be recalled that, whilst all the activities described above were taking place at Aero

Research Ltd, de Bruyne was also a College Lecturer and Demonstrator in the Engineering

Laboratory of the University. His research work in these laboratories was mainly concerned with

sandwich structures which consisted of a light-weight core, such as balsa wood, with metal skins.

In 1940 de Bruyne, along with G.S. Gough, C.F. Elam (Mrs. G.H. Tipper) of the Cambridge

University Engineering Laboratory, published (14) a detailed analysis of such sandwich structures

in the Journal of the Royal Aeronautical Society. De Bruyne’s interest in such novel structures

undoubtedly arose from his regular Friday afternoon discussions with C.C. Walker of the de

Havilland Company. Walker had adopted balsa-core/plywood-skins sandwich panels for the

‘Comet’ of 1934 and the ‘D.H. 91 Albatross’ airliner of 1937, and this type of sandwich panel

would also be used in future designs such as the ‘Mosquito’. The paper in the Journal of the

Royal Aeronautical Society considers the deformation and strength of sandwich panels under a

compressive load. It demonstrated that (i) wrinkles in the skins occurred under the compressive

loads and (ii) that their wavelength was inversely proportional to the cube root of the elastic

modulus of the material of the skins. This suggested to de Bruyne that a honeycomb core would

also be very efficient as the core material, provided that the cells were smaller than the

wavelength of the wrinkles. Indeed, in 1938 a page of de Bruyne’s notebook reveals a sketch for

a tailplane of an aircraft using an hexagonal honeycomb-core with bonded skins. Also, from his

notes, it appears that honeycomb sandwich panels were made by de Bruyne and his colleagues at

Duxford during the early 1940s, using the newly-invented ‘Redux’ adhesive, see below.

De Bruyne saw his ideas being used on a large scale when he visited aircraft companies

in the United States in 1952. He certainly believed that this was a direct result of the British

Government disclosing his ideas to the United States authorities, as occurred with many British

inventions upon the entry of the USA into the Second World War. Upon his return from the USA,

he established a bonded-honeycomb structures group, of Aero Research Ltd, at Duxford. The

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research, development and production of such structures still continues at Duxford (now under

the name ‘Hexcel Composite Materials’) for aircraft such as all the ‘Airbus’ and ‘Boeing’

airliners, as well as for a wide range of other industries.

‘REDUX’ ADHESIVE

By the 1941 several developments had occurred which led to de Bruyne making one of his most

major and novel contributions in the area of adhesion and adhesives. On the technical front, de

Bruyne had demonstrated that ‘Gordon Aerolite’ composites offered an alternative to aluminium

alloy for aircraft structures, but had found no suitable adhesives for the material. Further, he had

demonstrated the theoretical and practical viability of sandwich panels for aircraft components,

but when metal skins were used he knew of no suitable adhesives. Indeed, on this later point,

following his work with Gough and Elam (14), he wrote to the Aeronautical Research Committee

in 1941:

‘ … the conclusion from these notes is that a balsa fuselage covered on both sides with Duralumin

should be an extremely efficient structure. Its manufacture would only be possible if the adhesion problem

of adhesion between balsa and Duralumin were satisfactorily solved.’

Also, he now found that he had some spare time on his hands. This arose from de

Havilland ending the research association with Aero Research Ltd, since they were far too busily

involved with urgent war work and they saw that reinforced plastics would not be of immediate

use. Further, a dispute with the Ministry of Aircraft Production led to the cancellation of the

development and production work on ‘Gordon Aerolite’ composites. (This combination of events

could have led to financial disaster, since ‘Aerolite’ urea-formaldehyde adhesive had yet to

provide significant income to the company. However, Aero Research Ltd was kept going

financially by his old friend Arthur Marshall (1994). He arranged for de Bruyne’s company to

undertake repair work of the wooden Airspeed ‘Oxford’ aircraft, the standard twin-engine trainer,

and later on other aircraft types.)

Thus, de Bruyne and George Newell set about developing an adhesive to resolve the

problems of bonding metals, and within six months were successful. Their starting points were,

firstly, an appreciation from their earlier studies of the fundamental science and technology of

adhesion and adhesives (15,16). Secondly, the recognition, from their work on ‘Aerolite’

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adhesives, that whilst such urea-formaldehyde based adhesives were excellent for wood, they

were poor for bonding metals. Thirdly, the observation that components made from ‘Gordon

Aerolite’ phenolic-based composites had a very strong tendency to adhere very well to the metal

moulds in which the components where manufactured, unlike the simple, unfilled phenolic resin

which formed the matrix of the composite. This observation was considered by de Bruyne to arise

from the use of flax fibres in the ‘Gordon Aerolite’, which not only reinforced the inherently

brittle phenolic resin but also assisted the escape of water vapour and other volatiles, which are

released during the cure reaction. However, any suitable adhesive would require a reinforcement

that was simpler to use than flax fibres; for example, such fibres would result in too high a

viscosity and would require relatively high bonding pressures.

It occurred to de Bruyne that replacement of the flax reinforcement by poly(vinyl formal)

might be worth trying, since this polymer has a relatively high softening point, was known to be

compatible with phenolic resins and was thought to be able to ‘soak up water’ that was released

during cure of the phenolic. Initially, solutions of the potential adhesives were prepared that

consisted of blends of poly(vinyl formal) and phenol-formaldehyde resole resins, but without

great success. Films of the adhesives were then prepared, where a thin film of the poly(vinyl

formal) was first cast from solution and the phenolic resin coated onto both sides of the

poly(vinyl formal) film, a de Bruyne or Newell finger being used for this purpose. The coated

film was then dried and used to prepare single-lap joints using aluminium alloy as the substrates.

The lap joints were then tested in tension. December 5 1941 saw the optimisation of this process

with breaking stresses of 1250 lbs/in2 being recorded, and the first modern, synthetic structural

adhesive for bonding metals had been invented. It was christened ‘Redux’ adhesive, standing for

Research at Duxford. Various subsequent developments followed and many patents were granted

to de Bruyne and his colleagues. The detailed development work that led to the invention of

‘Redux’ has been excellently described recently by Bishopp (1997).

The first practical application of ‘Redux’ adhesive was, however, not in aircraft but in

tanks. ‘Redux’ was used to bond thousands of ‘Cromwell and ‘Churchill’ tank clutch plates. The

bonded version was found to give a tenfold increase in life compared with the riveted plates.

Indeed, it was not until 28 July 1944 that the first ‘Redux’ bonded structural components in an

aircraft made their maiden flight in the de Havilland ‘Hornet’. This aircraft possessed a light-

weight, but very strong wing, which was made possible by using ‘Redux’ to bond aluminium-

alloy flanges to balsa-wood webs to form the ribs and spars. The naval version, the ‘Sea Hornet’,

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also had the first metal-to-metal structural joints: aluminium-alloy sheets were bonded together to

strengthen the attachment points for the tail wheel and arrestor hook to the rear fuselage

bulkhead.

In 1946 the de Havilland ‘Dove’ became the first all-metal aircraft designed for bonding

using ‘Redux’ adhesive. Apart from the use of ‘Redux’ adhesive, another important aspect of the

successful use of adhesive bonding was de Bruyne’s recognition of the need to pretreat the

surface of the aluminium-alloy prior to bonding by using a chemical-etch process. He chose a

pretreatment that had been originally developed as a pretreatment for painting. The use of

‘Redux’ adhesive, coupled with this chemical-etch pretreatment process, proved to be an

outstanding combination, both in terms of the very good initial mechanical performance of the

adhesive joints as well as giving excellent long-term durability to water, de-icing fluid, aircraft

fuels, etc. In the ‘Dove’, ‘Redux’ was used throughout for attaching stringers in the fuselage and

wings, as well as for local reinforcements where several plates of aluminium alloy were bonded

together. Apart from improved strength and longer fatigue life compared with riveted structures,

the ‘Redux’ bonding method also gave aerodynamically-clean external surfaces and enabled

considerable cost savings to be made in production.

The next major challenge for ‘Redux’ bonding was the de Havilland ‘Comet’, the world’s

first jet airliner. From the outset it was decided to use ‘Redux’ adhesive on an ambitious scale,

since aerodynamically-clean external surfaces were very important for an aircraft which would

raise cruising speeds by about 200 mph. The high-altitude flying would also pose problems of

pressurisation which could be solved far more easily by bonding, as opposed to riveting with its

need for the subsequent sealing of each hole. Most importantly of all, the use of ‘Redux’ bonding

enabled a large saving in weight to be achieved without a loss in strength, and its principal role

was to ensure that an economic payload was achieved. Following the accidents to the ‘Comet’, a

public enquiry was held at which adverse criticism was made of the use of ‘Redux’ adhesive.

However, on 1 February 1955, the Commissioner, Lord Cohen, presented his report which

completely exonerated ‘Redux’ as contributing in any way to the accidents. Indeed, on the later

‘Comet 4’ aircraft, ‘Redux’ was employed even more extensively.

The list of aircraft which have employed ‘Redux’ adhesives is extremely long, with other

applications including hovercraft and Donald Campbell’s world-speed car, ‘The Bluebird’.

‘Redux’ adhesives, based upon of poly(vinyl formal) and phenol-formaldehyde resole resins, are

17

still widely used today in the construction of aircraft, especially in locations where the joints are

likely to be exposed to particularly hostile environments. Since their durability are still considered

to be outstanding, even when compared with the more modern, epoxy-based, adhesives.

Finally, it is of interest to note that de Bruyne reverted to being an educator again in the

early 1950s. To help promote the advantages of ‘Redux’ adhesive bonding he founded ‘Summer

Schools’, typically held in the Engineering Department of Cambridge University. At these, he and

other experts in this newly developed, multi-disciplined, area of adhesive bonding gave lectures

and demonstrations on topics such as the fundamentals of adhesion, the importance of surface

pretreatment of the substrates, the chemistry of adhesives, production techniques and the design

and testing of adhesive joints (18-21). Of course, not only did he and his colleagues educate the

aircraft engineers that attended, but he also sold more glue to the industry!

LATER YEARS

By 1946, export sales, especially of ‘Aerolite’, accounted for three-quarters of the income of

Aero Research Ltd and a new factory was urgently needed to meet the increasing demand for

their products. Thus, to acquire the adequate injection of capital, and hence assure the future

growth of the Company, in November 1947 Aero Research Ltd became part of the Swiss-owned,

multinational, CIBA organisation. It was a difficult decision for de Bruyne to sell the Company

which he had founded and nurtured through many difficult times. However, he became the

Managing Director when he sold Aero Research Ltd to CIBA, until his retirement in 1960. (Aero

Research Ltd was re-named CIBA (ARL) Ltd in June 1958.) As mentioned above, the ‘Snark’

was destroyed in 1940, but at least one component survived: to mark the occasion of de Bruyne’s

retirement from CIBA (ARL) Ltd he was presented with a propeller from the ‘Snark’ by George

Newell.

However, he still had other activities to keep him busy. In August 1948 he had founded a

company to make and sell scientific instruments, Techne (Cambridge) Ltd. In 1961 Techne Inc.

was also established in the USA at Princeton. Again his inventiveness shone through, and many

novel instruments were patented and marketed. Also, after his retirement from Ciba (ARL) Ltd,

he became a non-executive director of Eastern Electricity from 1962 until he resigned in 1967.

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The reason for his resignation in 1967 was that he decided the Labour Government then

in power had removed all incentive and hope for the lone inventor and entrepreneur. So he

decided to emigrate to the USA, and he set out his reasons for emigrating in a letter which he sent

to about fifty leading scientists and industrialists. This resulted in a meeting with the Rt. Hon.

Tony Benn, then the Minister of Technology. However, this meeting, as well as many requests to

stay from friends, failed to change his mind. So, on 31 March 1967 de Bruyne and his wife, Elma

Lillian Marsh whom he had married in 1940, set sail for New York. In the USA he was active in

connection with Techne Inc., and became an American Citizen on 10 November 1972. However,

in 1991 he did return to live permanently in Britain, very close to the site at Duxford where he

had made the inventions and produced the adhesives which changed forever the thinking of

aircraft designers.

ACKNOWLEDGEMENTS

The author wishes to thank Professor K.W. Allen, Mr. J. Bishopp, Ms. A.C. de Bruyne, Mr. W.A

Dukes, Dr. P. Stark and Professor D. Tabor, FRS, for many helpful comments and suggestions

during the preparation of the present Memoir. He would also like to acknowledge the assistance

of Ms. S. Pressel in locating many of the papers and patents cited.

REFERENCES TO OTHER AUTHORS

Bishopp, J.A. 1997 The history of ‘Redux’ and the ‘Redux’ bonding process.

Int. J. Adhesion and Adhesives, 17, 287-301.

Garnsley, E. 1992 An early academic enterprise: A study of technology transfer.

Business History, 34, No.4, 79-98.

Marshall, Sir A. 1994 The Marshall story. Somerset: Patrick Stephens Ltd.

Riding, R. 1998 De Bruyne’s flying beetle. Aeroplane Monthly, March, 36-38.

Riding, R. 1998a Aero Research Snark. Aeroplane Monthly, November, 694-698.

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BIBLIOGRAPHY

(1) (1) 1924 The electrolytic rectifier: For electrical engineers, physicists and

wireless amateurs. London: Sir Isaac Pitman & Sons, Ltd. (2) (2) 1927 (With R.W.W. Sanderson) The electrostatic capacity of aluminium and

tantalum anode films. Trans. Faraday Soc. 23, 42-51. (3) (3) 1928 Some experiments on the auto-electronic discharge. Phil. Mag. 5, 574-

581. (4) (4) The action of strong electric fields on the current from a thermionic

cathode. Proc. R. Soc. A 120, 423-437. (5) (5) Note on the effect of temperature on the auto-electronic discharge. Proc. Cambridge Phil. Soc. 24, 518-520. (6) (6) 1930 The temperature dependence of field currents. Physical Review 35, 172-176 (7) (7) 1931 (With H.C. Webster) Note on the use of a thyratron with a geiger

counter. Proc. Cambridge Phil. Soc. 27, 113-115. (8) (8) 1934 Plywood construction for aeroplanes. The Aeroplane June, 901-904. (9) (9) 1935 Bolted joints in wood – the estimation of the strength of bolted

connexions in wooden aeroplanes. The Aeroplane February, 39-40. (10) (10) (With K. Kennedy) The rigidity of a box fuselage. The Aeroplane

November, 665-667. (11) (11) 1936 Improving the creep stress of plastics. The Aeroplane February, 231-232. (12) (12) (With J.N. Maas) A property of synthetic resins – materials which are extremely resistant to disintegration from shocks and vibrations. Aircraft

Engineering October, 289-290. (13) (13) 1937 Plastic materials for aircraft construction. Proc. Royal Aeronautical Soc. 523-590.

20

(14) (14) 1939 (With G.S. Gough and C.F. Elam) The stabilisation of a thin sheet by a continuous supporting medium. J. Royal Aeronautical Soc. XLIV,

12-43. (15) (15) The nature of adhesion. The Aircraft Engineer XVIII, December, 52-54. (16) (16) 1940 Solid organic materials used in engineering. Aircraft Engineering May-August, 2-12. (17) 1942 ‘Plastel’: A new method of increasing flexural stiffness. British Plastics

14, 306-316. (18) 1944 The strength of glued joints. Aircraft Engineering April, 115-118. (17) (19) 1945 Fighter fuselage in plastic. Aircraft Production July, 323-326. (20) 1947 The physics of adhesion. J. Scientific Instruments 24, 29-35. (18) (21) 1951 (With R. Houwink) Adhesion and adhesives. (Eds.) The Netherlands:

Elsevier. (19) (22) (With C. Mylonas). Static problems. Elsevier, 90-143, in Adhesion and

adhesives. Eds. N.A. de Bruyne and R. Houwink, Elsevier. The Netherlands: Elsevier, 1951.

(20) (23) The physical testing of adhesion and adhesives. Elsevier, 463-494. in

Adhesion and adhesives. Eds. N.A. de Bruyne and R. Houwink. The Netherlands: Elsevier, 1951.

(21) (24) 1957 Fundamentals of adhesion. Bonded aircraft structures. Cambridge:

Bonded Structures Ltd, Duxford, 1-16. (25) How glue sticks, Nature 180, 262-266. (26) 1980 Pioneering times, Proc. of Conf. on ‘Adhesives for Industry Technology

Conference’, El Segundo, California. (22) (27) 1996 My life. Cambridge: Midsummer Books.

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PATENT BIBLIOGRAPHY

British Patent 470,331 Improvements relating to the manufacture of material and articles from

resinous substances Inventor(s): N.A. de Bruyne, of Aero Research Ltd,

and The de Havilland Aircraft Company Ltd. Application Date: January

31, 1936. Filing of complete specification: November 20, 1936.

Complete specification accepted: August 3, 1937.

British Patent 488,373 Improvements relating to reinforcement of synthetic resinous materials

and objects. Inventor(s): N.A. de Bruyne, of Aero Research Ltd, and The

de Havilland Aircraft Company Ltd. Application Date: January 8, 1937

and November 12, 1937. Filing of complete specification: December 17,

1937. Specification accepted: July 6, 1938.

British Patent 501,649 Improvements relating to the reinforcement of synthetic resinous

materials and objects. Inventor(s): N.A. de Bruyne, of Aero Research

Ltd, and The de Havilland Aircraft Company Ltd. Application Date;

August 26, 1937 and March 31, 1938. Filing of complete specification:

August 23, 1938. Specification accepted: February 27, 1939.

British Patent 518,233 Improvements in and relating to joints in stressed structures. Inventor(s):

N.A. de Bruyne, of Aero Research Ltd. Application Date: August 18,

1938. Filing of complete specification: August 17, 1939. Complete

specification accepted: February 21, 1940.

British Patent 540,404 Improvements in or relating to composite articles and component parts

therefor. Inventor(s): N.A. de Bruyne and C.A.A. Rayner, of Aero

Research Ltd, and The de Havilland Aircraft Company Ltd. Application

Date: October 23, 1939. Filing of complete specification: October 11,

1940. Complete specification accepted: October 16, 1941.

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British Patent 540,442 Improvements in or relating to synthetic resin adhesives or cements.

Inventor(s): N.A. de Bruyne and C.A.A. Rayner, of Aero Research Ltd,

and The de Havilland Aircraft Company Ltd. Application Date; October

13, 1939. Filing of complete specification: September 27, 1940.

Complete specification accepted: October 17, 1941.

British Patent 544,845 Improvements in or relating to laminated structures. Inventor(s): N.A.

de Bruyne. Application Date: July 22, 1940. Filing of complete

specification: May 7, 1941. Complete specification accepted: April 30,

1942.

British Patent 544,878 Improvements in or related to laminated structures. Inventor(s): N.A. de

Bruyne. Application Date: July 22, 1940 (Divided out of No. 544,845).

Filing of complete specification: May 7, 1941. Complete specification

accepted: April 30, 1942.

British Patent 544,879 Improvements in perforating apparatus. Inventor(s): N.A. de Bruyne.

Application Date: May 7, 1941 (Divided out of complete specification of

No. 544,845). Complete specification accepted: April 30, 1942.

British Patent 549,496 Improvements in or relating to synthetic resin adhesives. Inventor(s):

N.A. de Bruyne and D.A. Hubbard, of Aero Research Ltd. Application

Date: May 19, 1941 and October 13, 1941. Filing of complete

specification: May 5, 1942. Specification accepted: November 24, 1942.

British Patent 565,490 Improvements in or relating to urea-formaldehyde condensation

products. Inventor(s): N.A. de Bruyne, of Aero Research Ltd.

Application Date: January 4, 1943. Filing of complete specification:

January 4, 1944. Complete specification accepted: November 14, 1944.

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British Patent 557,358 Method and apparatus for measuring the amount of coating material

applied to a surface. Inventor(s): N.A. de Bruyne. Application Date:

April 14, 1942. Filing of complete specification: April 9, 1943.

Complete specification accepted: November 17, 1943.

British Patent 577,823 Improvements in or relating to methods of bringing about adhesion

between surfaces. Inventor(s) N.A. de Bruyne. Application Date: May 4,

1942. Filing of complete specification: April 23, 1943. Complete

specification accepted: June 3, 1946.

British Patent 578,264 A method of producing cellular resin materials. Inventor(s): N.A. de

Bruyne. Application Date: December 10, 1941. Filing of complete

specification: December 9, 1942. Complete specification accepted: June

21, 1946.

British Patent 577,790 Improvements relating to the manufacture of light non-metallic

structural material or components. Inventor(s): N.A. de Bruyne, of Aero

Research Ltd, and The de Havilland Aircraft Company Ltd. Application

Date: August 29, 1938 and October 31, 1938. Filing of complete

specification: August 8, 1939. Complete specification accepted: May 31,

1946.

British Patent 645,073 Improvements in or relating to devices for maintaining a constant fluid

pressure. Inventor(s): N.A. de Bruyne. Application Date: January 28,

1948. Filing of complete specification: October 20, 1948. Complete

specification published: October 25, 1950.

British Patent 698,641 Improvements in or relating to microscopes and illuminating systems

therefor. Inventor(s): N.A. de Bruyne. Application Date: April 2,

1951. Filing of complete specification: March 14, 1952. Complete

specification published: October 21, 1953.

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British Patent 762,471 Improvements in bonding processes using urea-formaldehyde resin

glues. Inventor(s): N. A. de Bruyne and F. Bird, of Aero Research Ltd.

Application Date: May 26, 1953. Filing of complete specification: June

15, 1954. Complete specification published: November 28, 1956.

British Patent 765,466 Improvements in or relating to methods of bringing about adhesion

between surfaces. Inventor(s): N.A. de Bruyne, G.S. Newell and K.R.

Perry. Assigned to Aero Research Ltd. Application Date: December 10.

1953. Filing of complete specification: November 23, 1954. Complete

specification published: January 9, 1957.

British Patent 773,977 Improvements in or relating to thermostats. Inventor: N.A. de Bruyne.

Assigned to Techne Ltd. Application Date: October 26, 1953. Filing of

complete specification: January 26, 1955. Complete specification

published: May 1, 1957.

British Patent 776,973 Improvements in or relating to the manufacture of honeycomb cell

structures. Inventor(s): N.A. de Bruyne. Assigned to Aero Research Ltd.

Application Date: February 23, 1954. Filing of complete specification:

February 3, 1955. Complete specification published: June 12, 1957.

British Patent 985,154 Improvements in box-like casings. Inventor(s): N.A. de Bruyne.

Assigned to Techne Ltd. Application Date: June 18, 1963. Filing of

complete specification: March 17, 1964. Complete specification

published: March 3, 1965.

British Patent 986,433 Improvements in ovens for heating previously cooked meals. Inventor(s):

N.A. de Bruyne. Assigned to Techne Ltd. Application Date: August 3,

1962. Filing of complete specification: August 2, 1963. Complete

specification published: March 17, 1965.

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British Patent 998,614 Improvements in thermostatic controllers. Inventor(s): N.A. de Bruyne.

Assigned to Techne Ltd. Application Date: March 1, 1963. Filing of

complete specification: February 17, 1964. Complete specification

published: July 14, 1965.

US Patent 2,499,134 Method of providing adhesion between surfaces. Inventor(s): N.A. de

Bruyne. Assigned to Rohm & Haas Company. Filed November 29,

1944. Patented February 28, 1950. Equivalent Patent GB 565,793.

US Patent 2,872,365 Self-sustaining adhesive sheet and process for producing the same as

well as for uniting surfaces with it. N.A. de Bruyne, G. Saunders, K.R.C.

Perry. Assigned to Ciba Ltd. Application December 8, 1954. Patented

February 3, 1959.