Ceramics

B. S.

1913

trMTV.OWj:j!::ujs:":>js

THE UNIVERSITY

OF ILLINOIS

LIBRARY

Digitized by the Internet Archive

in 2013

http://archive.org/details/chromiumcolorsatOOrand

CHROMIUM COLORS AT LOW TEMPERATURES

BY

CHARLES CLAFLIN RAND

MARTIN ROBERT HORNUNG

THESIS

FOR THE

DEGREE OF BACHELOR OF SCIENCE

IN

CERAMICS

COLLEGE OF SCIENCE

UNIVERSITY OF ILLINOIS

1913

\ \ o

UNIVERSITY OF ILLINOIS

^\CVV^3D\k,19l3

THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BY

ENTITLED

IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE

DEGREE OF Q> OUC^UJv^V fr^ %AaJO\a^JL^ ^UkAAA^^J

Instructor in Charge

APPROVED

HEAD OF DEPARTMENT OF ^AAM^le^-

24650

UIUC

1.

1 2In the work done "by Buettner and Berge^ it was shown that

Cr Og imparts a green color to the glaze when it functions "basic

and red when it functions acid. "Buettner's red chromium glace was

.9 PbO ) f

) .2 Cr ( .6 SiOo . He gives the limiting SiO con-.1 X

£)

2 5(

' 2

tent as one equivalent and states that small amounts of Al o do not

affect the color. Berge gives a "brick red' PhO ) .15 Al 0„2

{ 0.6 SiO,) .05 Cr 0,7

2 °

and as a "brilliant red PhO) .1 Al o 0„J

)

B c{ 0.6 SiO

) .05 Cr P 0„2

Our investigations were carried out for the purpose of confirming

these limits or determining new ones. Also, to determine the ef-

fect of replacing part of the lead "by calcium, magnesium, harium,

and z in c

.

Croup I

.

In this group the RO and Alg0g remain constant, the SiO^ and

Cr "being variables. The limits covered were:E o

) 0.1 Al p0„ f

PhO )* °

( 0.5 to 1.9 Si0 9) .02 to 0.2 Cr

2 f

^

1. Sprechsaal Vol. 44 p. 6692. " "p. 501

2.

Fifty-six glazes were made, the horizontal series "being des-

ignated "by letters and the vertical series "by numbers. The mem-

bers of the group were made "by "blending the four corner glazes

according to their combining weights. The formulae and batch

?/eights of the four corners are:

Formulae Batch Vfeights

PbO Alo0, Cr () Si0 o P^* , China Gr o0„ Flint* 6 2 5 6 4 clay #7 2 °

IftA 1 1 0.1 0.02 0.5 228 25.8 3.06 18

I A 8 1 0.1 0.02 1.9 228 25.8 5.06 102

I G 1 1 0.1 0.2 0.5 228 25.8 50.6 18

: G 8 1 0.1 0.2 1.9 228 >25.8 30.6 102

The four "batches were made from materials passed through a

20 mesh sieve, ground wet for two hours and passed through a 120

mesh sieve. The glazes were applied to two sets of trial pieces.

One set consisted of 2" discs of the following composition;

Georgia Kaolin 10 parts

English China Clay #7;25 parts

English Ball Claj 15 parts

Flint 25 parts

Potash spar 25 parts

The other set were 2" discs made from Bloomingdale stoneware

clay. The trial pieces were previously "biscuit ed to cone 5. The

glazes low in flint cracked somewhat in drying hut not enough to

3.

"be serious. The trials were placed in wadded saggers and burned

in an open fire dovm draft kiln fFig, 1) , in sixteen hours, coal

"being used as fuel. When the temperature as indicated "by the

pyrometer was 880°G, cone 010 went down and the fires were drawn.

The kiln was allowed to cool slowly, the damper "being closed.

The results from this "burn were not of much value. All the glazes

were green or greenish yellow on account of the long heat treat-

ment near the finishing temperature. The glaze when in a fluid

condition attacked the body and took up SiO^, thus increasing its

acidity, under which condition Ct^O^ gives green, as is shown by

later results.

The glazes were applied to a similar set of trial pieces

and burned to cone 010 in five hours, although when the cone went

down the pyrometer showed a temperature of only 900°C. This be-

haviour of the cones is probably due to reducing conditions. The

cones fell over due to bloating at the base and were not fused.

The kiln was cooled si owls'- as before.

Owing to the fact that the glazes were not applied thickly

enough and that they were slightly underburned, it is difficult

to draw many conclusions as to their true character. The results

of the stoneware trials were discarded entirely, since the body

was too easily attacked by the glaze. On the porcelain trials

where the glaze was thin a green or yellowish green color resulted.

All the trials were green around the edge where the glaze was

thin. Also on trials where a portion of the glaze had flaked off,

a greenish yellow film was visible next to the body. Two vases

which had been dipped in glaze I A 1 came out a lemon yellow

5 •

color instead of the orange which showed on the corresponding

trials. This was due to the fact that most of the glaze had rim

off and left only a thin coating. An attempt has "been made "below

to describe the color of the glazes (Fig. 3). The texture is

shown in the accompanying photograph fl?±g. 4).

The glazes were next applied in a thicker coat to biacuited

wall tile. They were burned to a temperature of 950° in five

hours and cooled slowly as before. An open fire down draft kiln

(Fig. 2) was used, with coke as fuel. Fairly good results were

obtained from this burn and the conclusions drawn were as follows:

(See Figs. 5 and 6)

•

Increasing Cr increases redness up to .17 Cr„O r , . Beyond2 3 2 6

this point more Cr.,0 is present than can combine to form the12 3

red color, in which case the excess produces its natural green

and makes the resulting color reddish brown. This is shown in

glazes Dl, El, Fl, and Gl , all of which show increasing redness

except Gl which is a reddish brown. At 950°C from .11 to ,14

Cr.,0 seeni3 to be the hip-h limit, but .17 CroO^ with low Si0 o23 * & 3 2

produced a good dark red at 1050°C.

1.5 SiO seems to be the highest Si0 9 content at which a

good red can be produced, as the glazes higher in SiOg were green

or greenish red even when mature. The glazes containing less

than 1.3 3i ^p» wnich were green when immature, turned red when

burned 100° higher.

The best red glaze at 950o c is I D 4, with the composition

) .1 AloO-z (

PbO) (1.1 SiO) .11 Cr p ()

8B 3

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10

Group II

.

In this group the RO and Cr remained constant, the SiO2 3 «?

and Al 0~ being variables. The limits covered were:2 3

) o to 0.21 Al o 0„ (

PbO )

d{ 0.5 to 1.9 SiO o

) 0.12 Cr o 0,- (8

Fifty-six glazes were made in this group, the horizontal

series being designated by letters and the vertical series by

numbers. The members were made by blending the four corners as

in Group I. The formulae and batch weights of the four corners

are:

Formulae Batch weights

PbO Al Cr 0^ SiO Pb r,0, China Cr Flint2 3 2 3 2 8 4 clcy ^ 2 3

II A 1 1 0.12 0.5 228

II A 8 1 0.12 1.9 228

II G 1 1 0.21 0.12 0.5 228

II G 8 1 0.21 0.12 1.9 228

18.36 30

18.36 114

54.18 18.36 4.8

54.18 18.36 88.8

The glazes were prepared and applied to trial pieces

similar to those in Group I and a set of tjiese glazes was burned

with each set of Group I.

First Burn. The results obtained in this burn were un-

satisfactory for the same reasons which apply to Group I.

Second Bum. (See Figs. 7 and 8) Most of the glazes ob-

tained from this burn were underfired. In the bottom row the

glazes are all immature. In the next two rows the glazes are more

fig. V.11.

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mature. This is probably due to the slight incrpo.se of Al Og

which, when added in small amounts lowers the temperature of

fusion which is in confirmation of the findings of Purdy"'" and

Orton 2 in regard to small additions of Al^Orr.\/ 2 °

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glaze darlcer red above that point the glazes are all immature ex-

cept in the upper right hand corner, where there is a "better

balance of Al and SiO . These glazes would show some red if2 3 2

"burned higher as is shown by the next burn of tins groiip.

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and texture of the glaze. Above this point increase in SiO^ in-

creases greenness and beyond 1.3 SiO f ,practically no red shows.

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appear to be mature or nearly so. In the bottom row increase of

SiOg increases the fusion temperature of the glaze the last four

glazes being slightly underfired and tending toward green.

Glaze II A 4 is a peculiar golden brown color with many small

crystals. In the next two rows the high SiO glazes seem to be

the best. II B 8 resembles II A 4 closely the golden color being

a little more pronounced. Above .07 Al increase of Si0 o in-2 S 2

creases greenness though red crystals occur in all the glazes.

The fact that the glazes in the upper right hand corner sho?/ a

good red in spots in spite of high SiO is due to the high content

1. T. A. C. S. Vol. 4 p. 67

2 . T . A. C. 3. Vol. 5 p. 13

14.

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16

of Al which makes the glaze more basic.2 z

Increase of A1.0 above .07 darkens the color.2 3

Group III.

Pour series of glazes were prepared, using as a substitute

for part of the lead, calcium, magnesium, barium and zinc. The

best glaze obtained from the preceeding groups, viz. ID 4, was

used as the basis for substitution. The limits covered were as

follows:

Series A 1 to .5 PbO ) .1 Al 0, f 1.1 SiO o)

z(

K

to .5 GaO ) .11 Cr2

f

Series B 1 to .5 PbO ) .1 A1o

3 j

1 ' 1 310g

to .5 IlgO ) .11 Cr f

2 3

Series C 1 to .5 PbO ) .1 Al 0_ f 1.1 SiO) 2 3 ( 2

to .5 BaO ) .11 Cr f

2 3

Series D 1 to .'5 PbO ) .1 Al o0_ f 1.1 SiO o

to .5 ZnO ) .11 Cr f

2 3

The members of each series were made by blending I D 4 with

the glaze containing 0.5 equivalent of the replacing base. Each

series consisted of eleven glazes . The formulae and batch weights

of the end member s are as follows:

Molecules. Batch Weights.

PhO A1„0„£ 3

Cr.,0,, 3i02 °4 China

clay4 7

Cr„0^ 3

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j. - 1 . 11 1.1 OOQ 16.83 54

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Flint

• 5rr

• D .1 .11 1.1 114 50 25.8 16.83 54

A

PhO MgO ii2og

Cr 2 3Si0

2r°3°4 HgCGg

Chinaclay Gl

2 BFlint

.5 .5 .1 .11 1.1 114 42 25 • 8 54

B

PhO BaO A1 2°3 CrS°g Si02Pt3°4 BaC0„

o

ChinaclayJLt*

Cr2°3 Flint

.5 • .1 • J- -L l . i 98.5 25.8 16.83 54

G

BaO A1 2°3 Cr2 E

3i02 3 4

ZnOChinaclay Cr

?0„ Flint

• 5 • J L JL • JL 114 40 • 5 25.8 16.83

D

18.

The glazes were prepared in the same manner as in Groups I end II

applied tc biscuited wall tile and "burned to 950°C in seven hours.

An open fire down draft kiln (Jig. Z) was used with coke as fuel.

The kiln was cooled slowly.

The results obtained were very unsat is factory. All of the

glazes containing: more than .05 of the replacing metal crawled

very "badly. The two glazes which contained .05 CaO and .05 ZnO

respectively showed a good red color hut were no improvement over

I D 4.

f

19.

Gondii si ons.

From the results obtained the following conclusions may he

drawn*.

1. That the red color is produced when Cr 2 3functions acid,

which confirms the results of Buettner and Berge.

2. That 1.3 equivalent is the highest Si02

content at which

a good red can be produced, with .1 AlgOg constant.

3. That red may he produced above 1.5 SiO^, providing

enough A12

is present to cause the CroO^ to function acid.

4. That below 1.3 Si0 o , with .1 A1?

constant, increase

of Cr increases redness up to .2 equivalent.2 3

5. That with .12 Crr> 3

constant, increase of AlgOg

ahove

.07, darkens the red color.

6. That with .5 to 1.9 S10gt .ll Cr2 3

constant, increase of

Al up to .07. lowers the maturing temperature of the glaze.g *7.

7. That when .05 PhO is replaced by .05 CaO , BaO, MgO, or

Zno, the red color is hut slightly effected.

8. That when more than .05 CaO, BaO, I.igO or ZnO is used,

the red color is destroyed.

Ahove .05 CaO gives hrown.

Above .05 MgO gives brown.

Above .05 BaO gives brown tending toward yellow.

Above .05 ZnO gives gr-enish brown.

- * "... - *

'7* S

*-V**

A. V1