burners and torches

8/9/2019 Burners and Torches

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Burners and Torches

Torches and burners will be described as being surface-mix or pre-mix.The difference is where the mixing of the fuel gas and oxygen take

place. Remember, your torch will be burning oxygen and propane or

natural gas. Do not use torch components designed for use with air.

Pre-mix torches as a rule are capable of burning a little hotter with a

flame that can be very concentrated. Gas and oxygen are mixed in a

chamber within the torch body. This style torch is preferred when

making seals and/or when heating small concentrated areas. If youwere to be restricted to using only one torch, the pre-mix is

recommended. Premix torches have the benefit of having

interchangeable tips, allowing the user the option of changing flamecharacteristics over a broad range. A torch used quite extensively in the

industry is theNational Handtorch Type 3A Blowpipe. This relatively

inexpensive torch, with tip sizes #2,3,4,and 5 will cover most of yourneeds.

Surface-mix torches and burners are used most frequently when large

areas of glass need to be worked. Oxygen and fuel gases are mixed at

the torch tip. The flame characteristics tend to be broader and softer,with less velocity than a comparable sized flame from the pre-mix

torch. This is a good torch to use when preheating a large piece of glass

apparatus for repair, or when shaping large tubing. An excellentexample of a burner that incorporates surface-mix and pre-mix

capabilities would be the Carlisle CC Burner.

There are many other makes and models ofburners and torches

available to the glassblower. Their different flame and bodycharacteristics determine their application in the glassblowing field.

Torches (handheld) may be used as burners by simply hanging or

attaching them to some sort of fixture. This fixture may be something as

simple as a ring-stand and clamp assembly or a custom made unit thatwill hold the torch in a safe and secure manner.
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Before you start....Handle the tools you will be using. Feel

their weight and balance, how to hold them in a comfortable

manner, and how easy/hard it is to open and close valves on

your torch and burners.Always wear your safety/didymium

glasses when at the work bench.

Using the Torch

Review all safety procedures. Think out what it is that you will be

doing and know what action to take if something happens different than

expected. Read through the instruction text to prepare for the exercise.It is best to avoid surprises at this stage of instruction!

Light Up

If using the National Handtorch select the #3 tip.

1. Confirm gas delivery systems are in safe operating condition. Set

regulators at 5 psi gas and 10 psi oxygen.

2. Open gas valve full turn to purge air from the line and then quickly

close valve.

3. Repeat step 2 with the oxygen.
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4. Open gas valve approximately 1/4 turn - ignite gas with flint lighter.

5. The torch is lit! Adjust the gas valve to produce a flame about 3/4"

long. This is known as a pilot flame. You may leave the torch flame atthis position when not in use - but always attended.

Tip: If you experience difficulty in immediately igniting the gasbeware of excessive gas buildup. Shut the gas valve off and wait a

few minutes to allow the gas to dissipate. Attempt to light the torch

again using a different setting on the gas valve.

Adjusting Flame Size

1. Gas first - open valve to create a flame length about 6" long (about

the length of your hand). The flame should be still attached to the torch

tip. If there is a space greater than 1/8" between the flame and torch tip

adjust (close) the gas valve until the flame "re-attaches" to the tip.2. Slowly open the oxygen valve. Observe how the flame changes in

shape, velocity and heating characteristics.

3. Practice flame control by changing the settings on the gas and oxygenvalves. Make the smallest flame possible, using an inch long flame as a

target. Now attempt to create the largest flame possible. Try different

tip sizes to observe the flame size range each produces.

Tip: Take the time to become comfortable handling your torch

now. With practice, creating the various flames necessary to

produce sound glassblowing seals will become second nature.

Relative Flame Size Guide


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Bangs, Pops and other Surprises

1. If the torch should suddenly bang orpop as a result of improper

gas/oxygen mixing, immediately close the gas and oxygen valves at the

torch. Re-open the oxygen valve to flush out the mixing chamber in thetorch body, extinguishing any flame that may have flashed back into the

chamber. This action only takes about 5 seconds. Close the oxygen

valve. The torch is now ready to re-light.2. If the flame extinguishes itself (improper gas/oxygen mix) and thereis no pop or bang, just close the gas and oxygen valve. Re-light.

3. Flame appears where its not supposed to! Close the supply line

valves closest to the torch. Re-check all connections, valves and fittings.

Determine the Correct Flame Size

Flame sizes are determined by what you are attempting to do with the

glass. Only glass that has been heated to the working point range will

be soft enough for you to form into the shapes or seals desired. Heatingan area of glass 10 mm in diameter means only 10 mm of glass will be

hot enough to to shape or form. Logically it would follow you do not

heat an area 30 mm in diameter to seal on a tube that is only 10 mmOD. Match the area of hot glass to the size of the seal.

Flame intensity is a factor in determining how quickly the glass reaches

working point temperatures. Experience will guide you in choosing the


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proper flame intensity and flame size to apply to the different types of

seals. Each person will develop their own style and technique in using

the torch. The information presented here should serve as a startingpoint.

Shutting Down the Gas Delivery System.

To shut down and relieve all positive pressure from the gas delivery

system:

1. Close valve at the gas source.

2. Open valves at the torch and burn off released gas.

3. Back off pressure adjusting screw at the regulator(s).

Cutting Glass

Glass tubing and rod come in four (4) foot lengths and metric diameters.

Four feet of tubing is rather awkward to handle in the flame so we need

to cut it down to a manageable size. Select tubing of 10 mm OD andplace on a flat surface. Mark the glass into 16 inch lengths.

Option #1

1. Create a scratch on the glass wall surface by drawing the corner of a

file ortungsten carbide knifeperpendicularly across the tube.

Tip: Do this step once creating a scratch approximately 1/8 inch

long. Do not saw the glass. Sawing the glass will not make the process

of breaking the glass any easier. It is not necessary to make a longscratch. A short, single sharp scratch is more likely to produce a clean

even edge.
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2. Pick up the glass tube and wet (water, saliva) the scratch with yourfinger. Turn the scratch away from your body.

3. Place your thumbs on the glass tube. The scratch should be locatedbetween the thumbs but on theopposite side of the tube.

4. Push your thumbs away from you. The glass tube should break

cleanly at the scratch.

Option 2.

1. Hold glass tubing in one hand

2. Hold tungsten carbide knife in vertical position with other hand.Place glass tubing between your thumb and knife, hold firmly -

horizontal and close to your body for support and stability.

3. Twist hand with knife - creating scratch.

4. Break tubing as in Option #1- step 4.

Option 3.

This option is useful on large tubing or when repairing vacuum lines orapparatus. This method should be tried after you have had some

experience handling the torch.

1. Scratch tubing with file or carbide knife.


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2. Wet scratch.

3. Heat the end of a 6 mm rod red hot - quickly place the end of the hot

rod onto the wet scratch - be sure the scratch line extends beyond thecontact area of the hot rod.

Tip: If done correctly you will observe a crack forming at andextending from the scratch. If the crack does not travel completely

around the circumference: Tap the cracklightly. This action may chase

the crack around the tube. Or, reheat the glass rod and reapply to thecrack. Again, be sure the rod does not extend beyond the endof the

crack.

Option 4. Access to a glass saw or cut-off wheel can make this process easier for some.

Rotation

This is a difficult skill to develop and the lesson plan will minimize its

use. However, it is a valuable and worthwhile skill to acquire and your

glass products will reflect your proficiency in rotating glass tubing.

1. Select a glass tube from the previous lesson.

2. Grasp the tubing with both hands and hold horizontally.

3. Rotate glass in a clockwise (top away from you) direction.

Tip: Hold hands palm down. Thumb and pointer finger will serve

as the "motors" turning the glass tubing. Remaining fingers squeeze the

tubing against your palm. These fingers serve as a sleeve bearing,

aiding in the support and stability of the glass tube while rotating.
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To self-test your mastery of rotation skills, select two pieces of glasstubing 10 mm OD and approximately 8 inches in length. Place one

piece of tubing in each hand and practice rotation, aligning each tube to

the same imaginary centerline. Synchronize rotation and observe for

consistent alignment.

Practice rotation with a blowhose assembly attached to one tube.

Proficient rotation ability takes many hours/days of practice to acquire.

It will become apparent as you develop your glassblowing talent the

importance of developing this skill.

Fire Polishingand Annealing

Fire polishing the ends of glass tubing and rod will seal small cracks inthe end wall, reducing the chance of fractures originating from thissource. Fire polishing ends will also reduce cuts and abrasions to you or

anything (corks, latex tubing, etc.) coming in contact with the glass end.

1. Cut 10 mm tubing into 16 inch lengths (or use tubing from previous

lesson).

2. Light and adjust torch flame (sharp/soft).

3. Fire polish by rotating the glass tube end in the flame.

A good fire polish has a smooth finish and the ID and OD of the glass

tube remains unchanged.
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Tip: Hold the glass tube in a declining or horizontal position

with the tube end angled away from you. This will prevent the flamefrom traveling up the tube and out the far end, possibly resulting in a

burn.

Annealing

Whenever glass has been altered or shaped by exposure to a torch

flame, you can be sure that stresses have been introduced. Theglassware you make can have some of the stresses reduced by hand

annealing. Stresses are not visible to the naked eye, so you have to use a

little imagination in performing this step. If you have access to a

polariscope, check out your seals before and after annealing. The more

complicated the seal, the more likely to have stresses harmful to thefinal product and you.

Use a soft, bushy annealing flame to "brush" away the stress areas

located in and around the area of your fire polish and other seals youwill learn to make. Think of your flame as an artists paint brush. The

strain (paint) needs to blend into the surrounding glass smoothly, with

no jagged edges.
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Test Tubes

Test tubes are relatively easy to make, frequently used, and give you an

opportunity to practice rotation and fire polishing skills. This exercisewill introduce you to the process of blowing into the glass, forming and

shaping the tube end.

1. Select 10 to 18 mm OD tubing - 16 inch lengths with fire polishedends.

2. Light torch and adjust flame to match tubing diameter.

3. Grasp tubing with both hands - rotate.

4. Place rotating tube in flame at the half-way (8") point.

5. When the tube softens (cooked noodle au dente?) and constricts tohalf its original diameter, remove from the flame, do not stop rotating,

and slowly pull about 6" apart.

6. Place tubing back into flame and burn off into two equal lengths.

This exercise is known aspulling points. Place the points on the hot

glass rest to cool.


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Tip: Roll the glass point (after cooling) on a flat surface. If yourrotation is good the glass tube and "point" will be centered.......no

wobble!

7. Adjust your flame to a sharp/intense profile.

8. Place the shoulder of the glass point into the flame at an angle -rotating at all times - and pull off the excess glass, leaving a semi-

rounded bottom.

9. Attach theblowhose assembly to the glass tube.

10. Reheat the tube bottom to the working point temperature and blow

(little puffs), shaping the tube bottom.

11. Anneal

Tip: This is a good time to practice the process of blowing glass.Try different flame and blow pressure combinations to see how the

glass responds. Position the glass tube in different regions or angles ofthe flame. Glassblowers will use combinations of heat, flame size andangle, gravity and pressure in shaping glass. With experience you will

learn how much or hard to blow air, when to let gravity work for you,

and even when to inhale to produce that certain look or shape.
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In almost all cases you should strive to maintain an even wall thickness

throughout your glass project. If the glass tube is not rotated or heated

evenly the glass wall may become lop-sided, thick on one side and thin

on the other. It will be difficult to control the glass being worked if thedifference in wall thickness is too great. The uneven wall thickness will

not heat to the working temperature uniformly, resulting in hot spots

(thin wall) that blow out and cold spots (heavy wall) that do not move.Even wall thickness will help you produce structurally sound glass

apparatus.

The importance of good rotation should now be apparent.

Butt Seals

Butt Sealing is the process of joining two sections of glass tubing

together - end to end. This exercise demonstrates the joining of two

similar size tubes together. A variation of this seal would be the

joining of two dissimilar size tubes. Two options are offered - onerequires good rotational skills.

Option # 1

1. Cut tubing into 8" - 12" lengths, fire polish ends.

2. Attach blowhose assembly to one tube.

3. Seal second tube with a cork or use a test tube bottom from the

previous lesson.

4. Light torch and adjust flame.

5. Rotate ends of glass tubing (as if fire polishing) in flame.


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6. When tube ends are red hot remove from flame, stop rotating, push

tubes together making contact all around.

7. Back to the torch, keep the flame concentrated directly on the seal,

rotate and blow, maintaining ID and OD.

8. Anneal

Tip: When at Step 6 (pushing or "butting" the tubes together

making a seal), some glassblowers will pull the tubes slightly apartimmediately after butting them together. The reasoning is as the tubes

are butted together there will be a thickening of the glass wall at the

point of contact. By slightly pulling the tubes apart the glass walls willcome back to their original thickness, making it easier to work out the

seal. Do not pull too hard, however. You want to avoid creating a thin

spot or section in the tube, producing a potentially weak seal.

Option # 2

This option does not require rotation. It does require the glassblower tohold and manipulate the torch around the glass tube that is held in a

standard laboratory ring stand.

1. Clamp tube #1 vertically in a ring stand. Tube end about chin highwith blow hose attached.


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2. Hold in one hand the torch adjusted to a sharp flame. A sealed tube

(#2) is held in the other hand.

3. Sweep flame back and forth across the end of tube #1, concentratingon the back half of the tube.

4. Tube #2 is simultaneously held directly above tube #1 at a slight

angle. This tube will also be heated as in step 3.5. Bring tube #2 down contacting the back of tube #1, continue to

sweep flame back and forth across the tube ends.

6. Continue to bring tube #2 down onto #1 making complete contact

around the circumference. With practice steps 5 and 6 are completed ina quick smooth continuous motion.

7. Using a small sharp flame, work out the seal by heating small

sections of the seal at a time.

8. Anneal

Tip: Heating large areas of of glass using this technique may give

you control problems at step #6. Concentrating your heat onapproximately 20 % of the tube diameter at a time should give you thebest results.

burners and torches

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