Brad Shute's Wicked Good

Semi - Technical
How to do Stuff

A little technical info about how to do different glass related stuff.

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* Updated December 13, 2000 *

Okay, I admit it, this really shouldn't be called my how to do stuff page. I didn't write this advice. I borrowed it from the Arrow Springs website (with their permission) and made some slight additions. So - call me lazy for not writing it myself - I worked on my leaky roof instead.

This advice was written primarily for glass bead makers, but is applicable to other kinds of flameworking (lampworking) too. For those who don't know, Arrow Springs sells flameworking equipment and supplies. They are one of the best suppliers out there, and their catalog is accessible online. Contact information for them is at the bottom of this page.

If this advice helps you, thank them, not me. After all, they wrote it. I simply made some slight modifications to the format for ease of use, added a small amount based on personal experience, and did some minor editing for clarity. As I have time, I may edit/add a little more and include some topics of my own. To view the original version, go to the Arrow Springs website at:

Index of Subjects

IMPORTANT! Read This Before Installing Pressure Regulators

Improper installation and use of pressure regulators can be dangerous and may cause damage to the regulators and/or the person using them!

Before connecting pressure regulators to their respective cylinders, position the cylinders in a safe location away from flame and out of walk ways. The fuel cylinder (probably propane) must be in its upright position sitting on its intended bottom. Fuel gas is usually pressurized to a liquid. The cylinder valve must be positioned above the liquid in the gas for the pressure regulator to work properly. The oxygen cylinder can be in any position. It is usually best to stand it up. Before removing any safety cap, secure the cylinders to a wall or the work bench if it is stable enough to give proper support. [In many places it is legally required (and also a VERY good idea) to have the oxygen cylinder securely chained - whether to a tank cart, the wall, or some other immovable object - to keep it from being accidentally knocked over. NEVER move an oxygen tank - full or empty - without the protective cap over the cylinder valve. If a full tank slips and falls without the cap, the valve can be damaged or even knocked off, which can actually kill you or someone else due to the released oxygen pressure turning the tank into a missile or lethal spinning top. It HAS happened. If the tank is empty and the valve gets damaged without anyone noticing, it makes it just as dangerous for the poor guy refilling it. There's no need to be paranoid about this, just exercise some sense and caution. - Brad]

Remove the caps from the cylinders and connect the pressure regulators. Connect the torch to the output side of the pressure regulators with proper hoses. The standard color coding of oxygen lines is green and fuel gas is red or orange. Propane must only be used with a Grade T hose. Regular Grade R hose, which is fine for acetylene, will eventually rot with propane. Be sure that there is no oil, grease or debris in or around the cylinder valves, hoses or on any part of the pressure regulators. Grease and oil are explosive in the presence of pure oxygen. Debris on the fittings will not allow for a proper air tight seal. The thread pattern on the oxygen cylinder is right handed (tightens clockwise). The thread pattern on the fuel cylinder is left handed (tightens counter-clockwise). Left handed threads are indicated by a notch around the fastening nut on the pressure regulator and the hose. The fittings on both pressure regulators and the hoses are flair fittings and only require moderate tightening. It is not necessary to use a thread sealer.

There is only one way to turn on and off pressure to the torch without causing damage to the pressure regulators:

Before opening the cylinder valves it is important that the pressure adjusting knobs are backed off to a zero pressure delivery. This is done by turning the knob counter clockwise until the resistance of the knob turning becomes easy. If the knob comes off the regulator it is OK. Just screw it back on one full turn. If the knob is not backed off when the cylinder valve is opened, the fast inrush of gas will damage the diaphragm inside the pressure regulator. Check that all torches connected to the regulators are off. Before opening the cylinder valve stand next to (not in front of) the pressue gauges, positioning the cylinder valve between you and the regulator. If the pressure regulator is damaged it may blow off the cylinder when the cylinder valve is opened. Standing behind the cylinder valve is the safest location. The oxygen cylinder is under high pressure and uses a special double seat valve. The valve only seats with an air tight connection when it is fully closed or fully open. Any position in-between will slowly leak oxygen from around the valve stem. Open the oxygen cylinder valve all the way. The fuel cylinder is usually under much less pressure and uses a different kind of valve. Open this valve only one half to one turn. This makes it faster and easier to turn off the cylinder in emergency situations.

Turn the pressure adjusting knob clockwise to allow gas to pass through the pressure regulator. The more the knob is turned the greater the delivery pressure will be. The pressure gauge closest to the cylinder valve indicates the cylinder pressure. The other pressure gauge indicates delivery pressure. To reduce delivery pressure, turn the adjusting knob counter-clockwise. The delivery pressure gauge will not indicate a lower pressure until the pressure is relieved on the output side of the pressure regulator. You can do this by lighting the torch. After making any connections, and before turning on the torch, you should check for leaks. This is done by applying soapy water to the connections with a spray bottle. Any leaks will show up as a series of small bubbles.

To shut down the system, close the cylinder valves, burn off the pressurized gas in both gas lines by lighting the touch. As the flame goes out turn off the torch. Back off the pressure adjusting knobs as described earlier.

The most commonly used pressures are 8 to 10 lbs. for the oxygen and 4 to 5 lbs. for the fuel gas.

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Installing and Using the Minor Bench Burner

Only use safety approved Grade T hoses to connect any torch to its oxygen and fuel supply. [I personally use 1/4 inch i.d./1/2 inch o.d. surgical rubber tubing. This is much more flexible than standard rubber welding tubing and allows one to move the torch around at will as one works. It is not recommended for beginners as it is far less resistant to abuse or accident (read - dangerous!) and must be checked for leaks at regular intervals as it rots and cracks eventually. In fact, I probably shouldn't have even mentioned it... Brad] Before installing the hoses, cut the green oxygen hose 1/2" to 3/4" shorter than the red fuel hose. This forces the hoses to bend down towards the ground instead of sticking straight out towards you. Secure the hoses to the torch with hose clamps and secure the torch to the workbench so the heavy hoses don't pull it into your lap while you are working. The RED fuel gas hose leads to the RED KNOB on the torch. The GREEN oxygen gas hose leads to the SILVER KNOB. If the hoses are connected backwards, the torch will not work properly. Tighten the clamps only enough to slightly bulge the hose, but not cut into it. If the hose if difficult to push over the torches hose barb fittings, wet the fittings with water only. NEVER use grease or oil anywhere near oxygen. Grease and oil are explosive in the presence of oxygen. (Sound familiar?)

The minor burner can be used with propane, hydrogen, butane or natural gases only. Never use acetylene.

Connect hoses to properly installed regulators. See our instruction sheet for proper regulator installation. The most commonly used pressures are 8 to 10 lb.. for the oxygen and 4 to 5 lb.. for the fuel gas.

Typical oxygen consumption for the minor burner is 10 standard cubic feet (scf) per hour. Propane is approximately 1 gallon per 500 scf of oxygen.

To adjust a minor burner flame properly: Light the torch with only the fuel gas on and then add oxygen until the flame has a small inner blue flame of about 3/8" long surrounded by the larger yellow/orange flame. For a normally used neutral flame, the very tip of the blue flame should be ever so slightly fuzzy. If the tip of the blue flame is very fuzzy, you have a reduction flame and you will find that some colors will reduce to grays or some other unexpected color. To correct this, add oxygen or reduce the amount of propane. If the tip of the blue flame is very sharp and well defined, you have an oxidation flame. Add propane or reduce the amount of oxygen.

If you find that you need more heat, adjust the gases to make the flame proportionately larger or try working in the flame closer to the torch where the flame is hotter.

If you find that the glass burns or bubbles or has "scum" on it (scum is actually micro bubbles), then you are getting the glass too hot. This can be corrected by one or all of the following: Rotate the glass more to better distribute the heat throughout the glass, try working in the flame further from the torch where it is cooler or adjust the gases to make the flame proportionately smaller.

A reduction flame is cooler than a neutral flame, although it may feel hotter to you, and has a large bushy look to it. It is also very dirty and may deposit soot on the glass as well as reduce it.

An oxidation flame is also cooler than a neutral flame and the overall flame becomes very short and needle like. This type of flame is ideal for working with stringers, because it has a jacket of cool, unburned oxygen around it that insulates the stringer from the heat of the actual flame thereby giving you better control. A neutral or reduction flame tends to make the stringer soft some distance from the flame quickly and you will soon lose control of it.

(These instructions were written by Arrow Springs, not Nortel Machinery who manufactures the minor burner.)

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The following is an excerpt from the Arrow Springs annealer manuals...

What Is Annealing? Why Is It Important? and How To Do It.

Annealing is the process of first making the entire bead uniformly hot enough to remove all stress within the bead and then cooling it down slow enough so as to not allow too much stress to build back up.

Stresses are caused when the bead is too rapidly cooled. As the bead cools, the outside will always cool faster than the inside. As glass cools it contracts. If the outside of the bead cools much faster than the inside, the outside glass contracts faster than the inside glass. This variance in contraction is what causes stress in glass. Too much stress and the glass breaks.

The way to remove stress or prevent it is by heating the glass in an oven (annealer or kiln) hot enough to cause the glass to flow. If you heat the glass until it is molten, there will be no stress in it at all, but its shape changes immediately. However, if you heat it to the proper temperature, these stresses can be relieved without distorting the bead. You do this by heating the beads to the proper annealing point temperature and holding that temperature, called soaking. This allows the glass to "flow" and release its stresses, but still hold its shape. Ideally, you would make the bead, flame anneal it and then immediately place it within an oven idling at or near the annealing temperature. Alternatively, you can make the bead, flame anneal it, store it in vermiculite or a fiber blanket and then, when it has cooled enough to handle, place it in an oven and take it up slowly (to not thermal shock it) in temperature to the annealing temperature to soak.

Once the glass has soaked, to remove stress, it is time to cool it. This will put stress back into the beads but, at an amount that you can control. The faster glass cools, the more stress is locked into it. Thicker glass will obtain more stress than thinner glass that is cooled at the same rate. As heat is released from the surface of the glass, the heat from the inside then travels to the surface to escape. Because glass has a relatively low thermal conductivity, this process is rather inefficient and happens slowly. To compensate for this, the glass must be cooled slow enough so as not to let too much stress develop. The thicker the glass, the slower you must cool it.

It is technically impossible to eliminate all stress from glass (unless, of course, it is hot enough to flow) because, no matter how slow you cool it, the glass always cools from the outside. The inside is always somewhat hotter. It is this temperature gradient that causes stress. The whole premise of annealing is to minimize this stress. A certain amount of stress is acceptable. Some glass manufactures, such as vessel makers, actually design some stress into their annealing schedules. An overly annealed piece can sometimes break easier. Slight amounts of stress can actually make some shapes stronger by "binding" their shape. For the purposes of annealing beads, especially spherical shapes, don't worry about over annealing, only about under annealing.

For Moretti glass, the annealing point temperature is between 920 and 968° F. In this temperature range, the glass is "flowing" on a molecular level. Its movement is so slow that it is not apparent to us within any reasonable length of time. If you soak the beads at the upper temperature range, the soak time is less than at the lower temperature range. However, you risk the possibility of accidentally overheating them to the point of distorting them. We recommend starting the annealing process closer to the lower temperature range at 940° F and holding that temperature for a 20 to 30 minute soak time.

At the end of the soak time, you begin the cooling period. For smaller beads, all you need do is turn off the oven. If the oven has been on for a while, the brick walls will have absorbed a lot of heat. This stored heat keeps the firing chamber from cooling very fast. As mentioned above, the faster the glass cools, the more stress is developed in it. If you have made larger beads, you will want to cool them down at a slower rate. 5 to 10° F per minute (300 to 600° F per hour). This can be accomplished by several different ways, depending upon how your oven is controlled.

If your oven is controlled by an infinite switch, try selecting a setting that is lower than the setting used to hold the temperature steady while soaking the glass. This causes the oven to be starved for power. The walls will dissipate more heat than the heating elements can add heat. The lower the setting, the faster the oven will cool. As the oven gets cooler, the rate at which the temperature decreases slows and the temperature within the firing chamber will eventually stabilize. You may have to decrease the setting again to have the oven drop in temperature low enough. When the oven is at the desired temperature, turn it off. Using this procedure will require a few test firings to become comfortable with it. The easiest method to learn its characteristics, is to pick a setting and observe the pyrometer. Perhaps, note the amount of temperature change over a several minute period.

If your oven is controlled by a temperature controller, the procedure is different. If the controller has a ramping feature or utilizes a percentage of power function, you can control the cooling rate quite effectively. To do this, follow the instructions for the particular controller you have.

When glass heats up it expands. Different glasses expand at different rates. The amount of expansion is measured over a specific temperature range and is referred to as the glass' C.O.E. or Coefficient Of Expansion. Glass will continue to expand until it reaches what is called the strain point. For glasses to be compatible with each other their C.O.E.'s must be close to each other and their melting points need to be fairly close as well. If you have two glass that expand while heating and contract while cooling at the same rate, but their melting temperatures are quite different, those two glasses may not be compatible. One glass will be firm while the other is soft. Their movement will be out of sync.

As explained earlier, glass develops stress in itself through the cooling process. The cooling of glass is most important between the annealing point and the strain point temperatures. Stress that develops in the glass between the annealing point and the strain point is permanent. Even after the glass cools to room temperature, those stresses will remain within the glass indefinitely. Any stress that develops below the strain point temperature in the glass through the cooling process is only temporary. Once the glass has stabilized to room temperature, those stresses will disappear. Because of this fact, you can accelerate the cooling time below the strain point temperature and not worry about this strain causing the glass to break at some time in the future. However, too fast a cooling rate can still break the glass from thermal shock while in the oven.

Using this information, you can get your beads out of the oven faster. When the temperature in the oven drops several hundred degrees below the strain point, you can slightly crack open the door or lid to speed up cooling. If your beads come out broken, it is probably from using incompatible glass or not properly flame annealing the bead before placing it into the annealer. The strain point for Moretti glass is 840° F.

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Using Sludge Plus Mandrel Release

Sludge Plus gives superior holding strength to the tugging and twisting rigors of even the most aggressive beadmaker, yet the bead easily twists off when it cools. Sludge Plus is the best mandrel release available and we back it with an unconditional, money back guarantee. Sludge Plus comes premixed, however the water in it will separate with time and it needs to be mixed back in. Also, the water will evaporate when the lid is off for an extended period of time leaving it too thick. Here are some hints and techniques to obtain optimal performance.

If you dip the mandrel into Sludge Plus and find that it is uneven, lumpy and patchy, it is too dry. Add a small amount of water and stir or shake well. A mandrel that is coated with this type of mixture may cause the bead to stick and the release to flake off. If you dip the mandrel into Sludge Plus and find that it is coated very thinly and is drippy, then it is too wet. Leave the lid off and allow the mixture to dry a little, then stir or shake well. Double dipping the mandrel to apply a thicker coating is not recommended to compensate for a thin mixture because it is not as dense as it should be. Even though double dipping puts a thicker coating on the mandrel, it does not make the mixture denser. Low density mandrel release is not as strong and you will find that large beads may spin loose from the mandrel. Also, a thin coating doesn't give much clearance between the bead and mandrel which makes it harder to remove the bead from the mandrel if the mandrel is even slightly bent.

To coat the mandrel evenly we recommend the following procedure: Hold the end of the mandrel loosely between your finger and thumb. Quickly dip the mandrel into the release and then quickly pull it out. Holding the mandrel this way insures that it will go straight in and straight out and make a round coating. If the mandrel is withdrawn at an angle, the coating may have a ridge down its length. The action of dipping the mandrel quickly causes the release to coat thicker by forcing some of the water to remain behind. To coat the mandrel thicker, quickly dip the mandrel in and out several times. The more you repeat, the thicker the coating.

Very important!

Heat the mandrel until red hot for one full second in the area where the bead will be. The magic about Sludge Plus is that it holds beads when they are hot and releases them when they are cool. This will only happen if the area of mandrel release holding the bead has been heated until red hot before glass was applied to it. If not you will find that removing the bead will be difficult. If a bead ever sticks to the mandrel, you most likely did not get the coating hot enough. When the bead cools, the coating will lose its strength permanently. For this reason, apply glass to the mandrel while the coating is still very hot. It need not be red hot, but almost. If the bead ever spins off while you are making it, you probably let the mandrel get too cool before applying glass to it. Once glass is on the mandrel, proper beadmaking techniques will assure that the glass will hold enough heat to keep the coating hot.

After coating the mandrel, let air dry. If your in a hurry, Sludge Plus can be slowly dried in the back part of the flame.

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Making Core-Formed Glass Vessels

Glass core vessels were one of the first glass items ever made, perhaps preceded only by glass beads, small glass sculpture and imitation stones. Originally glass core vessels were formed over a mixture of sand and clay that was sometimes supported by a metal mandrel. Today the process is similar, except with today's modern materials available to us we can modernize the technique while still keeping the integrity of the process developed thousands of years ago by glass pioneers. This method can be used to not only make vessels, but also large hollow beads.

Take 00 or 000 steel wool and pull it apart to make thin layers. Wrap it around a stainless steel mandrel. An 1/8" or larger mandrel is better than the smaller sizes because the larger size mandrel holds the steel wool better and helps prevent it from spinning loose while working the hot glass. Wrap the steel wool tightly at first, so it won't slip, and then a little looser so as to be able to make the wrapping go into the shape you want. The steel wool wrap can be placed near the end of the mandrel to make an item with a hole at each end like a bead, or at the very tip and even past the tip to make a vessel.

When you are satisfied with the shape, use a small brush to cover it with Sludge Plus mandrel release. Apply several coats, if necessary, allowing them to naturally dry between applications. The final thickness of the coating should be at least 1/16". Make sure that the mandrel release covers all of the steel wool, not just where the glass will be applied. A full coverage coating adds a lot of strength to the steel wool and insulates the steel wool from direct contact with the flame. Be certain that the mandrel release covers the steel wool and continues onto the mandrel. This helps in keeping the mandrel from spinning free. You can smooth out the surface with your finger before the mandrel release dries or you can wait until it dries, wet your finger and smooth the surface. The second method gives you more control because it only affects the surface leaving the under coat to hold the shape.

Once the mandrel release has fully air dried, introduce it to the flame to heat it up similar as when making a regular wound bead, but don't let it get too hot or the extra thick coating of mandrel release will crack and the steel wool will burn up. If a little cracking happens or if a little steel wool burns you should have no problem, but the core will be a little more delicate.

Finally, apply the glass where you want it. Work it as you would if making a regular wound bead or sculptured glass. Be very careful to not pull or push too hard or the core will slip from the mandrel. If you use an opaque glass to cover the mandrel release, the coating's surface imperfections won't show and you don't have to be so fastidious about cleaning out the inside.

After annealing, remove the steel wool by picking it out. The mandrel release is harder to remove. It can be removed by scraping or you can use a moto tool with a diamond burr.

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Using Reduction Frit

Use reduction frits to create a metallic luster similar to a raku like effect. To use, place frit on a marvering pad. Heat the bead enough to pick up the frit and melt it in. Apply frit very thinly to the surface of the bead for best compatibility. Adjust the torch to a strong reduction flame. When you re-heat the bead, the reduction flame causes the metallic oxides to come to the surface. Small frit covers the bead with a continuous luster. Large frit makes a broken or patchy pattern.

HINTS: After you have applied the frit to the bead, form the bead to its final shape. Allow the bead to harden but, still remain hot. Quickly heat the surface of the bead until molten. Do not allow the inside of the bead to become molten or the bead will probably lose its shape during the following steps. Quickly change the flame to a strong reduction flame (excessive fuel gas, lacking in oxygen) and rotate the bead in it. The reduction frit should start changing within two seconds and continue to change for up to ten seconds. You must flame anneal the bead in this reduction flame. If you change the flame to a neutral or oxidation flame, the metallic raku effect will disappear and you will have to repeat the process.

NOTE: When you change to a reduction flame, the flame will probably increase in length. Be sure nothing is in its way. Also, the flame will feel hotter to you but, it is actually a colder flame to the bead. The colder flame eventually stops the process because, the glass will cool and no longer be molten. The metallic oxides will not be able to get to the surface. This is why you must quickly change the flame to a reduction flame and immediately put the bead in it. Practice is required. Timing is very important.

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The vast majority of the advice on this page was written by Arrow Springs:

Manufacturer and Supplier to the Flameworking Industry

Arrow Springs
331 #2 Industrial Drive
Placerville, CA 95667
Phone: 1-800-899-0689 / 530-344-9219
Fax: 530-344-9216

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