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  • Advanced Torch Paradigms

    this is an article for Glassline I wrote ( July 2011). i highly recommend a subscription so you can go online and read all the back issues: there's tons of tips and great articles. when you have one, you can then see the pictures i refer to, which will then make much more sense. this is rather long- you may want to actually print this out and take notes on it, as it usually takes a few reads for it to really sink in. seriously try this, it'll change your glassblowing life.


    Advanced Torch Paradigms: Using compressed air and inline regulators to drastically improve your torchís range, the quality of your work, and your understanding of the whole process.

    Congratulations to Jim Thingwold for 25 years of Glassline! From a newsletter to a full fledged magazine and online forum, youíve helped this young scientific material process grow into a real American Art movement! For this special issue Iíd like to share with you what I think is the most important aspect in fully understanding the process of flameworked colored borosilicate glass; the ultimate control over your heat base and flame chemistry. When you truly understand how and why things are working, itís much easier to create whatís in your head and push your work to the next level. This true understanding can only come from a little education, exploration, and the right set up.
    While thereís often more than one way to do many things in glass, there is usually only one perfect way to do it. By having inline regulators within easy reach, and by manifolding a little compressed air into your fuel line, youíll have a flameworking station that will help you find the perfect heat, not limit your options by running your torch at the lowest common denominator. When itís easier to control your torch, youíre more apt to experiment with just the right flame for the job. When you have just the right flame, your heat base improves and youíll be amazed at how much easier it is to do just about everything.
    As you learn, you will l become less restricted by your equipment, your control and understanding over the entire process will drastically improve, and so will your work! Everything comes full circle, and itís worth the investment and time exploring to get there. In the mean time, some of the theories Iíll explain are a bit advanced. Theyíre best suited for large, multiple staged torches, and for those who are in good control of them. Adding air to your flame or drastically changing pressures can complicate things, or just make things worse if you donít do it correctly. But itís not rocket science, so give it a shot. I can guarantee it will at least change the way you see your flames, and if you follow my advice, your torch will run better on an inline set up, even if you donít try radically changing things.
    Definitions of a few torch basics and generalizations are useful for a better understanding of the different types or brands of torches and how they compare, which leads to a basic understanding of the variables affect your flame. The first generalization is what I call the torch spectrum: Torches generally fall in either the soft or thrusting category, but can usually do a bit of both. Remember that a center fire is really a small torch within a larger one, so itís useful to think of them separately. For example, a Carlisle CC usually has a premix center fire (thrusting) within a larger surface mix outer fire (soft). This contrasting set up gives a nice range to the torch. Both are independently controlled stages or torches, and can be fed different pressures. Unfortunately thereís no such thing as a torch that can do it all perfectly, and each has something special it can do best.
    On the far end of the soft side of the spectrum are the Herbert Arnold Zenit torches, like the 40mm 50mm or 65mm models. These torches are referred to large orifice, low pressure torches (referring to the low fuel pressure). Since they donít really have a propane knob, but rather a hand wheel that sequentially opens up rings on the torch, controlling the fuel amount is done by adjusting the very low propane pressure with an inline regulator, or by cutting the gas flow with a cut off valve on the fuel inlet. This set up has the advantage of being able to control the atmosphere of the whole torch at once (no matter how many rings are open, or how big the flame is).
    This type of torch also has a flame that is different than most torches because it travels so slowly. This flame envelops the glass and soaks in quite evenly and is ideal for hollow work. Because the flame is so gentle and enveloping, it is also ideal for fuming and assembling large parts. An even heat base equals more forgiving welds and stronger glass. Colors that have boiling problems are a cinch to work on this type of flame, as are colors that are prone to devitrification. Conversely, working thick solid glass or doing large prep work with this type of flame tends to go VERY slowly. It takes something with some thrust to work thick glass efficiently. Also, itís difficult to get a true oxidizing soft flame. Even with the fuel cut to thin the flame, oxidation comes not only from the flameís mix, but itís energy. Soft oxidizing flames are cold, and lack the energy to undo reduction: That is, theyíre ďnot very oxidizing.Ē You need some thrust to do that!
    On the opposite end of the spectrum (in the thrusting, or high velocity range) are premix torches and triple mix (Glass Torch Technologies/GTT) torches. These torches are characterized by higher fuel pressures and smaller orifices (ports) and have very penetrating hot feeling flames. One of the best advantages of this type of flame is that itís easiest to control the flame chemistry: Oxydizing flames are a cinch to dial in, just add more oxygen! Colors that prefer a hot surface to keep the ďHazeĒ burnt off do well with a thrusting flame. And when it comes to working thick glass, pound for pound thereís no better torch than a GTT.
    On the other hand, high velocity flames heat like a laser. When working on thinner glass, this is far from ideal. Hot spots lead to off center bubbles when making stemware and arenít as good when youíre trying to be gentle to the surface. These harsh flames tend to heat the surface very quickly, while the core might still be cold. This can create a situation where your heat base is uneven or where devitrification likes to form. Overheating or over working the surface can also cause or create flux burn out, leaving your glass less shiny. Unfortunately GTTís donít run slow flames very well. They need the gasses running through them to cool their delicately machined ports or they quickly deteriorate. There is a whole range of flames that these torches cannot safely run without the addition of compressed air. It is possible to add more fuel to soften the flame, but you sacrifice the neutral mix of the flame. Thatís fine for clear, but terrible for some colors and powders.
    While these are just generalizations, they are fundamentally true. Iím not saying you canít blow thin bubbles or work softly on a GTT, or that you canít get a Herbert Arnold up and raging to work thick glass. Iím simply making the case that by nature their different designs lead them to do certain things better than others. To realize each torchís full range, it helps to understand what factor makes each especially suitable for certain tasks so you can best imitate it on the other. You can use inline regulator pressure changes and compressed air to maximize the range of each style of torch and minimize its shortcomings. If you donít have either of these torches, the principles are still the same, just not the specifics. Iím referring to these two brands simply because they represent the ends of the spectrum.
    For GTTís, you can run softer flames by slowing them down and manifolding in some compressed air into the fuel line. Simply take a Y splitter with stop-cock valves, flip it around backward, and manifold the fuel line and the air lines together. You just

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