Q: Is there a trick to lighting an oxygen-acetylene torch without getting that black soot all over the place? I’ve got a Little Torch and it either makes a big mess or won’t light at all, especially the smaller tips. And the valves seem really stiff and hard to turn—is my torch defective?
A: This takes a little practice. But open the acetylene valve just enough to light, and then also barely crack open the oxygen valve. Done right, it lights to a flame with enough oxygen already there so it’s not sooty. Done wrong, you get a nice loud bang. The trick is just to use a tiny bit of oxygen. Just open the oxygen valve enough so it’s no longer closed tightly. Then, if it’s still too yellow and sooty, the valve will at least be quick to open further.
The other method is to have the acetylene valve open enough so it’s a pretty fast flame that ignites, even if it’s only acetylene. On some torch-tip combinations, that results in a yellow flame, but one which drags in enough air along its way so you don’t get much soot. This doesn’t always work with all torches, though. Light the fuel gas, adjust for a suitably-sized starting flame, then add oxygen or air to get a good usable flame. Then adjust the size or intensity as needed with either or both fuel and oxygen. By the way, if when turning on the oxygen, you then can’t light it until you add more fuel gas, then it’s a crap-shoot as to whether you’ve got a usable mix that you can ignite. Too much oxygen, and it won’t light, or will try to light but just “pops” and goes out again. If you use more than enough acetylene, that’s a variant of your “fuel first” method.
In short, do it wrong, and it basically just won’t light, or won’t light as easily. But don’t worry—nothing you’ll do in lighting the torch will actually blow up or damage the torch. However, when turning it off, if you turn off the fuel first, then the flame gets sharper and sharper until it goes out, but in going out (especially with larger torchs and torch tips), you can get a loud “bang” noise. This is indeed a tiny explosion, but other than startling you, will do no great harm, unless jumping when being startled causes something unfortunate to happen. Do this in a workshop with other people, and you can annoy them. But you will not have damaged the torch. I’m not sure if the microflame torch will even produce a large enough flame to get a noticably annoying pop when extinguished this way. Welding torches, and metal melting torches, larger soldering torches, yes. Tiny ones, Little Torches, etc., not so much.
Try to avoid any wind, including fans blowing across your soldering area. Many jewelers’ torches get really hard to light in any sort of breeze. If you’ve got the garage door open for ventilation, close it enough so there’s no actual breeze in your work area. That will help a lot. Barring that, you’ll do best to set up some sort of wind screen so you’re at least lighting the torch in mostly still air.
When new, the torch valves can be pretty stiff at first. But you might also try very slightly loosening the larger hex nuts at the base of each valve. I don’t recall if this is the case on the Little torch, but on many, that nut, actually part of the valve body where it screws into the torch handle, is also part of the packing/sealing system to keep the valve stem from allowing a gas or oxygen leak. If that’s the case, slightly unscrewing that from the torch body will ease the tightness with which the valve turns. Don’t overdo it, or you’ll get the leak the packing is intended to prevent. If it doesn’t help, then I’ve remembered the torch construction wrong, so tighten it up again. Either way, it will loosen up after you’ve used it a bit.
It also sounds as though you might have the tank output pressures set too high. The Little Torch uses gas and oxygen pressures a good deal lower than most other torches. Try unscrewing the regulator handles a bit to get lower pressures. That should help a lot with the torch flame blowing out. If you’ve got the usual standard little torch kit, they usually supply it with the same set of tips no matter what fuel gas you’ll be using. With propane or natural gas, the first three tip sizes, #1, #2, and #3 are pretty useless. You can, with low regulator settings, get the #3 to light but it’s good for only the tiniest of soldering jobs. The #1 and #2 are almost impossible to light at all with any flame stability, though sometimes you can get a faint tiny flame useful for polishing details on wax models. But that’s about it. In general, for actual work on metals, you’ll be using the #4 and larger tips with propane and oxygen.