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Originally Posted by firefreak
When turned down to a low flame the combustion can take place right on the face itself. on very low flame it can take place in the port tubes. Propane oxy mixture burns at 3900 deg F. mild steel melts at 1600 deg F. Stainless and alloys are higher, but below 3900. So the danger is that if the torch was run on to low of a flame for a extended period ( the larger the torch , the shorter to time) the metal the face is made of would begin to melt. This is why its important to size the torch to the work you plan to do. Running a large torch on low settings is just asking for problems.
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One thing I will add is that running a large torch on low settings is problematic if you are running the whole torch. If it is a large torch with a centerfire, then just running the centerfire of that large torch will not be a problem. But, yes, if you are running the whole thing on low settings, then it can cause problems.
I think where most people run into problems is when they want a broader flame for say long beads. They don't need a lot of heat, they just want it to be spread out so they can keep their long bead warm (there are other methods of keeping long beads warm, btw). So, they get a torch that has a wide face and then just run it low. Perhaps a better thing to do would be to adjust the flame and work farther out. There are a couple of ways to do this. One is to add more oxygen to the flame and work where it feathers out. Another method is to add air to the propane to thin it out and weaken the flame. Yet another way to get around running a low flame on a big torch to keep a long bead (or other object) warm is to learn how to move the glass in the flame and balance the heat.
When I bought my Phantom, it was because I was starting to make bigger things. I thought that I needed the wider face/broader flame to keep the bigger things warm. Well, now that I have some more experience under my belt, I find that I use the centerfire (the Lynx) for the some of the same things I originally bought my Phantom to do. I do not use the outer fire to keep bigger things warm. I move the glass and balance the heat. The outer fire comes in handy when melting huge gathers quickly and working murrini (haven't made one in a while - will have to do some soon). But really, I use the centerfire so much more than the outer fire for the stuff that I'm doing now (soft glass).
So, when moving up to a bigger torch, I suggest looking at all your needs and weighing them carefully. If you just want a big torch, that's one thing - go for it, it's fun. But, if you think you
need one because all you need is a way to keep long beads from cracking, and otherwise, you're happy, then take a look at how you're working - maybe a few modifications can make all the difference you need. Does that make sense?
PS I wanted to add that I am still happy I bought my Phantom because I did need it for some of the things that I was doing and things that I still plan to do (like more marbles, paperweights and some bigger boro sculpture). But, if all I needed was to keep long beads warm, then it would have been unnecessary.