It is always best to have your regulators set on the highest pressure recommended, regardless of the glass you are using. That way you will have the gas (fuel/oxygen) there when you need it.
Your needle valves control the flow. If you have your pressures set high, you can always control the flow through your valves and have as little or as much fuel or oxygen go to your torch as you need.
Here is an example of why you should not set up on the low end:
Say you are making a marble. You set out to make it one size, but it starts getting bigger than you anticipated. You need more heat. Now, if you are already set to the maximum pressures, you just turn up the heat by using your needle valves. But, if you were set up on the low end, you will have to go change the settings on your regulators to allow more fuel and oxygen to get to your torch.
There are many reasons why you would need higher pressures:
- long of lines
- multiple torches in line
- flashback arrestors in place
- elbos in a hard-lined set-up
- restrictions (e.g., hose connections, nipples, etc.) along the line
So, what I am trying to say is that you can never use less. You might as well start off with the highest recommended pressures given by the manufacturer.
The
only torch I know of where you really need to change the regulator settings to get certain effects/colors out of glass is the Herbert Arnold. It has a single control knob and in order to finesse the torch, you adjust the pressures with in-line regulators (you could adjust them at the tank, but lots of guys put additional in-line regulators right at the torch so they don't have to run back and forth).
You do not need to run different pressures for different types of glass because you control the mixture and the amount of fuel and oxygen with your needle valves. Running low pressures for working soft glass is not only unnecessary, in the case with some torches, it will carbon them up pretty quickly. It is better to run them at the highest pressures you have available to you (within the manufacturers recommendation - do not exceed their valve tolerances) and to control the flow with your needle valves.
Oh, and when you set your pressures at the regulators, make sure that you go back and adjust them while your torch is running. If you just set your pressures, and then go to the torch and start working, the pressure will actually drop lower than what you set. So, you need to set your pressures, go light the torch, and while the torch is running, go back to the regulators and adjust them to the proper setting.