I do not believe a heat gun will produce enough heat to dissipate the moisture in the steel, mold, or other material.
I spent a winter - freezing rain and snow at no extra charge - cadwelding impedance bonds to railroad tracks.
We used propane (maybe MAPP???) tanks. 99% of the welds were good on the first shot. You need a lot of heat to remove the moisture from a rail! The same gas also made short work of heating/removing moisture from the molds.
A few tips:
Before shooting the weld, pack the exterior edges with duct seal. If for some reason the mold is not completely seated, the material will come right out, and erupt on impact.
Don't breathe in the smoke...either get your face out of the way or pay attention to which way the wind is blowing.
Keep a fire extinguisher or sand handy. If the material escapes, it WILL ignite other objects.
A grinder. If the object you are welding to is not clean - you will be shooting it again...after you clean off the first "opps". A cold chisel and a lump hammer work for "tight" spots (saftey glasses/goggles too).
Welding gloves. Depending on the size and/or number of welds you plan on doing, these might be a must. Don't use ANY gloves that can ignite (ie, cotton) or "shrink" when heated (ie, ANY rayon, polyester, etc blends)
If you run out of "pennies", a piece of paper will suffice (on large shots, I wouldn't reccomend it on small shots)..but don't make it a habit.
Try a few "dry runs". Create an ideal situation and give it a go.
Visit the
[Erico Site] (Cadweld is one of their brands):
A work of
CAUTION:
Keep a first aid kit handy
I had a guy who had never welded work with me one summer...I told him the molds will be EXTREMELY hot after shooting them - DO NOT TOUCH THEM. Well, he reached over one (hot) mold to grab a cool one and now has a nice square burn mark on his forearm....thankfully, we had the first-aid kit with us.