Vincent, I had the pleasure of using ng/oxy torches at my last
school. Intensely and for months on end. I really liked the
natural gas oxy combo. While not as hot as oxy propane, the flame
seemed softer and more adjustable. Soldering, I rarely had
firestain, and the pinpoint flame, compared to air/fuel torches,
made tricky solderings a snap. However, natural gas/ oxy is not so
good for casting. For large charges, one needs a pressure booster
to up the line pressure from the 3 to 5 PSI (something like that,
where I was) in order to get any power out of a large torch, and
there seemed to be some issues with contaminants from the burned gas
entering the alloy...some porosity and brittleness, even with care.
This is only my experience, and that of my classmates, so maybe
those more skilled have the casting thing dialed-in. Also, forget
casting Platinum with the Natural Gas Oxy system, it was a pain.
Bottom line--I liked it, but it's not for everything, I think. Danny