New to HHO builds, questions, comments, and kangaroos.

Jumping right into it: I'm working on my first HHO build and I'm starting off with dry cell. 22 6x6" 18g 316 stainless plates, two "+nnnn-nnnn+" cells side by side, KOH electrolyte. My initial testing is going to be run off a 9-14vdc 40amp adjustable power supply but that may be stepped up as this isn't going in a vehicle (as of now).

I'm putting together my parts list, but I've got a few questions that I'm having trouble finding answers a couple of materials.

I'm aiming for a 1/32" gap between plates, my understanding is that most of the electrolysis only happens directly on the surface of the anode. The thinner the gap, the smaller the resistance. The materials however are where I'm getting befuddled. For KOH the two best materials I'm seeing are Nylon, and "Buna-N" or Nitrile. I've also heard EPDM bounced around a lot but I don't see many reasons other than availability behind its usage.

Up next is about the end plates. There are three materials I'm looking at, Nylon (again), Micarta, and Acrylic. All the info I've seen except for the info on Micarta is very conflicting, but I can't find a supplier for the Micarta that doesn't want my left leg for a suitably thick piece. I'm looking for longevity and efficiency, not exactly cost, but face it: I'm not making my plates from platinum.

I understand the need for flashback arrestors, the reaction between hydrogen and oxygen is what's used to launch space shuttles, but what the heck is the percolator (bubbler) for? I read some threads that claim it smooths the flow, some that claim it helps dry it out, still others that claim it removes any fumes left from your electrolyte. What's the deal?

Finally PWM. I've read a bunch the threads on here and elsewhere that mention the resonant frequency of water, but as far as I can tell the PWM circuits used do nothing of the sort. They just pulse the current to help control temps and/or power consumption. Can anyone explain?

As for what my end result is, I'm working towards an HHO torch/foundry. The heat produced by the HHO torch is comparable to any electricity based welder I know of. Storage of welding gasses isn't an option for my workshop either, and I can think of a few friends who would benefit from such a setup. Thanks in advance for all your advice!:D