Well, now I've done it.

Especially for the bottom 3 feet (it does cost more than sheetrock, so you might not care to do the whole interior with it) consider either "hardibacker" or "Durock" - the 3x5 sheets of cementboard, or in the case of hardibacker, similar (and easier to cut), material sold for tile floor underlayment. Harder to punch a hole in, more fire-resistant (no paper face). In drywall, do choose the Type X (firecode) for obvious reasons.

In the "I don't know where you find it conveniently" category, a surface for better sound adsorption would be finely perforated steel sheet. Morton Buildings was pushing that when I was shopping around for buildings some years ago. The holes would have to be smaller than a spark. Theory being that the sound goes through and gets soaked up by the insulation.

Whatever you use, run a full bead of cement/tile grout/drywall compound around the floor/wall join, and the wall/wall joins - sparks getting into crannies are bad news when the building frame is wood. Eliminate crannies. Cast a critical eye at windows, window frames, door frame, sill as if you were a spark and wanted to find a nice place to hide...

Promo,

No help with the drywall but serious kudos for getting closer to a coal forge. I have worked both coal and gas for years and am a huge fan of the coal. Charcoal? Hmmm. Go with soft coal and you will be soooo happy. Charcoal is extremely dusty and gets in your throat. I do not think it is a good idea for long term smithery. Knife makers may disagree but most of them have gone over to the dark side (propane) anyway.

Good luck with your forge!!!

Andrew

Drywall will be more than sufficient. I use drywall sheets on my glass bending and blowing benches. All great blobs of red hot glass do is char the paper a little. No flame at all. The paper has some sort of flame retardent in it that will not let it flame. I occasionally do some welding/cutting on one of the benches with no detrimental effect. This is just plain old drywall laid on top of a plywood deck and not the green fire rated stuff.

I used Hardieboard (the very smooth kind that Lowe's sells) one bench but it was too thermally conductive and would shock the glass. It's gone.

My main glassworking bench is >10 years old and is still in fine form.

John

Ah, yes- hardibacker. I hadn't thought of that, but that wouldn't be a bad choice. I'll steer clear of cement board, though- I have a long standing dislike for the stuff from past tile jobs.

Oddly enough, I might be able to get my hands on that very conveniently- though whether or not I can *afford* it is another question altogether! Any idea what the diameter of a hole "smaller than a spark" might be? We get some perforated steel in at work on a semi-regular basis for a customer that has us cut speaker screens for them. The holes are about the size of a mechanical pencil lead. If it won't require a second morgage to buy it, I might try that out and see how it works.

Another good one I hadn't thought of- thanks for the advice! I've done plenty of construction in the past, but nothing where there was going to be open flame and hot metal moving around on a regular basis, so I hadn't considered some of these things.

Yeah- charcoal was just a brain-fart on my part. I should be able to buy coal from the local blacksmithing group- they seem friendly enough.

Am I to take it that you guys don't paint your shops? I'm not too concerned about the paper starting on fire, as it will be covered with whatever color paint I've got down in the basement. I guess my main concern was the large amounts of water vapor that the propane forge generates turning the drywall into a big sponge, even with the vent fans. I suppose to be on the safe side, I'll just get the green-edged bathroom stuff and tape it with durabond.

Nothing worse than drywall that has gotten wet- it's really soft, and puffs up like a marshmellow.

Well, a screen manufacturer's site lists chainsaw spark screen as having

0.022" openings...on the other hand, typical fireplace screens seem to have much larger mesh.

Super-Trapp's description of their screenless spark-arresting mufflers mentions a 0.023" spacing as part of the design.

0.5mm pencil lead is 0.019" if I'm converting properly

Sounds a bit like a "davy lamp" - the mesh actually conducts heat away from the spark, causing it to extinguish.

I can't find an online reference to gauze size, but the sort I've seen had a mesh size of 16 holes/inch - much larger than you are quoting.

I would think that chainsaw sparks would be travelling much faster than welding or forge sparks - this may mean the gaps need to be smaller.

Hmm... I'll have to check the price on the stuff. I'm sure it costs more than drywall, but if it's within financial reach, I might try it out.

My friend used metal sheet roofing on the walls over insulation, already painted, spark proof,moisture resistant & easy to clean. He used 1/4" x 3" bar stock for base"trim" in his forge area keeps sparks out and you can brace things against it as a bonus. Sheetrock works well too but can be damaged easily in a shop environ. also unless you paint it the grey color sucks up an enormous amount of light. Unless you are going to create a fire rated envelope (walls & ceiling rocked Dbl. 5/8's everything taped and all penetrations sealed w/ fire caulk give 2hr rate) regular 1/2" rock will do you just fine. For insulation I like foamboard cut into the stud cavity and foamed in place, in a shop I think its more important to control the air infiltration them to have a high "R" value.

just my ramblings YMMV

Andrew