Flame Polishing Acrylic?

[sweetnothing]

Anyone here flame polish acrylic? I've got several 3/8" thick acrylic shelves I'm adding to my entertainment centre and I've found out one can flame polish the edges instead of using the labour intensive sanding and polishing compound.

It's suggested to use a hydrogen/oxygen torch with a fine tip to polish the acrylic. Not having the equipment to accomplish this, I'm wanting to know if I can get away with a simple propane torch to do essentially the same thing? I'm willing to spend a little money here, but not what I'd have to spend for a full welding setup.

Thanks

[Chris Friesen]

I've done it with a little propane torch, but I started with jigsaw edges so the results were smooth but not perfectly straight.

Worth a try, anyways. The torch is useful for various homeowner tasks as well (especially if you have copper water pipes).

Chris

[cselby]

You can also put the piece in the oven if it will fit at about 300 F and keep an eye on it over 15/20 min. Laying it on a flat object will keep it from sagging.

On the other hand it gets to be stinky and your wife will likely butcher you in your sleep.

P

[klaatu]

I used to use a propane torch all the time to polish acrylic. The technique I use is to pass the flame very quickly over the edge. Keep repeating in the same direction until you see it start to get glossy. Something like spray painting having the trigger on only in one direction. Acrylic burns if you leave the flame in one spot too long. The surface should be flat to start.

[BrianInHampton]

[Upscale]

I've just experimented a bit with a piece of scrap. The edge of the 3/8" acrylic was shiny and clean when finished and I can't complain about how it looks. However, about 1/8" close to the edge on the face part of the acrylic, the part one would look through, was visually distorted. I'm not sure if it was my technique or something else. I'll have to experiment a little bit more.

On another piece, I used a cabinet scraper to give me a flat surface with the saw marks removed. I then used some 400 grit sandpaper to smooth it out and give me an even and flat, but opaque surface. I've left it for now and when I get back to it, I'll use a buffing wheel and some compound to see if I can get that transparent, shiny surface similar to what the guy at the plastics store did on some other shelving.

[hex]

I've done a fair bit of optics with acrylic sheet ( stuff like www- physics.lbl.gov/~spieler/physics_198_notes_1999/PDF/IV- Scintillators-3.pdf from a quick google search ). If you care about optical clarity, I'd avoid the flame. Start flat and smooth (not a bandsaw, but table saw or better yet milling machine). Work your way up through the grits to about 2k-4k, *gently* VERY *gently* hit the buffing wheel and at the end use regular old white copier paper as a final abrasive.

The funny thing about when flame polishing comes up in an online forum is that the discussion starts out with "I want a quick way to smooth and polish an edge" and it ends up with "I'm not happy because my flame polished edge isn't perfect." Ya gets what ya pays for. Photons are unforgiving. Be glad you aren't trying to make mating clear surfaces -- then you often care about the edges being

*straight* too.

hex

-30-

[Upscale]

I haven't seen a grit (sandpaper anyway) that goes above 600, not sure where or what I'd use for 2-4k. I did buy two new buffing wheels, with one supposed to be a little coarser than the other. It might be a wasted effort, but I'll try out the coarser one first and see what kind of surface I get. These are doors for an entertainment centre, so someone would have to looking straight down on the edges to really notice if the edges weren't perfectly transparent.

Thanks for the info.

[charlie]

auto stores carry higher grits. used for painted surfaces.

[Nova]

For sandpaper above the 600 grit range try an automotive store that sells painting supplies. It's used to rub out the final finish.

[J. Clarke]

Micro-Mesh is available up to 12,000 grit and in sheets up to 12x12. The manufacturer's site is

but has a much better interface and seems to have more product in stock besides. Note that they have packaged kits specifically for acrylic.

Its first use was to restore airplane windshields to full optical clarity, so it should do what you need.

You could also try sanding to 1000-1500 grit (try an auto parts or auto paint store) and then going after it with Meguiars or 3M polishing compounds (get them at an automotive paint store and ask which to use--there are a lot of them for different purposes and they are used in specific sequences).

[Tom Watson]

You can use a lower heat source and compensate with a slower pass.

Flamed edges are used often in commercial displays and the vendors are not fussy about the heat source.

Regards,

Tom Watson