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Polishing Acrylic Edges

Discussion in 'Scenery, Props, and Rigging' started by bobgaggle, Jun 21, 2019.

  1. bobgaggle

    bobgaggle Well-Known Member

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    We do a lot of acrylic stair treads and usually flame the edges with mapp gas. works great, but there's a lot of prep work needed to get a perfect finish. And we do go for perfect. No bubbles, burned in fingerprints, dust specks melted in, that kind of thing, that ghosty haze that happens sometimes. A guy told me his old shop never flamed and used buffing wheels on a bench grinder. The stacked up fabric wheels and some really fine polishing compound. I had never heard of this. Anyone use a method other than a torch to polish edges?
     
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  2. mwasser

    mwasser Member

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    Well this wasn't in a theatre at all, but from when I made some scientific instruments. Polishing acrylic absolutely works, though, and I've never thought about using heat to get a smooth surface.

    I started with a very fine grit sand paper, then polished with felt and putz pomade, and then with felt, alumina powder (0.3 micron, as I recall) and a bit of water. The sandpaper took care of the marks from the saw, the putz pomade smoothed out the marks from the sandpaper, and the alumina powder got it nice and shiny. It was a small amount and we didn't actually have a buffing wheel, and so just did it by hand on a table. This was to make reflective surfaces for scintillators for in muon detectors (basically trying to trap faint flashes of light inside a sheet of fancy plastic), and it worked very well.
     
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  3. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    The last time I polished an acrylic edge I used a bench grinder with a buffing wheel and buffing rouge. That was grade 7 shop class though.
     
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  4. Van

    Van CBMod CB Mods Premium Member

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    Yes, you can use either. Flame polishing has the drawbacks of edge mushrooming, possible bubbles and overheating. I've also used a solder re-working heat gun for edges. no chance of the material catching on fire but you run the same risks of mushrooming and melting. For Museum pieces I've always relied on a cotton buffing wheel and ultra fine grit polishing compound <white>. You can still over heat the piece by staying in one spot too long. You can warp an area on a flat face if you don't keep the work piece moving.

    You prep the edges the same way you would if you were flaming, use a razor or plane to square and smooth the edge, then polish with the wheel. Easy peasy.
     
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  5. bobgaggle

    bobgaggle Well-Known Member

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    Preference or do you think one is better than the other? I'm looking for something faster and less error prone, but from your description it seems like prep effort/time is the same and risks during polishing are similar too... one of the main benefits seems to be that you don't have to peel the work piece if you're mechanically polishing. With flame you have to peel both faces and leave them exposed to damage...
     
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  6. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @bobgaggle When flaming, do you need to peel all of the protective paper or can you peel both sides back two or three inches, flame, and then lay the edges back down for protection, possibly with a little tape to hold them in place?
    Toodleoo!
    Ron Hebbard
     
  7. Van

    Van CBMod CB Mods Premium Member

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    I prefer polishing with a wheel all the way around. My caveats were just meant as a way to say, "there are still risks" but they are much lessened with a buffing wheel. Oh keep it at a slower setting if possible.
     
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  8. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    Since we're on the topic, what would you use to laminate several sheets of say, 1/4" acrylic to make a 1" disk? I have a project that needs an orange disk but can only get the orange in 1/4".
     
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  9. eadler

    eadler Active Member

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    I haven't tried laminating but I would think that a liquid acrylic (sold in bottles as Pledge/Future/other-brand "floor gloss" or "floor finish", might be scented) may work well (or it may work disastrously! try it on a scrap first). You might need to scuff the sides to adhere better (the liquid acrylic will probably bind better to a scuffed surface and you will no longer have an optical transition once it is applied).
     
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  10. Van

    Van CBMod CB Mods Premium Member

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    The liquid acrylic glue used for edge gluing will do it, and will completely disappear, but it's a one-shot deal. if you pull it apart and get any air bubbles, or ridges of semi dissolved acrylic the piece is ruined.

    They do make acrylic dyes...

    TAP doesn't have Orange in 1/2 or 1"? Weird.
     
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  11. bobgaggle

    bobgaggle Well-Known Member

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    Good luck. I don't do a lot of it, so someone with a more practiced hand would get better results, but this is the result I got from laminating 2 pieces together. lots of what van was talking about. This method was to lightly clamp the work pieces together with spring clamps and use a needle applicator to the seam, letting the solvent get drawn into the joint. Couldn't get enough penetration. On the other end (not pictured), i flooded the face of one piece and laid the next piece on top. No ridges, but lots of air bubbles....
    IMG_8630.JPG
    This is the body of the pin ball plunger I just posted a new thread about.
     
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  12. bobgaggle

    bobgaggle Well-Known Member

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    We usually do 10" treads, so by the time you peel back enough paper on all edges to get out of the way of the flame, you've pulled off the whole thing...
     
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  13. DIYLED

    DIYLED Active Member

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    Occupation:
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    If the edge is rough, it might be easier to first start off with a mini sanding tool that has a ball joint, then use a polishing wheel. The type of acrylic work I do is usually different than what most people are doing, but once in awhile I'll do something similar.

    Acrifix 117 w/ Serrox capillary activator is a good choice. Works better than Weld On and less toxic. To really eliminate bubbles it takes practice and fine-tuning the shim size (0.002" to 0.006" fishing line) and the time to pull shims which all depends on temperature and type of acrylic. Sometimes small bubbles form as the glue cures. You can mix some Acrifix 116 to reduce this but the tradeoff is less capillary action.

    I've heard that some professionals use Evonik's UV-curing glue which might have the advantage of being able to a re-do if there's a bubble. I haven't used it.

    Some people use a 2-part PMMA paste which has to be mixed.
     
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