Frosting acrylic - recommendations?

Machine Shop Plastics & Composites
#1

I’d like to frost some clear acrylic plastic sheet to use as s backlit panel. I’ve come up with three ways to do so, but I’m looking for advice on which is best, or any suggestions of another option.

Goals:

  • cheap
  • durable ( will be in full sun at 7,500’ - lots of UV)
  • easy(ish)
  • cheap

I’m considering:

  • sanding with fine grit sandpaper and a random orbital sander
  • blasting it with the vaporhone media blaster (assuming it’s ok to use on acrylic)
  • using frost spraypaint typically used on glass (though I’m concerned about durability)

Anyone with direct experience who’d like to chime in?

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#2

Use UV plexiglass and the random orbital sander. How big is the panel? I might have some free scrap UV Plex from work.

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#3

I’ve had the best luck wet sanding with 400ish grit sandpaper. Pretty prone to picking up scratches, but I assume it’s just as UV resistant as any other acrylic panel.

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#4

From memory, it’s in the neighborhood of 16x20. I’ll measure it in the morning to be more precise.

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#5

Lemme look tomorrow, might have that sitting around.

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#6

I have some clear acrylic that I think will work once frosted, but if you have some scrap that’d be awesome. It looks like 19.5”x22.5” would fit perfectly. No more than about 1/8” thick

It’s a replacement back for this outside wall decoration. It has solar powered grain of wheat sized bulbs going around the rim behind the front panel.

The original very thin plastic became brittle and fragmented after about one year in the Colorado sun. You can still see some few remnants I haven’t removed yet.

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#7

What about matte Mylar? Like Duralar? I got some at Asel that seems pretty beefy.

Edit: never mind. Looks like most Mylar products aren’t very resistant to us exposure.

#8

Hmmm, will have to poke around a bit. Don’t think I have anything quite that wide in my current scrap stash.

#9

I have a clear piece - I’ll try the wetsanding approach on it. Thanks.

#10

Sanding with an orbital is easiest. I made a backlit shadowbox for my brother last Christmas. Started frosting the Plexi by hand with 400 but it was taking too long. Grabbed the orbital, some 100 and 400 grit, and was done in 10 min or less.

#11

I have a random orbital palm sander I already intended to put towards the task. Thanks for the advice.

#12

You can buy frosted acrylic from any of the local suppliers, but if you want to do it yourself I’d recommend just using a random orbital sander. You did mention this is for a backlight though? In my experience frosted acrylic doesn’t diffuse the light source very well. There is however a color of acrylic that does; White 2447. Most suppliers should have that in stock, as it’s common for sign-making.

#13

I appreciate the advice, but buying a sheet of plastic, while efficient, doesn’t cover my stated Goals #1 or #4. If the sanding fails to give satisfactory results, I’ll keep this in mind.

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#14

That’s what I used on my cabin sign I made last year. It’s still holding up fine.

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