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How to frost acrylic?

Hi Guys,

I'm making a project in which I will need to frost the acrylic (3mm plexiglass) and since frost paint or frosted acrylic is not available around here where I live I will have to use sandpaper. Last time I tried frosting acrylic (6mm plexiglass) with sandpaper (which was 180 or 280) I kinda succeeded, it was frosted ...... until I dropped water on it. What I was left with was lightly sanded acrylic with lots of scratches so I was wondering if anyone could tell me which sandpaper should I use and how should I do it.
 
Thanks in advance :)

-Prickly Potato

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When I do it I do it under running water.

Depending on the size in the sink, bathtub or outside with a garden hose.

I have two different ways of sanding, depending on how I want it to look.

Standard for smaller panels:

Keep wet and use 600 or better 800grid sanding paper (the kind used for working wet, not the cheap paper sheets).

In a circular motion I start from the edges and work my way to the center.

While the whole sheet is wet you can tilt it against the light and sport shiny areas right away to be sanded again.
Keep doing it until it all look even.

Plastic with a protective shield against scratches and UV aging is a bit tough at the beginning and you can spot it as you can see clear lines around the unsanded areas - this is the layer coat.

For bigger sheets I usually prefer a sanding block to have a greater area to work with.

But I do it in three rounds, first horizontal, then vertically and last diagonally.

Once all is looking good and give it a quick finnish with a circular motion.

No matter what you do, once a film of water is on the sheet it will appear clear again, that is due to the refraction and properties of water.

Same way you can look thorugh a piece of paper using oil.

For a more aggressive finnish you try "sanding" with stainless steel or copper pot scourers, these things to clean baked on food from your cooking ware.

Use rubber gloves (best are nitrile ones) and while rubbing down the plastic spray a light film of acetone on the area you work on - please do this only outside!

The acetone will soften the surface, the pot cleaner will scratch it and move the soft plastic around.

Takes a bit of practise to get the right amount of pressure and spray right but works great.

Just spraying the acetone on a flat laying sheet works too, but the results are not to my liking (personal opinion).
If you don't mind the feeling and look you can also use very fine play sand to dust the whole sheet and once happy with the look spray it with acetone, the sand will "fuse" into the plastic and you made an acrylic sanding sheet ;)

+1

verence2 years ago
The Prickly Potato (author)  verence2 years ago

Thanks

rickharris2 years ago

You should use something very fine. As fine as you can get really and work over it for a long time to get an even frosting. The is best done by hand. power tools tend to over heat the acrylic and score it or give an uneven finish. Use a sanding block to get an even finish. I have always used wet and dry paper as used to rub down car bodywork rather than sand paper. It lasts longer and gives a finer finish.

It will still look rather clear when wet but so does standard frosted glass.

If you can find someone to do it it could be sand blasted.

You could apart from the wet bit stick tracing paper to the back side

You can as you say buy frosting sprays some are not water proof.

The Prickly Potato (author)  rickharris2 years ago

Thanks