Removing paper backing from old Plexiglas

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Yesterday I was about to toss all the Plexi scraps I have because the paper backing is stuck on so tight it can't be peeled off. I decided to try laquer thinner, assuming it was going to melt the plexiglass since they were headed for the trash anyway.
I moistened a paper towel with it, place it on the paper backing and a few minutes later it had softened the backing enough so that I could peel it free (with a bit of work - the scraps are probably 25 years old).
The Plexiglas appears to be completely unharmed by the solvent, which really surprised me. I thought would cloud it or melt it. I am now going to try to figure out the best way to scale up the process to get the backing off some very large sheets of 1/4" stuff. If anyone's interested I'll post the brand of laquer thinner and the type of Plexiglas it's working on. I know I have some Lexan scraps mixed in, so it may only work on certain types of Plexi.
-- Bobby G.
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email.me:

Have you tried a heat gun?
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On 11/15/2012 9:05 AM, Doug Miller wrote:

wouldn't it be tricky to not melt the plexi too?
i know acetone will fog plexi, and ammonia products can lead to microfractures.
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Perhaps the lacquer thing was a matter of timing.
Don't use alcohol.
Greg
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news:1485578554374695403.015126zekor- <stuff snipped>

This 25 year old backing paper laughed at acetone, alcohol, turpentine, hot water, ammonia and more. Nothing softened the paper or seemed to penetrate. I was pretty shocked to see the backing peel away and the Plexi not be melted by the LT.
-- Bobby G.
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Why not? Alcohol won't harm plexiglass.
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On 11/15/2012 4:54 PM, Doug Miller wrote:

sorry, i meant ammonia.
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I agree with Frank. Plexiglas is just Rohm & Haas' trade name for a cast sheet made of a plastic called "polymethyl methacrylate" or PMMA for short. If DuPont were to make that sheet, it'd be called "Lucite", and if ICI of Britain were to make it, it'd be a sheet of "Perspex". They're all just trade names for a cast sheet of the same plastic.
PMMA is used to make good quality interior and exterior latex paints, floor finishes, grout and masonary sealers, Corian and other fake marble counter tops and women's nail polish. So, anything that dissolves PMMA will also dissolve paints, floor finishes, Corian counter tops, etc., including lacquer thinner, toluene (the principle constituent of lacquer thinner) acetone, alcohols (including isopropyl and methanol), xylene, MEK and paint stripper (aka: methylene chloride).
If it were me, I would wet the paper down with mineral spirits instead, and then wrap with Saran Wrap or wax paper to prevent the mineral spirits from evaporating. That will allow more time for the mineral spirits to penetrate to the paper/PMMA interface and dissolve the old glue there. Mineral spirits won't harm PMMA at all.
--
nestork


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On 11/16/2012 12:18 AM, nestork wrote:

I had some old pieces of red plex that I'd given up ever removing the paper. Tossed them in a bucket. Long story, but ended up with a plastic bottle of brake fluid that was leaking in the same bucket. The paper slid right off the plexiglas. It would be worth an experiment to see how long it would take to reach this state.
--


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....and they will work eventually. We used stoddard's solvent.
I would be interested in knowing about the brake fluid. We had some plexi that was years old and even stoddards required some elbow grease.
Another nightmare is masking tape on metal and allowed to bake in hot sun for a long hot summer.
nb
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I was very suprised to see that the plexi wasn't immediately melted. Laquer thinner seems to have that effect on most other plastics it comes it contact with. I'll take my camera downstairs to take some pictures. I used the lacquer thinner since I was about to toss the scraps and figured what the heck. Not sure how the technique will work on the big 4 foot sheets I have. I am thinking of some felt pads soaked with LT and then covered by aluminum foil to retard evaporation. Once it soaks through (and NOTHING else I have tried soaked through before) the backing gets gooey and (mostly) peels off.
-- Bobby G.
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Depends on how careful you are, I guess. It works for me.
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> backing is stuck on so tight it can't be peeled off. I decided to try

I tried everything. The heat gun doesn't seem to soften the backing but it does warp the plastic. Has it worked for you? Maybe there's a difference in heat output or technique.
-- Bobby G.
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Robert Green wrote:

There is a Chem-Peel product specifically for that purpose that is available from plastics suppliers. The laquer thinner may not cause immediately visible damage, it can appear days later.
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I looked for that the last time I went through this. Couldn't find it. Some chemical facial peels at spas showed up in the search. Lots of differing opinions how to do this, lots of different types of plastic, some resistance to LT, some not. One hint for large sheets came out of that search:
"To get the old paper off and even the new in large sheets we use a broom stick and two strong guys with big fore arms. You start peeling back the edge of the paper and then wrap it around the broom stick or other stick and start rolling it. Be carefull not the let it tear. this works great and when you are all done throw out the stick. We have also added wood clamps on the end of the stick to make it easier to roll up. We use a chemical called Bestine it is the best for removing gummy, sticky materials. It is used in the sign industry."
http://www.practicalmachinist.com/vb/general/ot-removing-protective-paper-plexiglass-194671 /
Found a post by you from the long ago past, too: (-:
http://www.homegardenguides.com/garden-forum/home-repairs-forum/86183-plexiglass-removing-paper-backing.html
Chem-peel - Specifically designed for that purpose and works very well without harming the plex. I got mine from a plastic supply house, imagine you'd have to do the same as it was clearly not a consumer product. Seem to recall it was made by something like "Ogden Labs" in Utah.
Pete C.
Thanks for your input, Pete.
-- Bobby G.
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On 11/15/2012 10:44 AM, Robert Green wrote:

Polymethylmethacrylate is susceptible to most solvents. I know you can use 15% isopropanol in water to safely clean it.
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On 11-15-2012 10:44, Robert Green wrote:

I haven't tried it on plexiglas, but I've often put stubborn glues in the dishwasher. Have yet to find anything that leaves even a trace after one cycle.
Of course I also haven't tried it on anything subject to water damage.
Also in the dishwasher: I bought a used computer which worked fine except that the keyboard must have been used for years to protect the table cloth from syrup and grease drippings. Dishwasher fixed that, too. Typing on it now. (You do have to drain them well and give them a few days to dry completely before plugging them in.)
--
Wes Groleau

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On Thursday, November 15, 2012 10:51:51 AM UTC-5, Robert Green wrote:

I use "Quick 'n Easy" Specialty Adhesive Remover by AUTOTECH. This stuff i s awesome. Just spray it on and let it soak in to the paper, then carefull y peel it off. Wet a shop rag with the spray and wipe away the residual ad hesive. It doesn't melt the plexiglass! Old deteriorated plexiglass with paper that's been sitting in the corner for a few years...no problem http: //www.autotechmfg.com/products.html John.
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On 12/8/2013 7:23 PM, snipped-for-privacy@gmail.com wrote:

This stuff is awesome. Just spray it on and let it soak in to the paper,
then carefully peel it off. Wet a shop rag with the spray and wipe away the residual adhesive.
By accident I had a bottle of brake fluid break open where it got on some red plexiglas that I had been saving, but could not get the paper off. It was not instant, but that paper came off in full sheets with zero harm to the plexiglas.
If I have the problem again, I will look for the autotech product. No - I know that I'm enough of a cheapskate, I'll probably go with the brake fluid again.
--


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I use Naptha as a general purpose solvent, it doesn't seem to do anything to Plexiglas.
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