# Polyurethane over poster



## Carloz (Oct 12, 2016)

I have a few posters that will be mounted in wooden frames. I have some water based polyurethane from the previous project and wonder if I can spray it over the posters. I also have some oil based polyurethane but am afraid it would make greasy stains in the paper.
Has someone tried that ?


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## mrbob (Nov 3, 2016)

I would be more worried about the ink base on the posters. I am not a printer but my brother was. The ink could be water or oil based. Using the same base finish over the ink may/could reactivate it and cause it to run.
Go with a sample if you can here. Shellac maybe your best bet, it wont reactivate oil, I am not sure about water base ink.


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## kelvancra (May 4, 2010)

It'll work fine. Just mist your first coat to seal, then go from there. That's how I started out, before going to two part mixes. Even then, I used poly to seal the paper, after gluing it down.


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## dhazelton (Feb 11, 2012)

A. Don't do it if they are valuable.
B. I'd go to a craft store to see what they use. Personally I'd put them under glass or plexi.


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## kelvancra (May 4, 2010)

dhazelton reminds of a good point, regarding value, but as to the poly, I am the professional on this matter. I, literally, have done a few thousand posters and prints. Among them were even done a few pen and inks.

The only time poly wouldn't work is, if the item you are finishing is something like a newspaper or magazine clipping. If you used it on those, it would soak in and cause bleed through of the print or pictures on the back.

To avoid bleed through, if applicable, I just used the same Elmer's I used to glue the picture. Once I'd sealed the item with that, I was ready to pour the resin, which I bought in five gallon containers.

You could use ModgePodge or even Elmer's or other white glue, but the poly was my go to.

Since you're spraying, it's even less likely you would cause problems to any ink on the poster. I always brushed, because it was just more convenient to me.


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## wormil (Nov 19, 2011)

Thanks Kelly, I work in printing and always wondered if poly would work but never had reason to try it.


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## Carloz (Oct 12, 2016)

Thanks for the advises. I tried it today and the results beat all expectations. I sprayed one thin and two thick coats of HF semigloss water based polyurethane. After it dried the poster appearance did not change at all, the same sheen and no sign of the clear coat. However it it there and gives it excellent protection. You can trow water or anything on it and it does not care. Unprocessed posters immediately get wet spots. You cannot scratch it so easily and if you manage to write on it easily wipes off. 
Polyurethane does dry much slower on paper than on wood.


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