Oramask peeling off paint or something else?

I primed the MDF, painted, sanded and painted again. I masked it with Oramask 813 and then cut. After the cut, I sprayed with primer and let it dry for a few hours. When I peeled the mask, this is what happened.

I’m not really sure why it did that. I’ve done the same process before with no issues. The only difference I can think of is that the mask was on longer than normal because I had a belt break near the end of the cut and finished the next day. I’d appreciate any thoughts.

I always paint then seal it with poly or sanding sealer. Ussually 2 coats and let it sit overnight and have never had a problem like that.

I have recently been working a lot with Oramask and have done a write up explaining my process.

I would most likely guess that the cause of this is leaving the Oramask on too long. I have noticed that on plywood, when left on too long, the Oramask will peel up chunks of the veneer.It is some pretty strong stuff. Another issue could be with how long the spray paint was left on top of the Oramask. I try to just let it dry enough so it doesn’t run. The sooner you get it of the better in my opinion.

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Agreed. A combination of both the oramask being in too long and the paint not being fully cured looks to be the issue in OP’s case.

hi there. i am new to all of this and was introduced oramask. just wanted to make sure before i test it out…you applied the oramask to the plywood first and then did your carving?

Yes. Apply your oramask and then cut. It is some pretty tough stuff. Good luck!