Blistering From Paint Mask Removal

I'm going to give you two pieces of advice based on my experience.

1. Don't make signs this way. It seems like the smart way. Use one piece of material. Paint one piece of material. Use masking. What could go wrong? The answer is simple: This. Go cut the part out of another material (ACM, Acrylic, PVC, Aluminum. Whatever you think is best for the application). Paint it. Gold leaf it. Then glue it down. Building the signs in pieces and assembling after is just way easier and far less likely to have things go wrong.

2. You're pulling the primer off so the primer is the issue. Could be the actual primer that's gone bad. Could be, despite your attempts, not applied correctly. The thing with HDU/PVC is it doesn't absorb paint. So all the drying needs to go one direction. So if it says "Dry for 4 hours" that means "Dry for 24 hours". If you're putting down oil or latex paint, you have to let the stuff dry a ridiculously long time. My gut says you let the one shot dry long enough but not the primer.

Either way, paint the sign. Cut out the crest. Finish it. Glue it down. Move on with life.

 

I agree, the primer's not sticking, so despite your prep it's not clean enough, or it's not curing. 50 degrees isn't that cold, but it's also not great for curing so adding time to the process.
I think the suggestion to cut the shape from another piece of material that doesn't need any priming like ACM then applying with vhb and adhesive will rescue this job, and the client gets a little more dimension. When you paint the ACM you can bring it somewhere that is warmer till it's cured, or have some gentle heat blowing on it with a portable heater.

 

I have had the same problem.The primer not sticking to the foam.Especially any water base primers.I use stik-tite for primer now and never have a problem .

 

Maybe not related to your challenges, but wanted to share since we're talking about paint. Haven't experienced this on the front end, but more so after the signs are installed (and exposed to heat/moisture) The Sherwin Williams paint I was using would blister and boil up after being in the field. Water based paints tend to stay soft after they're dry, so maybe the "rubbery" attribute of the paint allows it to expand when heated?

To address this, I started using the Sherwin Williams DTM paint with success---it dries leaving a hard shell (much like enamel), but when mixing colors you still need to use traditional latex paints (DTM comes in black and white only). This seemed like a step in the right direction.

But.....I recently had a colleague turn me on to PPG paints, and they are incredible. Their primer is called "Gripper", and their waterbased line that dries to a hard shell is called "Break-Through". The "Break-Through" can be mixed to any color (with all pigments being of the same compatibility. Been doing signs for over 20 years, and this is by far the best, most durable paint I've ever used---dries to a hard shell like enamel and lays flat on surfaces---never looking back.

 

If you tinted your size, you tinted far too much, unless you're just putting it on too thick. Also, are you waiting for the size to almost dry before lifting the mask ?? If so, you should remove the mask almost immediately. As for temperatures, 50º is fine, just not comfortable for you. I like the idea of gilding a separate piece and just putting it overtop. done this many a times.

 

On something 1/8-1/4" thick, it would be VHB and glue. On 1/2"-1" thick, it would be studs, VHB, and glue.

 

You're not using foam tape. It'll only be the thickness of a pubbie hair.

 

you lost me at the glossy background texture. lol
....but +1 to making separate pieces for separate colors, whenever possible....without piling-on material costs, of course

masking-off dimensional pieces is a PITA, and opens the door to misc. failures. individual parts assembled always has a cleaner-finish, and allows for quick&easy-fixes to mistakes along the way.

 

We usually rinse off our HDU signs in addition to blowing off the dust prior to painting. Although HDU supposedly does not absorb water we wait 24 hours to make sure the surface is completely dry before painting. I like the idea of the separate panel for the gilded area. It just seems safer. We have yet to find a fool proof paint mask that is problem free. BTW - that's a really nice looking sign.