Masking Paper

[Ernie Martinez]

I purchase a roll of masking paper from Laserbits a while back. I just did a reverse engrave on some acrylic. I painted the back (used Valspar Paint for Plastic), let it dry overnight. then masked it, engraved the letters, let it cool for good measure, then painted the fill colors, and let it dry for 2 hours. I just peeled the mask, and I don't know if it's the new coat of paint reacting with the first coat (can says apply subsequent coats within 8 hours), or if its the mask I'm using. Or possibly something completely different. The pic shows the more severe problem but the edges of ALL the characters look like. The masking paper I'm using is "Transfer Rite Ultra".



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[Dan Hintz]

Are those surface whiskers (i.e., they can be scraped off), or has the surrounding plastic cracked and let in paint? If it's surface whiskers, your mask isn't tightly held to the surface (been there before). If it's cracks, make sure your paint is rated for use with plastics.

[Ernie Martinez]

The paint cracked, doesn't seem to be anything wrong with the acrylic, just not a crisp boundary at the mask.

[Joe Hillmann]

It is caused by spraying the second color to heavily and the solvents get sucked into the already dry paint. The best way to prevent it is to use several VERY light coats of paint rather than one or two heavy coats.

And when I say light coat I mean so light it is dry just seconds after you spray it.

Edit: I am assuming the cracking is where the two colors of paint meet up. Although spraying to heavy of a coat can cause almost the same problem with the adhesive on the masking.

[Lee DeRaud]

If it's surface whiskers, your mask isn't tightly held to the surface (been there before).If I'm reading this right, the paint bleed is between the background color and the acrylic, not between the mask and the paint.

[Lee DeRaud]

One thing I'm not getting here, assuming all the painting is done on the back...

If the background color is sprayed first, you can just raster off the letters and spray them: no masking required. Or the letters can be sprayed first through a vector-cut mask, and then the whole background painted over it: no paint rastering required.

I'm having trouble coming up with a scenario where both paint rastering and masking is required.

[Ernie Martinez]

Thats probably my problem, I really laid the paint down thick? I'm also going to give liqua-mask a shot rather than paper. It was also recommended that I use X-I-M Primer. My problem is that the letter fill paint is causing the background paint to flake at the intersection of the two.

[Ernie Martinez]

You have a point there, but according to the instructions, the second coat must be applied within 8 hours for some reason.

[Dan Hintz]

If I'm reading this right, the paint bleed is between the background color and the acrylic, not between the mask and the paint.

Thanks, Lee... I guess I misunderstood what was being shown.

[Joe Pelonio]

If you spray with an airbrush, it dries almost before it hits the plastic.:eek:

Seriously, by the time you get to the last letter the first is dry enough for another coat.

[Bill Cunningham]

Before 8 hours depends on the drying conditions. Many paints use a 2 hour maximum window. If the second coat is not applied within the 2 hour window, then a wait of at least a week is needed for the first coat to fully cure before the second is applied. Both types of paints must be compatible or there is a good chance the final coat will wrinkle. But Lee is right, there is really no need for masking at all.

[Ernie Martinez]

Just did a reverse engrave and paint using Krylon FUSION as Tim had recommended. Works like a charm! That Valspar Paint for Plastic is junk, at least for this application. Doing the front engrave now with a paper mask, I'll post how that comes out.

Thanks for everyone's help.