Something better than paint for back-lit panels?

[Matt Davis]

I make a lot of back-lit displays and panels on 1/4" and 1/8" acrylic. My usual procedure is to spray the back side of the acrylic black, then engrave once dry. I then apply various bits of translucent colored acrylic from behind to add different colors and effects when illuminated. The issue I'm having is inconsistent results with the paint. It's incredibly frustrating to finish a display only to discover pin holes of light shining through where it shouldn't. It's not a big deal to patch some of these places either with more paint, or a piece of black tape, but when it happens underneath one of the colored diffusers, it becomes a real pain to repair. I clean and scuff the surface of every sheet before painting and still have issues. I've also tried various brands of paint as well, including Krylon Fusion. I think the actual problem is stemming from small motes of dust getting onto the surface of the acrylic and under the paint, keeping it from adhering properly. When it gets knocked lose during handling, it creates the pin holes. I try to my best to keep the spray booth clean, but continue to have the issue. So, I'm not sure what the correct answer here is other than painting in a hermetically sealed clean room.:confused:

What this all comes down to is I'd like to simplify the process, and get away from using paint altogether I've tried various reverse engraving plastics from Rowmark and IPI with mixed results. The biggest problem is getting it in the appropriate thicknesses, especially 1/4". I thought I had found the perfect solution (albeit expensive) with Rowmark Colorcast materials. It's cast acrylic, the right thickness, and available in the right colors. I ordered a couple sheets of both 1/8" and 1/4", but had to send it back as it was, one...badly warped, and two...when back lit had so many pin holes, it looked like a bright starry night. So, I guess what I'm wondering is if anyone knows of any other alternatives? Or, is there such a thing as an opaque black, laser-safe film that can be applied to the rear side of clear acrylic, then successfully rastered with the laser? Or, am I just going to have to continue mucking about with paint?

Thanks!

[Wes Mitchell]

I got through the first paragraph thinking Colorcast would be perfect, but then I got to the second paragraph :). I'm surprised you received a warped sheet of Colorcast. That's a product I don't think I've EVER seen warped. Finding something to lay down over clear acrylic without bumps, swarf, or other imperfections could be tricky.

[Dan Hintz]

You could try a polyester-based vinyl, though rastering may not give you a clean engraving without a lot of post work. Maybe you should consider a thin (<1/32") sheet of black acrylic glued to a thicker clear piece... raster away the black acrylic. At those thicknesses, though, you're likely back to some form of vinyl or acetate.

[Joe Hillmann]

It won't be cheap, but you could look into hiring out the painting. I would assume most auto body shops that do painting would have the ability,equipment and know how to do a good enough job of painting to meet your requirements.

[Rodne Gold]

Use a thicker paint.

[Rolf Randby]

Have you tried black vinyl lettering plastic? I'm pretty sure it is 100% opaque. Any sign shop should be able to supply you with enough scraps to check it out. While you are there yet them to show you how to apply it without creating bubbles.

[Paul Phillips]

Matt, sounds like your'e getting "fisheye", small spots of oil or contaminates in the paint or on the surface of your material, if you have the capability to spray your own paint,( ie. compressor and spray gun), I would recommend some bulletin enamel such as 1-shot, and some "fisheye" remover which you should be able to get from most autobody shops. If you have your own sprayer you can adjust the amount of paint you lay down, however putting on a heavier coat is not always the best as it takes longer to dry, sometimes several light coats will give the best results. I would try and experiment with what works best.
Paul

[Matt Davis]

While I do have the capability to mix my own paint and spray with a gun, I prefer the convenience of using the rattle cans. However, that might be my only alternative if I don't find another answer. I really had high hopes for the Colorcast material, as I would have been able to eliminate the painting process altogether. The time, effort, and paint savings would have made the extra expense worth it to me. I sent Rowmark an email today regarding my experience with the Colorcast acrylic. They replied that they would look their stock over and get back with me tomorrow.....

[Rodne Gold]

Spray multiple thin coats - we find the rattle cans coverage too thin and use a barely diluted Duco car paint which is quite thick , a roller and /or brush for application works real well.