:Anyone out there have ideas, tips, on how to repair reverse-painted dial glass. Thanks.
I've tried a number of times to repair flaking paint on reverse painted dial scales, and to do it right is not an easy undertaking. The three most significant issues are 1) stopping the degradation of the original material, 2) choosing a replacement paint that doesn't destroy what original areas it touches, and 3) matching the colors so that the repair is not obvious. Then there's the issue of matching what is missing. What follows is the way I've successfully dealt with the problem and then a shorter, computer-based method that works fairly well that I'll describe afterward.
1. To stop the further degradation of the paint, you must either re-adhere the original "paint" to the glass, or try to coat it with a new layer to stabilize it from behind. You first need to determine what kind of material is on the glasss. Test on an unseen portion of the dial to make all these determinations. The "paint" could be screen printed lacquer or it could be a decal film that was floated onto the surface of the glass where it dried, just like the decals on the models we all used to build. If this is the case, you may be able to re-wet the decal and see if you can reposition any flaked portions. If it's lacquer-based paint, make sure that there isn't any dirt behind the loose paint and spray several very thin coats of clear lacquer on the back of the paint. If it doesn't dissolve the remaining paint into a puddle (always test in an unseen area first!), then this usually causes the loose pieces to bond to those next to them. If the flaking portions do not "lay down" on the glass, you may need to "encourage" them to lie flat before they dry using a fine artists brush.
This method should stop the dial from degrading further.
2. The main concern in replacement paint choice is the potential disruption to the original paint it borders. The layer of lacquer should help prevent this, and if you can match it well, acrylic paints should be flexible enough to accomodate the different expansion properties of the lacquer. Of course, lacquer paints are a great choice too, although they may be a bit tougher to work with and will try to dissolve the layers beneath them. I can't really vouch for how well the acrylics holds up under the heat produced from the chassis, since I haven't subjected any of my repairs to that torture (which is somewhat responsible for the original flaking). Perhaps someone else can verify how well this kind of repair holds up under heat.
3. I find color matching to be easiest with artist acrylics, which can be found at any craft store. Just blend them until they are a reasonable match. Remember that you'll be looking at the back side of what you're painting, so it can be helpful to make a test strip out of a clear material (I use plastic wrap) to get a better idea of the way the color appears through a clear medium. Start your painting in layers from items in the foreground (numbers, labels, etc.) backward to the background. This is tedious work, and explains why sign painters charge what they do. I've found that for the letters and numbers, putting on a bit more paint than I want makes it easy to take an Exacto knife and make the edges sharp. Don't let the paint blob at the end of your strokes, since they are backlit and that'll show through as darker patches or streaks. Once a layer is throughoughly dry, you can add the next layer, until you are ready to either spray or VERY carefully apply the background colors. This is bery difficult to do with a brush without streaking, so I use a little airbrush kit from the hardware store ($10). You'll need to mask off the clear areas while you do this. I use a vinyl electrical tape that removes easily, but have also had good luck with blue, easy release masking tape.
An easier method if you're in a hurry or not feeling particulary artistic, is to use a color photo printer and a digital image of the dial glass. Use the retouching tools in a program like Photoshop to fill in the missing portions of your dial using the cloning tool, etc. When you're satisfied, print the result on the clearest overhead transparency material you can find. If you've adjusted the size correctly, you can position and secure it behind the original dial and let that suffice for your repair. If you want to be more adventurous, you can digitally remove the portions of paint that remained on the original dial and then carefully match up your new portions with the original.
As a final note, please make sure that you don't accidentally destroy you original dial. Test the original paint in an unseen spot to make sure what you are adding to the dial will not cause more problems than it solves. 'nuff said. Good luck!
Doc
:http://www.radiodaze.com/ has reproduction dial glass. Check out their reproduction items section. It might be easier if they stock the one for your radio.
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::Anyone out there have ideas, tips, on how to repair reverse-painted dial glass. Thanks.