Decals - When are they too old to use without pretreating them?

[Miatatom]

Some of the kits I've accumulated are pretty old with yellowed decals. I know they'll bleach out when exposed to direct sunlight. I've heard of spraying them with clear. What do you use, lacquer or enamel or Future? Is Micro Industries decal film better? Opinions?

[jbwelda]

in my experience, all those things you mention will work. I think though that lacquer clear might be too fragile to cut apart, but I have used future to good effect and also the micro ind film stuff. I don't think its a matter of age either, I have had relatively recent decals break into a million shreds on contact with water, and ive had old decals that had yellowed but still held together fine. I pretty much try to test first with an insignificant decal if possible.

jb

[Art Anderson]

Numerous times, in my years of concentration on building models of Indy cars, I simply airbrushed a coat of clear lacquer (back then, after AMT dropped their line of spray lacquers and before Tamiya and Testors introduced theirs') on any sheet of decals that worried me that they might break or crack. I simply used clear automotive acrylic lacquer, appropriately thinned for airbrushing.

It's been my observation that decals crack for two major reasons: First (and this happens in production at times) the clear lacquer that most decals are printed on didn't get applied to the decal paper before the colors were printed on. It's that layer of clear lacquer that has the strength, not the printed ink for the graphics. Second, with old decals, given that decal paper is simply thin blotting paper, coated with a layer of gelatin (which is water soluble and sticky as it dries), the decal paper can absorb water simply from the moisture in the air, which will cause the paper to curl up (or at least try to), and once it's dried again, any attempt to flatten it out can cause the clear lacquer decal film to simply crack apart.

Spraying a light coat of clear lacquer over a decal sheet in advance, particularyly if one has any concern whatsoever about the integrity of that sheet of decals, has always worked for me--and in the end result, the treated decals have laid down just fine for me, even reacting well with setting solutions.

Art

[Miatatom]

Thanks Art, for that answer.