What makes clearcoat yellow like this?

[dantewallace]

I built this back in 1995 and over the years the clear coat has turned yellow. The car was always stored in a climate controlled environment and I want to say that the clear used was Testors. Anyway,is this some sort of fluke that happened by having bad clear or is it the fact that I used to much clear? In the pics you can see that most of the yellowing is in the spots where the clear pooled up,but the yellowing also exists over most of the car in the thin spots. How can I prevent this from happening to future builds? My skills have immensely improved since this build and I would hate for my previous work to meet the same fate in the next 20 years or so.

[my name is nobody]

what make's clear coat yellow like that?

TIME.

after a few years, cheaper clear coats and even some of the

more expensive brands tend to yellow out.

with the exception I've found, of Tamiya clear.

[Blown03SVT]

The enamels I have used will do that, only noticeable on lighter colors usually. Laquer clears (which I beleive Tamiya is a laquer formulated for plastic) tend not to yellow like that.

[Guest]

With the visible pools of clear, you definitely have too much clear on it. There's no way to keep Testors enamel clear from yellowing over time. Every single build I have with Testors clear on it has yellowed in varying degrees. You can either switch to lacquer paints and clear or simply polish your paint.

[dantewallace]

About four years ago I switched over to Model Master Ultra gloss clear and love the results I get from it. How safe will I be using this in terms of longevity?

[Ace-Garageguy]

Back in the dim recesses of history ('50's-'70's), clear lacquer for 1:1 cars would yellow over time as a result of the effects of ultraviolet in sunlight. Whites were bad too, as well as light gel-coats for fiberglass. As UV inhibitors were developed and added to clears and gel coats over the years, the problem has diminished.

I don't know if model-car clears bother with UV inhibitors. If not, even in a shady room, you can probably expect at least some yellowing over time. A model doesn't have to be in direct sun for it to happen...I've seen the undersides of glider wings that were badly yellowed (you could see the original white when the numbers were removed) even though they had been either shaded or stored in closed trailers for all their lives.

[VW Dave]

the clear used was Testors.

There's your answer.

I did a '65 Shelby back in the mid 1980s, and it became kinda amber-colored over time because I cleared over the Testors white enamel with Testors clear. When I re-did it in the late 1990s, I used straight Model Master white with no clear, and it's still white today.

[Swamp Dog]

most clear coats all ready have a yellowish tint to it..testors being # 1..