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Blistering paint on diecast models

Q: I have a diecast model car collection that I've been building for years, and recently I've noticed a troubling problem: small bumps and blisters in the paint that ultimately ruin the models. So far, two Franklin Mint, a Danbury Mint, and an AMT/Ertl model have been affected by these strange occurrences. The models are kept in glass cases without artificial lights, aren't exposed to sunlight, and are rarely handled. Please give me some suggestions; considering the price of "mint" models, I can't afford for this to happen.

- Mia Bevacqua
Monterey, Calif.

KEN: That's a new one to me, Mia. To get to the bottom of the problem, I called on a few experts in the paint and diecast fields, starting with my mentor and former "Tips and Tech" guru Pat Covert:

Pat Covert: The only way I could explain it would be the climate where Mia lives. Salt water in the air could be causing the corrosion. Has anything been applied to the paint (such as a wax or compound) that might affect the paint and metal underneath? Since it's happening to several brands of diecasts, there must be a generic cause. Bob Downie, an industrial designer and diecast collector, may be able to offer some suggestions.

Bob Downie: This has been a problem with some of the "mint" cars. I originally heard about it from the message board at Over time, there's something under the paint that can cause this to happen. It's probably something in the metal that's leaching to the surface. I looked at a few of my diecasts, and some are doing this too, but not badly enough for me to worry. Mia should check to see if the mints have any way to replace the models. George Bojaciuk probably knows what the problem is, since he worked at Franklin Mint
and is working with GMP now.

George Bojaciuk: This is common with many older issues of Franklin Mint cars. It appears that the Zamak-alloy wasn't completely cleaned, and it reacted with the paint, especially on the maroon 1941 Lincolns. Sometimes it's oxidation of certain metals in the Zamak. Unfortunately, there isn't too much you can do once the problem has started. In the case of Danbury, I've heard that if you bought one of their models that's still available, an inquiry to their Customer Service department should yield a positive result providing you're on file as the original owner. You may not be so lucky with the Franklin Mint; many of their cars have been retired. I don't know Ertl's policy.

Rick Hanmore once painted a concept model for me with self-etching primer under a black cover coat. It failed after a short time because the pigment in the black paint reacted with the primer. By the way, many of the newer mint models are powder-coated, then a clear coat is applied. These finishes are holding up much better.
I noticed that Mia's models are kept in a closed cabinet. Sealed display cases are great for keeping dust off models, but they don't allow air to circulate around the cars. This is pure speculation, but trapped salt air in your cabinet may be causing your models to rust, just like their 1:1 counterparts. Try cracking open the door to allow more air to flow.

I hope we've been able to at least offer some insight to your dilemma. We'd like to hear from any readers who may have experienced the same type of problem.


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