Wednesday, September 20, 2017

Getting primer to stick to resin

A while back I described problems I ran into as a result of not knowing about mold-release agents used in resins (here). Atthat time, a bit of research led to the conclusion that a good cleaning in 99% isopropyl alcohol (propanol or rubbing alcohol) followed by dish soap in hot water would do the trick, and indeed I haven't had any problems since, especially when the alcohol bath includes a vigorous scrubbing with a sacrificial toothbrush.

With the current '51 Belair wagon resin body, I ran into some problems with the paint.

I cleaned the body up with isopropyl alcohol as I have done in the past. Then I applied a couple of coats of DupliColor primer/sealer, with no issues around bubbling or any of the other problems associated with applying primer to a resin body which is coated in mold release agent. Finally I put on a couple of coats of Krylon top coat as detailed in recent posts, again with no problems attributable to release agents (although the problems related to using a rattle can were on hand as always).

The problems arose when I started scribing around where the wood-colored paint will go, and was surprised to see the entire paint structure, right down to the primer, lifting off in sheets like multiple layers of old wallpaper. Clearly the primer didn't really stick to the resin. 

So what am I missing? The primer was on for over a week, the top coats for several days, and there has been plenty of time for it all to set. 

Several members of the Facebook group "Model How To's" recommended soaking new resin parts in Wesley's White Wall Cleaner or Black Magic Bleche-Wite tire cleaner. These contain a mixture of an alkaline chemical and alcohol, so presumably they are a more aggressive version of the propanol I have been using. For now I've repaired the flaking bits by carefully trimming with a fresh X-Acto blade dragged along a crease in the body where the step change in paint thickness won't show. 

Then I painted the two wood-coloured portions of the bodywork and some of the chrome parts. The photos show a bit of sloppiness (this is all brush work without tape, so actually it is all pretty good), which will be tidied up; the rest of the chrome will be with Bare Metal Foil. 

Stay tuned -- I will update both the resin cleanup story and progress on the tin woodie Belair. Remember to use the bar across the top of the blog to select Tools & Tips to find this and other posts that are not directly related to specific builds but to generic problem solving approaches.

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