James Nelson wrote:
>
> ...Smooth Prime says you must use the "paint mfg. primer
> with their paint." If you use Polyfibers paint, you must
> still use a primer on top of the smooth prime and then follow
> up with a color coat.
PolyFiber's paint book says you may use solvent-borne primers over
smooth prime, but that it is "overkill." Has their advice changed? I
can't see how they can imply that any brand of primer will adhere to
Smooth Prime better than any brand of topcoat alone. Their
water-borne coating competitor has contrary advice here.
Besides weight, excess total coating thickness can be a real problem,
and has happened to me. It's described in Sherwin-Williams'
Troubleshooting Refinish Problems, under cracking and peeling. I
noticed it especially on fiberglass parts of a metal airplane, as I
suspect it may be the varying expansion coefficients in mixing
finishing systems, especially on flexible surfaces like fiberglass.
Further aggravated by frequent temp extremes. And especially with
hard polyurethanes, which if hard don't stretch either, so in a few
years it can just fall off if it doesn't do you a favor and merely
crack. That's maybe why PolyFiber says their solvent poly is super
flexible, appropriate for fiberglass too, and is applied over Smooth
Prime.
Regards,
Fred F.
N3EU
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