looks like you didn't seal the primer before you painted over it on the fiberglass. Filler primer needs a cover coat before you paint over it. You didn't get the same issue with the aluminum because you used etch primer. Chemicals from the paint leeched into the primer and softened it. I've never run across your problem so this is an educated estimate.
How come you didn't seal the polyester primer? Should always put a barrier between the topcoat and bottom coat when dealing with polyester, its nothing more than liquid body filler.
Like most of the painters have said--too much material. It's easy to give those door tops an extra pass each time (coat) around the car. I'm also suspecting the base white-801J tint-. Did you use straight mixing base white (801J)? Those tints need 1 or 2 additives to make them dry properly. Straight mixing base will stay gummy without addatives (balancer-binder-drier) mixed with them. The white mixing base has a lot of mineral (titanium dioxide) in it which traps or holds solvent between the larger pigment molecules. That will add to the effect you have. If you shot straight mixing base without addatives, it may not be very durable and the paint film will fail much sooner than it should. You might have to strip it off down to the primer. I'll check with the local Dupont guys and see what should be mixed with 801J for spraying it by itself. Or, anybody have a mixing machine on here that can see what the binder and balancer numbers are for either single stage or basecoat? overspray
Yup. That and the extra material applied in the areas (door tops) that have this effect. A trip to the local Dupont jobber confirms that the 801J master tint white mixing base needs to have a binder and or balancer to make it dry and stable. The local jobber also said that when using the master tint as a basecoat, you should put the reccommended hardner in the basecoat which is critical to prevent delamination of the clear coat. 801J tint cannot be sprayed with just reducer or basemaker. Double check and see if the binder was in the mixing formula. These tints are like most of the european style paints which use 1 set of color tints to make both single stage and basecoat color formulas by adding different binders and balancers. overspray
I'm with several of the guys here it's the primer and not your methods. I used two different primers one time and had the same problem. Wipe the whole thing down and redid it over with the same primer after a long trip to the store and everything went fine. The best bit is to always use the same brand, same primer, same base coat and the same clear, it's the safest way. CRUISER
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