A bit of all of that. The body was sprayed with a filler primer which absorbs moisture unless overcoated quickly. All cars that I have painted so far have shown that the damage is in that layer. The moisture expands with temperature increases, until eventually it bursts through the paint which likely hasn't been well maintained. That allows more moisture to pass into the primer filler layer, making the issue worse.spegru wrote: ↑Mon Jun 04, 2018 9:36 amI've seen quite a bit of talk about paint microblistering (presumably that is what my photo shows) in Reliants but never on any of the other fibreglass cars I've had. So is this something to do with being ~40yrs old, something specific to the paint Reliant used or perhaps poor prep at the factory?
Current thinking for rectification is back to gel coat, then epoxy primer straight away. Repair and make good as required then finish off with a couple more coats of epoxy. Topcoat of your choice, the epoxy is inert and will not react with anything.