Hey all. long while since i posted.

well i have decided to get on with my small MTB. how ever things are not going so well. I applies a coat of filler primmer and sanded it down. Which got rid of the majority of small imperfections.
So i decided toapply one more coat which i have done today.
only problem is. that the primer has started to crack and split. It has split right down to the layer of pain below the filler primers.

The most annoyihg thing is that it was almost ready for top coats.but now i have to start again and try and fill the cracks.

Anyone any idea's why this has happened and how it can be prevented in furture.

sounds like you might have applied the primer too thick if you don't thin it down enough or properly then the pigments will seperate when the primr dries . so this time try to aplly more coats but make them thinner instead of a few thick coats. hope it helped

"It has split down to the layer of paint below". Does this mean you are repainting a surface that still has old paint under the primer?

Are you applying lacquer primer over enamel?

A good way to see all the imperfections in the surface is to spray a light coat of a contrasting color over the primer. Black over red for example. As you sand the surface the imperfections will show up well because they will still be low.

Sounds like your filler hadn't cured completely. Try leaving it longer to cure before priming it (like a couple of days). The thicker the filler, the long it should cure. Good luck, Fatboy

there was no filler underneath. its is a filler rpimer. so it is naturally think. and all the coats of paint on there are all acrylic. i only use acrylic as these will paint over anything.,

Hello -thing-, Sorry to hear about your finishing problems. I hope you figure it out and show us some pictures when you get a chance to. Good luck with it.
Bill

i shall once i have taken all the filler primer back off. lol

"Crazing" typically occurs when you have two incompatable paints, or you have paint not completely cured and have painted over it. In the first case, the paint bases attack each other. The second case, the paint coats begin to dry at different rates, and it literally pulls the finsh apart.

i guess that is actually a posibility. as i sprayed some on, then touched it up. which means as u say, that they would dry and different rates.

However it is all sanded down now. and we shall see wot happens this time

ok. more panting problems now. And i really dunno why this is always during the painting process. I have a speedboat which is a plastic vacumn formed hull.

the problem is this. at the front of the hull on the final coat the paint as wot appears to be very fine bubbles.

the first coat was of hycote acrylic filler primer. then sanded and another coat of this filler primer.

then final coat was of hycote metallic acrylic paint.

anyone any idea's. i cleaned off al dust after priming using a spirit soaked cloth.