Ok so it seems it was the reduced viscosity at higher temperatures. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Problems are gone when working at 20-21C.

I've made a mistake when writing first post. It appears I've been sanding with 150 and 220 foam backed sandpaper and not 220 and 400 as stated in the first post.

Thanks guys. Explanations seem logical.

Yeh it's really too finely finished. Finish with 180 grit at the finest before applying your final coats of resin.

It could be the surface needs more keying to give better adhesion.  

Also 25C may be a little too warm.  Although ideal for curing, the resin does thin out a lot above 20C which ironically would make fisheyeing worse so often working closer to 20C helps prevent this happening.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

EDIT: I've used 150 and 220 foam backed sandpaper in step 5.

All work is done at 25C
I'm skinning some parts with XCR. Process is as follows:
1. Basecoat. 
2. I put carbon after basecoat reaches B-stage.
3. Everything goes into vacuum bag @ 20-30% vacuum overnight.
4. I put 3 coats of clear with 1h 30 min intervals as instructed in XCR datasheet
5. After 24 hours at room temp, and 8 hours at 60-70C in the oven I dry sand with 220 and 400 grit, wash off the dust, dry, degrease the surface.
6. Two more coats of clear resin similar as in (4)

Now the surface after two last coats has many craters. Is this called fish eyes?


How to prevent them? Last time I've tried acetone, silicone remover, and IPA alcohol on three different pieces before last two coats. All 3 pieces have exactly the same defects.