I agree with Oekmont, that really cant be the issue... it has to be a coincidence. 

I highly doubt your interpretation. Epoxy doesn't really care about whats underneath. The bonding strength might be an issue, but the hardening should not be a problem.
If you are 100% shure about your mixing ratio, I would look at your scale, and the surface you are weighing on.

Seems I found an issue . Main difference between that coatings in spring was that it was on laminate of the same (XCR) resin. These past few times it was on laminate of EL2 resin. I thought that your EL2 resin will be compatible with XCR. It seems that not completely. I've experienced similar issues last year when XCR stayed not cured on MGS285 resin. It stayed very sticky for a very long time ( 3 weeks ). Then I tried to scrub and wash it.  I saw that XCR is very sensitive to what lays underneath. So I decided to switch to EL2. Finally see that it does not work also. I loved all XCR properties except of that sensitivity. It's sad but I'm starting to look for another system.

I've got 1kg new batch XCR resin on Monday. Tried to sand it dry after  70 hours. Result is better but still insufficient. It clogs 180 and 240 grit sanding net. Resin is glossy, but if I  hold warm finger on it for 10-15 sec, it feels a bit sticky. Working temp. 21C, humidity <50, curing temp.22-23C. It did not act in such way when working in winter/spring time. What variables else could I change ? Try to change scales ? Loosing my will to work with XCR

I meant when you mix up a batch to use, eg 50g, 100g etc.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

What sort of batch size are you using?

Mixing or measuring errors effect different resins differently depending how sensitive they are.  Some resins you can get away with being less accurate but still get a good cure.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

My scales are 0,1 gram precision and I'm always mixing very ( very x 3 ) carefully.
I'll do some hotcoat on Monday. This time with new batch resin. Result will explain everything. Because there not so many variables left . So I'm looking forward impatiently to result
By the way : if there would be scaling or mixing problem, that definitely affect other resin ( like laminating resin EL2 ). But latter cures and sands perfect.

A light tack would suggest that the resin hasn't fully cured properly for some reason, be it a mixing or measuring issue or some kind of contaminant inhibiiing the cure.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant