XCR resin sanding problems


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Warren (Staff)
Warren (Staff)
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waxy surface? did that come off easily?  Sounds like a bit of amine blush which could be caused by a couple of factors.


Warren Penalver
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That does not come easily, only with sandpaper. But only wet sanding possible. Or using kilometers of sandpaper. It looks like good glossy surface. But when touching it with fingers and holding finger longer, it feels a little bit sticky. And that does not come out even after two weeks of keeping in warm. Only mechanical removal is possible. Also I've noticed that covering another layer of hotcoat causes week adhesion if  that sticky layer previously is not removed but for instance only made mat.
So what factors else I should consider ?
Warren (Staff)
Warren (Staff)
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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
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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 Smile. So I'm looking forward impatiently to result Smile
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.
Warren (Staff)
Warren (Staff)
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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
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Warren (Staff) - 9/13/2018 3:12:56 PM
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.

Usually I was ordering 5 kg size. But now ordered 1 kg for testing.

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


Warren Penalver
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Warren (Staff) - 9/14/2018 8:23:23 AM
I meant when you mix up a batch to use, eg 50g, 100g etc.

Usually 100 to 250g. I was doing mixes up to 350g with XCR resin bought last year. Sanding after 24 hours was not very good, but never had problems with dry sanding after 48 hours.
This problematic resin we are talking about stays with the same soft top after 7 or 10 days. And keeping in higher temperatures doesn't help. Tried this several times.

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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 Sad
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Seems I found an issue Smile. 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.
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