sweaty resin.

[Blindhorizon]

So a piece i'm trying to cast has came out sweaty twice. By sweaty I mean, shiny and slick to the touch even after washing with soap water and a toothbrush.

Is this because of the mould, or did i not mix the resin enough? Which is odd because i cast other pieces on the same pour and they are fine.

With sweaty pieces will primer stick to them or are they a total waste?

Blind-

[mangozac]

I wouldn't bother trying to use them. You may get the primer to take for the time being, but it may just peel off again in the future.

I believe it's from not mixing the resin properly. Just because the rest of the casts from that mix are OK means nothing: it may have been just one area of the cup that didn't mix when you were stirring, which made itself into just one part. Always mix for a little longer than you think you need to!

[Blindhorizon]

Thanks mango!

[Fleafa]

I have had this from incorrect ratios and old, cheap resin. Poor mixing could do it.
I measure with a syringe and mix in a cup. I then pour it between two cups a few times.

[Pinselknecht]

Because your other casts are good I belive in wrong mixing or mixing ratio!
Biggest problem are the resin mixed by volume, that is not correct!
Always mix by weight!!!

[Fleafa]

[Pinselknecht]

Yes, but I never got any professional resin with mixing by volume. These resins are made for hobby use or from smooth on! Professional ones are always by weight to be able to add filler or other additives.

Mixing by volume is never prezise, it has a leak of minimum 3-5 % just by the concave survace of the resin, and you never have the survace in level!

This leak means a big effect on the resin itself and its hardening prozess!

The same problem ocure if you have the wrong mixing beaker with no flat bottom. You have one part traped on the bottom and this part is going into the rest of at the pouring process!

[Fleafa]

Fair point. I'm using Smooth-On, making small batches, and measure with 2 60ml syringes. The margin of error is small enough that I never have this problem. I use cups with no flat bottom, but pour several times between two, which eliminates that problem.
I doubt most people here won't be able to buy in the volume required to get pro resins.