Resin Peeling - slightly sticky

[Brazoo]

I just de-moulded my first resin head - and there are a few small areas on the surface that feel sticky, and it's peeling in very thin layers.

Any idea what it might be?

My first thought was a little too much releasing solution may have pooled in those areas - because everything else looks perfect, but I'd really like to hear what more experienced folks think.

[jessica]

Perhaps you did not mix the two materials evenly? Not sure what you are using, but I use a 1:1 type of resin. When I first mix the two chemicals together, it's cloudy...but I keep stirring/mixing and then I notice that it becomes ultra clear as soon as the mixture is homogeneous. Sometimes if you look closely, you can still see strings of material that are hazy and not ultra clear. I keep stirring until all of this is gone and the entire batch is ultra clear.

I also noticed that no matter what I did, one of my casts still remained tacky and sticky on the surface. I concurred that the material was too old and had to dump it.

[Brazoo]

Thanks Jessica!

I used Smooth-On Smooth-cast 300 which is a 1:1 resin.

I thought I mixed them evenly, a couple of smaller accessory parts and most of the head turned out perfect - but I see what you mean - I guess a small vein of unmixed resin could be the problem.

I guess the only thing I can do is clean out the mold and try again, this time paying even more attention to the mixture.

[gaga4toyz]

What are your molds made out of?

I've made 1000's of castings using different types of resin and different types of molds. I never use mold release. I've gotten 50 casts out of a a cheap mold and 100+ out of molds made from good material. The few times I used mold release I must not have done it right and I had casting that paint wouldn't stick to, sticky castings, and really shiny castings.

If you feel you must use a mold release, pour some baby powder in your mold. Turn the mold upside down and tap all the excess baby powder out. It works well for a mold release without leaving any residue on the castings. If you have any other questions feel free to pm me.

[Brazoo]

Thanks for the help - I really appreciate it!

I'm using Smooth-On OOMOO 30 silicon for the mold. Both the mold and resin were from a starter kit Smooth-On sells.

[renegade]

You did not mix the 2 either long enough or didn't have a 1 to 1 ratio. Also I've found that trying to make to much resin at once will cause this. I used to pour enough for 5 or 6 molds but now I stick to 2 maybe 3 molds. Try taking the sticky casts and putting them in the oven for 10 minutes at 275F then just let then sit. (oh and you dont have to use the releasing solution with oomoo)

[Boris71]

If you are using a liquid mould release, you need to be carefull I have had loads of problems when using mould release from the same company I bought the silicone from :(

what i find the best is to use a lint free rag or kitchen towel and smoot an extremely thin layer in the mould or if there are not too many small undercuts in the mould use none, it will reduce the moulds life but save the problem

[ctc]

Hmmmm....

The flaking is weird, but the stickiness happens if you didn't mix 'em enough, or if the resin is old. (Most are good for up to a year if you keep 'em tightly sealed.) I never use mold release: I powder the molds with babypowder.

Don C.

[Brazoo]

What babypowder do you guys use - talc or cornstarch - or does it matter?

[ctc]

Hmmmm....

I go talc. Unscented. The cheap stuff.

Don C.