I have attempted to cast a model using Easy Composites' Fast Cast Polyurethane Casting Resin. The cast failed as the resin did not fully cure. Half the model cured but the rest came out like thick honey, see image above. I'm not sure why this happened, but my immediate problem is, how do I clean the uncured resin goo from my mold? The mold is made of RTV silicone.

How long did you cure and at which temperature? 

I opened the mold after an hour at room temp.
I did a previous test the day before, on that occaision the resin had began to cure within minutes of being mixed, and I was unable to finish pouring it before it had begun to cure.
I weigh the resin in two seperate containers to make sure I get the 50/50 solution, before mixing them together.

It's very rare that fast cast won't cure at all unless the mixing ratio is well out.

What looks like has happened here is that your quite thick moulding has absorbed some of the heat used to exotherm the cure hence its not cured.

I would apply some heat in an oven for a few hours to force a cure.  If it still doesnt cure then something has gone seriously wrong with the resin. 

Acetone would be the best method to clean off the liquid goo if you cant get it to cure.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi Warren

The residue in my pouring container didn't harden either. I suspect the resin was badly mixed, in that Part A probably wasn't shaken. I don't know how big a difference that might make but in all the containers I bought from Easy Composities, the Part A appears to be seperated into a thick residue at the bottom, and a thin liquid on top. I did two tests prior to my casting efforts. The first ended up much as this cast has done, a thick honey like sludge. The second, when I shook the Part A for a longer period of time, cured very rapidly.

My first cast attempt was also a failure as the resin cured so fast, I never managed to get more than 10% of my mold filled (this is my first ever mold).

I've clean the mold now, using acetone as advised, and it appears to have worked. I'll try for a third time (when my children aren't taking up all my time) and post the results.

It seems like it is a big part to cast... The reason why it cures so fast is that you probably make big batches of resin at the time...

I think the answer is simple, he has already explained that he did not mix the separate parts before mixing them together, so he was skimming the top off a part, which cured fast, and the sludge went into the second, which hardly cured.

Get new resin, shake/stir the individual containers, and then mix correctly 50/50.

A friend mixes this on large scale, 30kg containers, and he stirs part A + B separately with a drill and stirring attachment.

cheers

You definitely need to shake the fast cast tubs to ensure they are properly mixed.

There isnt much you can do to slow the cure down really, other than work in smaller sections or work in a colder environment initially.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I mixed 170 grammes in total. I don't know if thats a big mix or not, as these are my first attempts at resin casting