Casting Cthulhu

I’ve been asked a few times over the last couple of weeks how I actually mould and cast my statues. So rather than do a project update blog, I’m going to talk a little about how I cast my statues using (appropriately enough) a brass Cthulhu that I cast last weekend.

Before I actually start yammering, I’m going to do another quick link to my Facebook page Castings of Cthulhu and remind you that I’ll be posting updates and random stuff on there on a more regular basis. I’ll be using the blog for posting finished projects and bigger updates.

Ok, shameless self promotion done, lets move on…

When I first cast something many years ago in art college, I used plaster which was messy and not very good for details and then moved onto Vinamold at uni. Vinamold is a rubbery material you heat up and smells vaguely of chicken soup (as I remember) and is reusable so it has some good points if you like chicken soup. Skipping on 15+ years takes us to the point where I hadn’t cast anything in ages but wanted to start casting my Cthulhu. After a wander around the local craft shop I left with a big bottle of latex and a small bottle of latex thickener. This was for the very first Cthulhu mould and I spent a couple of weeks layering latex over the original.

The first few castings where pretty disastrous as I attempted to figure out what the hell I was doing, to the point of dumping £30 worth of bronze powder into the mould with a load of resin and it going horribly wrong. It was a bit of a downer but I’ve slowly managed to refine my technique over the last few years. Not to say everything comes out perfect, but every casting helps me figure out new things and I get it right more often than not now.

From left to right we have the first mould in latex, the second mould also in latex, the third mould in Dragon Skin and the fourth (and current mould) in erm… Dragon skin as well. I think. Probably. Pretty sure it is anyway. There is one missing between two and three which was from a private commission for a Cthulhu in a green stone effect. I tried to use a material with stone in it which pretty much thrashed the mould but I think it was a cockup on my part more than the materials used. I think I miss calculated the ratio of resin to stone and it ended up a slightly crumbly Cthulhu. I just binned the mould in the end as the inside was shredded.

This is the insides of the Cthulhu latex mould.

Cthulhu Dragon skin mould.

and the other one which is probably Dragon Skin. I’m 99% sure its Dragon Skin… well… 95%.

The original latex moulds are still in pretty good shape. The first one has a couple of rips starting to appear as one downside with latex is how little it stretches. Don’t get me wrong, its rubber, it bends and flexes but when you’re trying to peel a skin tight rubber mould from a statue of a great old one, you want something that has a little give in it. A few times I came close to just cutting the moulds and being done with as my fingers would be hurting and I’d be sweating trying to get it off the damn casting. So I did some reading and ended up getting some of Dragon Skin FX-Pro from Bentley. This stuff is wonderful and I now swear by it for my one piece jacket moulds (I’m mainly using Oomoo for my two part moulds and thats also by Smooth-On).

The whitish clear mould was made in a weekend and I made the mistake of not using any pigment in the material which meant it was hard to see where I had applied it, hence why the fourth mould is coloured. Its much easier to see where its been layered on. Dragon skin is applied in layers, like latex, but where latex takes a day or so to dry (the ammonia evaporating) this stuff can be layered up in 45-60 minutes before its fully set. Meaning most moulds can be made in a day and dragon skin stretches like you wouldn’t believe. You can pull it 200%+ of the original item so demoulding is much easier.

So once the mould is done, its time to fill it with something. I’ll just backtrack a small amount and add something about mother moulds. Smallish items can be cast as they are in the mould but bigger items need a mother mould around the main mould to hold its shape. Mother moulds are rigid outer shells that support that floppy inner mould as when you fill the mould, it will sag and bend unless it has something to hold it in place. I’m currently using Plastipaste for most of my mother moulds (it’s by Smooth-On, spotting a pattern yet?) and comes out looking a bit like expanding spray foam only rock hard.

OK, so we have our mould and its snuggled up inside the mother mould, its time to fill it with something. Well, not just yet. Spraying the inside of the mould with some form of release spray is useful at this point.

I’m not going to point out what make my current spray release is, suffice to say that I get it from Bentley Materials where I get my moulding materials from.

A light spray inside the mould and inside the moulding cups. Yup, it helps to recycle the measuring cups when the resin has set as you can pop the waste resin out and save it for later. While its not vital to have a release spray for moulds, it does help to save on wear and tear.

OK, now we can fill it with something. This is Easy Flow clear…

…and this is brass powder in the Easy Flow Clear.

Depending on the casting, I put a specific amount of part A in one cup and the same amount of part B in another cup and then mix the same volume of metal into each cup, mix them up in the cup and then mix the two cups together. Odins, Freyjas and Thors all use the same volumes while Cthulhu takes a much larger amount. Easy Flow sets fast so after mixing together its time to pour it into the mould and roll that thing around to make sure every part of it is coated. I have experimented with just dusting the insides of moulds with metal powder and then pouring the resin in but I’ve never had satisfactory results to be honest.

So now we have a thin layer of Easy Flow and metal powder glooping around coating the insides and after about five minutes the Easy Flow is set enough to leave to fully cure.

We now have to fill the void. Remember that mould release we sprayed into the cups? Once the Easy Flow has set we can pull the bit thats set at the bottom out and drop it into the gap along with any other materials we have to hand to help back fill the hole.

This is Polycraft 7450 that I get from mbfg.co.uk and is a nice cheap back fill resin that I mix with black dye and either Aluminium Trihydrate or Fillite to help bulk out the resin. When I first started to cast these I was using Marine grade fibreglass resin as I could get it cheaply, but the stench meant I had to do them outside and also they got really really hot when curing. The volume of resin poured into the hollow Cthulhu meant there was often jets of steam coming off them and the rubber got really dark from heating up. Even filling in stages didn’t help a lot so I quickly shifted onto stuff with no smell (everything I use these days is pretty much odourless) and doesn’t get too warm.

Backfilling helps to keep the production cost down as well as the weight for shipping. If I was to fill with either solid resin or anything else then the shipping costs would go through the roof. Anything over 2kg is a shocking price to send signed for overseas from the UK, so in the interest of actually being able to stock Cthulhu at a price that people would be willing to pay for shipping, I try to keep the weight down.

Demoulded the castings look quite dull, so it’s time to hit them up with some metal polish and fine grade wire wool. The outer layer of the casting has a layer of resin which needs to be removed. I use firegrate polish on my casting to help age them and brush them all over with the stuff before buffing with wire wool then buffing with a cloth and the difference is noticeable. Firegrate polish has a high percentage of graphite in which helps to darken down the casting and also sinks into the deeper recesses of the casting giving it an appearance of aged metal. You can mix raw graphite powder into the metal powder at the casting stage but it has to be worked out carefully or else you end up with a very dark finish.

Once the polishing is done I base the Cthulhu with felt to save them from scuffing whatever surface they end up on. One early customer ordered one for his garden so I skipped the felt on that one.

So thats pretty much it. It’s a very broad overview with warts and all and isn’t intended to be an in-depth guide, but if anyone has questions then please ask away in the comments below or on Facebook and I’ll do my best to answer them.