This has to be a bit hurried, as I’m so, so tired…

After a week of experiments, I’ve produced my best cast yet, and it was partly down to a surprising find along the way. No, it’s not what I consider to be perfect, but I fixed the problem of the mould not filling all the way. Anyway, here’s the story of that find:

Into the spidery shed

The springform cake tin was a great idea for keeping hold of a round mould, but RTV silicone doesn’t like to be cast on its side – it won’t vent steam like oil bonded sand will, so it just forms mega bubbles, even with an incline. It has to be vertical.

That meant that I had to clamp it in place vertically and apply pressure on the sides to keep the mould tightly in place, or else all my pewter would just dump out into the bottom of the cake tin.

I was trying to come up with some system for jerryrigging a clamp – maybe a car jack wedged into a box? – and got Ste on board to excavate a box from our spider-riddled shed. As the spider-spotting backup, I was peering into the dim wooden cavern when I spotted a box we hadn’t seen before.

It was an unopened clamping table!

The exact model isn’t made any more, but this is the closest version.

The previous owners had obviously abandoned it to the eight-legged shed denizens, and somehow I’d never seen it before.

Although the nuts, bolts and plastic pieces were still sealed in their plastic bags, there was a fair bit of corrosion and that dank shed smell. Still, I put it all together the same day. It needs a bit of oiling and messing around with to help it fold up, but set up, it’s just right for the job.

I can’t believe that I just happened to find the exact thing I needed! I couldn’t have done the casting without it.

Tips for pewter casting

I’ll have to write this up as a separate post, of course, but here are this week’s discoveries:

• Fill from below. When you pour hot metal into a mould, you create turbulence in the flow of the metal – steam, bubbles, slag, all rolling around. You need to cut this out, and to do this, you need to fill your mould from the bottom up. This means having a separate pouring spout that feeds your mould from below.
• Use a tapered sprue. This helps to reduce turbulence as well, controlling the flow of the metal.
• Make your sprue big enough. The metal may freeze before filling the mould if you don’t.
• Plan your sprue and gating system into the mould making process. I didn’t do this… I did rely on the fact that I could cut the silicone afterwards, which is less than ideal, and means that I’ve had to patch some bits with oil-bonded sand.
• Wax acts as a flux, but don’t add too much. Pretty self-explanatory.

Now that I’ve achieved this week’s goal, I’m going to carry on with another job: helping my husband create some of his own moulds. I’m refining my DIY silicone mould-making technique and scoring major brownie points at the same time!

Last week

Next week

I got that push to finish and publish my second journal, and do you know why? Because I made a massive mistake with casting my coin and had to do something with myself while I was waiting for more silicone to arrive.

It seems as though I’m mostly reporting on huge failures, doesn’t it? Well, that’s what it feels like to me sometimes!

Still, at least I have enough to get on with to fill in the gaps when things don’t go perfectly.

Mould making, the right way

Confession time – I know how to make two-part moulds, and I know how to make even more complex, multiple-part moulds. I’ve been doing mouldmaking for 20 years now, so I have a handle on the basics… so what the heck is up with my recent run of catastophes?

The simple answer is that the silicone I’ve been using has given me the option of being lazy, and faced with that option, I’ve grabbed at it with both hands like a desperate woman.

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Just opened up the mould – time to clean it up and cut the pouring channels. . . #pewtercasting #coinart #moneyart #mouldmaking #siliconecasting #moldmaking #fineart #art #sculpture #rtvsilicone #metalcasting #sculptor

A post shared by Lee Devonish (@lee_devonish) on Jul 5, 2019 at 2:22am PDT

Why lazy? Well, you can cast a solid block and then cut it apart, unlike with plaster. Working that way around, what happened was that my pouring spout was too narrow to accommodate an adequate flow of silicone, so with an 8 minute pouring time, I ended up with a lot of silicone that had gone off before I could use it.

Fast forward a few days and another batch of silicone, and I made the mould the right way. Don’t be lazy, kids.

Prepping for a new casting project

I’m not just working on the coin, though. I’ve got a plan for my soap base in mind, and my poor plastic artist’s assistant is getting roped in as a model.

Right now I have to pull up the handbrake on work though, as the studio contents have spilled over (in some cases, literally) to the rest of the house and I have to scoop up all of the leftover silicone that’s been chipped up for recycling and clean off all of the wax I tipped over the cooker and the kitchen floor yesterday…

Will I get to cast the pewter next week? Maybe, but maybe I’ll work on prepping the rest of the things I want to cast at the same time. We’re looking at getting or making a casting flask for sand casting, so I may work on that instead.

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