Saturday, September 17, 2005

First Pewter Casting

Yes, at last, I managed to get all of the necessary equipment together and find time to try to cast some simple pewter medallions using an open-top mold that I carved from plaster quite a long time ago. Come see my first effort, and prepare to be duly unimpressed.

In the following picture, you see the basic requirements for casting pewter. These include a full-face protective mask, welding gloves, a pot, a ladel, a mold, some pliers, the metal itself, and a source of heat (not just the lighter, you'll see the propane burner later).

Step one of the process is to melt the pewter. For this I have a small pot which will never serve any other purpose. My bar of pewter had to be brutally downsized with a hacksaw to fit into the pot. In the image below, you can see the pewter starting to melt (I only used about two-thirds of the original bar).

It didn't take terribly long for all of the pewter in the pot to melt. I then put the ladel in the pot to warm up, so it it wouldn't be excessively cooling the pewter on the way to the mold.

Shortly thereafter I was ready to cast my first piece. My first attempt to ladel pewter smoothly onto the mold was less than stellar.

Not that I was particularly worried about getting a clean pour on my first try. I managed to get pewter in just the "target area" in future attempts. It's what the cast piece looks like that matters, anyway. Well, that didn't turn out too well either.

The important side of the finished piece looks pretty dreadful. Much of the design doesn't show up at all, and what is there doesn't have much definition. It looks like I'll need to carve a deeper, clearer design if I want to get a good piece. I cast a few more just to see if the mold needed to warm up, and they all came out about the same. Sometimes the metal bubbled mysteriously while cooling on the mold; I'm not sure what that was about, although Fjorleif and I have a hypothesis about water in the mold vaporizing and bubbling up through the pewter.

I also got a lot of debris of some sort, shown in the picture below. I got lots of it in the ladel and on the surface of the metal in the pot. I'm wondering if this is some sort of tin oxide forming on the surface of the hot metal or something else entirely. I'll have to ask around (feel free to post a comment if you know what's happening here).

That's it for my first try at casting pewter. I'll try deepening this mold and carving another one, as well, and I'll try to remember to take pictures of that part of the process, too.

EDIT: I've made a somewhat-more-successful second effort.

1 comment:

Syridian said...

Hiya, the debris you are getting is normal slag which happens in any metal casting process.. You can just scoop it out with a teaspoon if you like.

As for getting more detail in the mould, try making a 2 part mould, and when you are pouring, you tap the mould on a flat surface. This tends to provide a bit of pressure as the sudden stop from an semi-accelerated start forces the pewter into all the right places. ;)