Friday 19 June 2009

Pewter Casting

Making stuff with molten metal is fun. I wanted to start playing with casting metal objects, mostly decorative stuff and the easiest way that I could see to start was with a low melt metal … such as pewter. I wanted to use a lead free pewter so I looked … and looked … and looked some more and found some at the local tip shop. Mostly old mugs and such that people have thrown away. The tip shop usually has some pieces, but be careful, most of the stuff marked “made in China” is lead based pewter. If it is marked as silver pewter, you are fairly safe.

Next I had to find some soapstone (steatite). I was able to source soapstone in small quantities from an art supplier.

steatite

Steatite is a soft stone that is used in making talcum powder, I was able to cut the stone using my bandsaw and then clean it up on my belt sander.

I wanted to carve the stone in as direct a fashion as possible … no power tools, so I picked up some very cheap carving tools from a discount shop.

carving_tools

Most of these tools are rarely used, I mostly use the straight edge and the narrow curved knife shown above.

I draw the basic design onto the soapstone first and then start carving. I find the carving to be very cathartic, and I can get lost in the process. The hardest thing about carving soapstone for making molds is remembering that to reverse the image. The bits that I want raised in the cast, are cut deeper, and the parts that are inset are raised in the carving. Also, using these tools I don’t have a very fine finish (probably because I haven’t practiced much). You can get good results if you work to your level of competence.

YFART_Badge

Here I have made a badge for some friends of mine who are medieval artillery enthusiasts.

I have notched the edges of the soapstone so that I can key the two parts of the mold. On the reverse face, I have carved a gate to allow the molten metal to enter the void.

YFART_Badge_gate

I’ve also carved my initials into the back so that the badge ends up with my moniker.

To melt pewter, I use a simple and cheap portable gas (butane) stove and a stainless steel pot.

Gas_Stove

This gets the pewter from solid to liquid in about 10 minutes (depending on volume).

The two haves of the mold are clamped using a simple spring clamp and sit in a cooking tray.

clamped_mold

When the metal is molten, it is carefully poured into the gate and, moments later, the object can be demolded. Some care should be taken because it is still going to be hot. Always take care when working with molten metal. If your mold gets wet at all … do not use it until it is completely dry. I once cast a metal figurine when there was a tiny amount of water in the mold. It exploded in my face when the water vaporised and I am very lucky to still have two eyes!

Rest the mold between castings as the steatite retains a lot of heat from the casting and can become too hot to use.

Here are some of my castings.

star_buttonYFART_Badge_pewter

The badge needed to be cleaned up and there was too much air trapped. This needed more gating so that the gasses could escape. The carving was not crisp enough either, so I still had more work to do.

The nice thing about pewter casting is that you can melt and pour fairly quickly and remelt and repour. This means that you can refine your design fairly quickly.

When I made the button, I used a wet nylon scouring pad to smooth the inside of the mold. I was quite pleased with the result.

IMG032

The above is an Anglo Nubian goat head that I cast. This is before I cleaned the casting up. The design went through a couple of alterations but essentially looks the same. To clean the design up more, I used a set of fine files (and a Dremmel). I made a pair of these along with a pair of prick eared goat pendants as giveaway’s for the goat club that I am a member of.

All up, the hobby is quite fun and gives you stuff that you can show off. The stove cost $15, the carving tools $2, a block of steatite (6” x 6” x 6”) was about $30 and the pewter has cost me, on average $5 per mug. I melt the mugs down as soon as I get them and make ingots by pouring the metal into a steel muffin tray.

A word of caution. Any molten metal is going to be very hot, it sticks to you and burns. You have to take care and wear safety gear at all times. Don’t play around with molten metal and if you are a kid … ask your parents for their help! Seriously, it really hurt when I had that figurine blow up in my face and I had to peel lead off my eyeball.

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