Wednesday, 3 February 2010

Pewter Casting

This post is going to take you through the bits and pieces I have been doing in play.

The first thing I started with was making moulds from cuttle fish. At first this was done by pressing objects into the cuttle fish and then I moved on to making shapes on the laser cutter. The cuttle fish works well for making moulds because it is relatively soft so making impressions is easy and it gives the mould a very good surface finish.

These shapes have been cut using the laser cutter. I have made a range of sizes to see which would make the best impression in the cuttle fish and to have a physical model to see the best size for the charms. From this I have decided that I want/need larger charms so that the detail is more obvious they stand out when hanging from a door but also because they make a better impression in the cuttle fish.


This image shows the two halves of a cuttle fish mould. The mould is prepared by sanding the soft side until it is flat and sits flush with it's pair. You may need to trim the edges on the band-saw so that they are the same size.

You can now make the impression. Press your shape in with your fingers, starting with the edge and work into the middle on of the model until you get it to the depth you require. Depending on the size of you cuttle fish and your model you might be able to make two impressions on the same piece. However to make sure the molten metal does not get stuck near the top of one cavity and not make it into the second you should add extra channels as shown in the picture. These can be removed easily later. Last thing to be done is to make a funnel shaped opening at the top of the mould for filtering the molten pewter in the the cavities and clamp the two pieces together.

The cuttle fish is very brittle. The image above shows the remains of cuttle fish that broke whilst pressing a model in.

Once the mould is ready and clamped together you can start to melt the pewter. It has a relatively low melting point so it can be done in a metal pot on a camping hob. It will take about 10mins to melt the pewter, and once it has you can pour it directly into the mould. It will need about 5mins to cool but it will set within a minute.

This image shows the a close up of the impression Unfortunately when removing the cast some of the mould broke off. If it had been removed cleanly the mould could have been used again by simply pressing the model in to redefine the shape of the cavity. This cuttle fish can however be used again but it will need sanded back and the impression made again.

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