This article describes the basics of small form metal casting. It is only one of many possible methods. Its main advantage is a little trick, which helps to avoid mould lines.

Disclaimer: I do not intend, nor do I recommend, that the techniques used in the article be used to infringe anyone’s copyright or other intellectual property. The techniques shown should be used for your own creative work.

Materials used:

1) Silicone. You will need a pure silicone, preferably transparent.
2) Plaster. Any plaster which doesn’t harden at least for 4-5 minutes will do.
3) Metal with low melting-point. There are a number of different alloys. Some recommend a 50/50 mix of solder (40% tin) and Rose alloy. I prefer a special alloy used by dentists. It has several advantages: it is harder then alloy GW uses, has a very low melting point (90ºC) and is free of lead. Its disadvantage can be its price.

Let’s assume you need a number of shields with Sigmarite symbols and don’t want to sculpt each one separately. The first stage is making a silicone form. Take the source model (figure 1-1) and attach an intake and a vent to it (figure 1-2). Glue the resulting construction to the piece of cardboard – it makes applying the silicone more handy.

Now, apply the first layer of silicone on the model (figure 1-3). It is the most important operation, as the quality of the first layer to the greater extent determines the quality of copies. Remember that the silicone doesn’t flow and fill all cracks and holes by itself. You need to carefully apply by small portions over each detail of the model. A simple toothpick does the trick.

After that, apply 2-3 additional layers. They don’t require that much accuracy and are mostly necessary to make the form durable. 2 additional layers are enough for such simple model as our shield (figure 1-4,5). The next layer may be applied only after the previous layer fully hardens. It usually takes about 8 hours. If you don’t want to wait, you can try and heat it to 60-80ºC. At this temperature it hardens after one hour. However beware of the smell!

Now you’ve got a silicone cocoon. Cut off excess cardboard. (figure 1-6) The first stage is complete.

Figure 1

The second stage is making a plaster form. Its task is to properly hold the silicone cocoon during the casting, preventing possible deformation. First make a casing (figure 2-1). It can be made of various materials, such as cardboard, or Lego parts or whatever you have at hand.

After that, fill the casing with the plaster (figure 2-2) and press the silicone form into it. The intake and the vent must touch one side of the casing. The thickness of the plaster layer must be greater then half of a thickness of your silicone form.

When the plaster solidifies (you can easily tell it when it warms up) cover its surface and the upper part of the silicone with Vaseline or liquid soap. This is necessary if you want to separate the next layer of the plaster. Then fill the casing with this next layer (figure 2-3). Its thickness should be equal to the first layer.

When the plaster solidifies, remove the casing and separate the plaster form parts (figure 2-4). The second stage is complete.

Figure 2

Now it is time to remove the source model from the silicone form. Take the sharpest scalpel you have and carefully start cutting from the side, where the intake and the vent touch the surface of the cocoon. Here the little trick mentioned in the beginning of the article comes into effect. DO NOT cut the silicone form in two. Cut it just enough to pull the source model out. Let it open like a book (figure 3-1). It keeps the parts of the form perfectly arranged against each other and helps to avoid mould lines.

After that treat the inner surfaces of the form with graphite (figure 3-2) and you are almost ready to cast your model.

Figure 3

Now you will be working with molten metal. You know, it is hot! So make sure you have some protection – gloves, apron or similar outfit. Also the working area should be well ventilated due to fuel and metal fumes.

Make sure that intake and vent holes are clear. Put your silicone form again between the plaster slabs and somehow fix it together. The most primitive method is shown on the picture (figure 4-1). Melt your metal (figure 4-2) and pour it in the form through the intake. Wait until the metal cools down, disassemble the form and take the copy out (figure 4-3). It is easer and faster then it sounds. The first copy may be flawed, as the silicone form needs to be warmed up. The first casting does exactly that. Note that flawed copies and also waste metal from funnel and vent can be heated again and reused.

After that the only thing is left to do is to cut of the sprue metal and do a little filing (figure 4-4). The copy is complete!

Figure 4

This method allows sufficiently precise copying of almost any form, providing you can cut it out of the form. It is most effective when you need a number of similar objects – shields, armor plates, cloaks etc. The form gradually erodes with each casting, but if it is done properly, you can make some 20 copies with decent accuracy. The quality depends both on quality of materials and your skill. As with any craft, you will improve with time.

Special thanks to perambulator for forging the shield of words… eh.. wording the disclaimer. :::cheers:::