Vents, vents, vents
It’s casting day. So I melted down two bars (250g each) of the tin alloy Sn95Sb4Cu1 (that is 95% tin, 4% antimony, 1% copper) and set the temperature dial to 350 degrees C (that’s the maximum rating of Econosil). Then I pre-heated the mould halves in the oven to 100 degrees C.
For casting I used a different talcum powder I bought along with my metal specifically designed for casting (according to the label it also contains club moss spores). Just to be on the safe side, I wore a dusk mask as talcum can be contaminated with asbestos if it’s not cosmetics-grade. After every second pour, I powdered on new talcum. Quite obviously you should also wear eye protection and some gloves when you handle molten metal.
On top of the molten metal (inside the solder bath) you will see slag collecting – you need to scrape that off with the laddle until the surface is shiny and clean before you start pouring. I used two plastic clamps and a thin MDF sheet on each side to hold the mould halves together. After a few test pours, I realised that air could not escape, so I started adding more and more vents until the metal was able to fill out the mould completely. Apparently, the temperature of the mould plays a role how successful your casts will be: if it is too cold, the metal will get shocked by the temperature difference. So it took a few casts for the mould to become warmer and to achieve better results.
Result of an average cast
Overall, I am very happy with the outcome for a first attempt. The muscular details get reproduced quite nicely across all three arms. After a few attempts, I was able to get the hands on the two individual arms with all fingers cleanly cast – on one hand even with a subtle indication of nails. The axe came out rather nicely – I like it more than the deformed and broken master. Most of the casts feature almost no mould lines and if they do they compare to what you get from commercially available miniatures. However, I find small details (such as the nails and the sharp transitions on the axe head) somewhat washed out – perhaps the reason I don’t get many mould lines: those are details after all. I don’t know if this is due to small air pockets, the temperature differential between mould and pour or something completely different. If it is the former, this may be hard to overcome with gravity casting. The latter could be solved if the mould reaches working temperature. Some people recommend tapping the mould right after pouring but I’ve also read that you should not do that. I’m going to test that more systematically in a future casting session.
It should be said though that these arms are perhaps not the best objects for studying the degree of detail, so I’m going to go ahead with the chaos dwarf hat as initially planned (if it does not work out, I can still send in the master to a commercial caster). Also: I am pleasantly surprised how fast you can cast. If you figure out where to place the vents (like on the arm in the middle), you can churn out quite a few good ones in a short time.
All casts of the day.
Detail on the first arm: most successful casts. After a few attempts, all fingers were cleanly cast, even some indication of nails.
All weapon arm casts: either the arm or the weapon were cast completely. In the beginning I did tap the mould which seems to have resulted in more successful axes but without the arm. Without tapping, the opposite result. But I also added more vents, so this likely contributed to the outcome.
The only complete weapon arm. You see the washed out detail on the fingers
Detail on the third arm: I forgot to add another vent at the triceps here causing miscasts due to an entrapped air bubble