Casting Bronze
22 Dec 2019Over the last few years I have moved away from buying gifts and into making things. This is us fighting the man on consumerism, but also a cool way to make gifts really personal.
Let’s start with the finished product…
I started after seeing one of Alex Steele’s casting videos. And decided I would start in much the same way, by carving wax.
I should also mention that I was very lucky to have the help of a professional to guide me through the journey. This is the reason everything turned out so well on my first go. It also explains the next step. So rather than try to cast straight away, we made silicone molds of my wax originals.
This way we could make many more if anything went wrong in the casting process. And it all turned out so well that now I want to try to sell them, so that’s a bonus.
Here you can see we attached all the wax carvings and casts to a wax cup that we will use to cast from. This first time I used a combination of both the green carving wax and some special brown wax, this way we can see the preformance of them.
Now we coat the wax in a ceramic shell, the first two layers uses a finer slurry and sand to keep the detail, then thicker ones are used to build up the strength.
When we did the burn out (heating it up to not just melt, but evaporate any remaining wax), we noticed that the green carving wax expanded more than the softer brown wax. This sadly broke the shell around these pieces and we needed to seal over the cracks. We ended up losing a piece this way and two others had noticeable seamlines where we sealed them back up.
What you see above is proof of the professional help I was getting. We used the same ceramic shell mortar mix to join the ceramic crucible to the ceramic shell and with enough bronze inside (10 times the weight of the wax). Notice that there is also a little peep hole that we use to check if the bronze is molten.
When it is ready we take it out of the furnace and flip the contraption into some sand. The bronze flows into the molds and the crucible on top helps to insulate the remaining top loaded bronze. This insulation helps to prevent shrinkage because the bronze cools in the molds first can can pull from the above molten bronze through the sprue.
Taking off the ceramic shell, these came out really well. Much better than my first wax casts in silicone interestingly enough. As you can see the detail comes out really well. Next time I will have to work more on my wax carving. So much easy to get it right first time in wax, makes for much less time sanding and filing bronze.
After some clean up and some polishing they look really good. Very excited to make some more.
