Having created the mould, the next step is to try some resin casting. The polyurethane liquid casting resin comes in two parts. I put on some protective gloves and goggles, measured 5ml of each and mixed the two together. The foil containers from mince pies make great mixing bowls. (Don’t you wish it could be Christmas every day?). I poured the mixture into the mould and waited for it to set.
After an hour I carefully removed the resin object from the mould. The result wasn’t bad for a first attempt. I broke one of the buffer beams when I removed the mould. Plus, there was a piece missing from one of the sole bars. I don’t remember breaking this, and I couldn’t find the missing piece, perhaps it is the result of an air bubble?
I decided to try again. On my first attempt I’d poured the resin as quickly as I could but the mixture has a working time of 2-3 minutes and this is plenty of time for a small object like this. I worked more slowly and I opened up the mould slightly as I poured the resin, hoping to reduce the chance of air bubbles.
An hour later I removed the cast object from the mould. No air bubbles this time, but I managed to break one of the buffer beams again!
There are mould release agents to make it easier to remove the object from the mould, but I hadn’t brought any of these. I’d heard that some people use baby powder (fine talc powder for babies) and I rummaged through our cupboards but didn’t find any. (We haven’t used this for many years).
In the end I decided to try again and be very, very careful when removing the object from the mould. I spent a lot of time gently bending the mould away from the object, to ensure it wan’t stuck, before I removed it. The moulds are much more robust than I’d expected.
Was I disheartened that it had taken three goes to make one object?
No, because I learnt a lot about how to pour resin into moulds and how to remove the object afterwards. I wouldn’t have learned this if I hadn’t made some mistakes!
Would I try resin casting again?
Definitely. If I want to make several copies of something it will be quicker than making each one from scratch. I think I was quite ambitious to try casting this complex three dimensional object for my first test of resin casting. In future I would cast objects like this as a several flat components (sole bars, buffer beams, strengtheners) and join the resin parts together afterwards. With flatter components it will be easier to pour the resin and remove them from the moulds.
Overall I’m pleased, I’ve made some mistakes, learned a lot and it’s another tool I can use to make models 🙂