I had some time today and cleaned off the counter and generally straightened up the shop for the most part. I found a Banksia pod and decided to try and cast it in some Smooth-Cast 326. Smooth-Cast is a urethane resin similar to Alumilite I think. I don't claim to be an expert, but here's how I go about casting.
It says in the directions on the SC that is has an open time of 7 min. once mixed. That's plenty of time, but you can't waist time looking for something so you have to have all your stuff ready.
Here's what I generally use when I cast. The SC has a part A and B and is mixed at 1:1 by volume.Here it is getting ready to be mixed I added some blue dye, turquoise and pearlescent powders to the mix.
I place the banksia in a form. I cut the pod so that it would fit tight and wouldn't float. I was able to get two pieces that fit nicely. I marked on the form where the middle of each piece is and where the seam between them is located so when I cut them apart I can get the best blanks. I didn't get a shot of the poured form, because I mixed too much resin and didn't want to waste it so I used the excess on a single blank form that I have. I put a cutoff of the banksia in this single form and used it for the excess resin.
I placed both forms on a tray and put it into a paint pressure pot that I use as a pressure chamber. I ran the pressure up to around 60 psi. Why 60 psi you might ask? The pot has a pressure relief valve that is supposed to be set at 80 psi. Well it's not or my gauge is off! I popped it at around 70 psi once and it scared the holy crap out of me! So, I stop at 60 to 65.
I'll let the resin sit in the pot under pressure overnight. I've taken them out in an hour before, but I'm not in a hurry so I'll let it sit.
That's probably as clear as mud!