Okay. I've had some success with Instant Mould in getting my fimir heads sorted, so I thought I'd put up this wee tutorial to share the things I've learned during the process. This tutorial applies to anyone trying to mould a part like a head, weapon, anything with two sides. Here we go, step-by-step with Doctor Saturday's press moulding workshop.
Find a container not too much bigger than the object you are planning to make a mould of. This is important as you need something that will contain the instant mould so that when you press the part in, the instant mould has nowhere to go, and presses back into the detail of the part.
Pour some boiling water in another container, and add your stick(s) of instant mould. Give it a minute until it becomes soft and pliable. Use the rest of the water to make tea.
Lift the instant mould out of the water with tweezers. If it's quite melty, you're ready to rock.
Press the instant mould into the mould container, to about half way. Make sure you have enough material ready to make the entire mould, as this stuff hardens up pretty quick.
Press your part into the material, in this case, my fimir head. I pressed it face in, not profile, as I didn't want any lines along the face where the second dose of instant mould went in. This turned out to be no problem anyway.
Add the second lot of instant mould, pressing in until you can press nae more. Allow to harden for a few minutes.
This part can be a pain. Instant mould doesn't stick to much, but it can still be a job getting the mould out of the container. I use these rather sharp tweezers to dig into a non-essential part of the mould and pull it out. Pear down the edges of the mould if needs be. Cut it close to the actual edge of the part, but still leave about 3-5mm so it doesn't tear when you take out the master part.
Here's the most vital bit. Press moulding is not going to yield the same results as using liquid metal/plastic, which flows into all the detail, yielding nice, crisp models. The way around this is the application of brute force. The mould isn't going to be two part. First, we need to extract the master part. Cut a line, in this case aiming toward the back of the head and neck, so the mould opens just enough to pull out the part, leaving the moulding of the face and such untouched. Next, carve enough space at the back of the head and neck so you can push in the greenstuff.
The reason for the large opening is to give you enough room so you can shove the greenstuff (or whatever) into the mould's detail using something the size of a paintbrush end to give you a better casting. Keep the end of the tool you're using wet to stop the greenstuff gripping it. I can't emphasise how violent you need to be here. You need to keep adding and shoving in greenstuff until it starts pushing back at you. leave it to cure. Have more tea.
Hopefully, all that agression will have forced the greenstuff into the required shape. If not, try again, THEN melt the mould and it's back to step 1. It took four attempts to get the heads to come out decent.
If so, tea all round. Huzzah!