As some of you know I'm building a roof for my tower project and need some ridge tiles to cover the corner joints between my roof casts. The first idea that popped into my head was of course scratchbuilding them and so I started thinking how the hell am I suppose to make small 0,4-0,5mm plaster cones that could be made into ridge tiles. After around 15 minutes I've decided to use plasticine (nonhardening modeling clay) to make small moulds based on the tip of my pen, which is luckily cone shaped. So I cast 18 small tip cut cones, added texture to them and made a small dryfitted piece, which looked like this:
I've posted this in my previous topic and since no one had anything to say I've thought that it must look ok and so decided to make a silicone mould of the 18 cone shaped pieces. I had my camera nearby and also decided to take in-progess shots and post them here to help anyone who just starts at making molds. So here we go:)
1. Make sure that the object you are trying to copy is clean and protected from sticking to the silione stuff. So anything which is porous should be varnished or protected with something else, or the gooish silicone stuff will stick to it and make it harder to get out of the mold. I used 18 cone shaped dental plaster pieces and covered them with a product that seals the plaster and protects it from soaking water and stuff like that. Attach the object to a flat and nonporous base, like here:
2. The next step is to build a small box to surround the object. The box will hold the silicone until it cures. I built mine using the wonderful LEGO's. I also used plasticine to attach the box to the base and make sure that the box doesn't leak:
3. Now you need to calculate how much silicone you need. You do this by measuring the inside of the LEGO box and calulating it's capacity. You also need to calculate the volume of the object. Now you substract the object volume from the box capacity and you have your desired silicone ammount:). Take a medium sized container and pour the silicone into it. Now weigh the whole thing using an electronical scales like here:
or a normal kitchen scales.
(remember to first weigh the empty container and then substract this from the total weight of the container and the silicone)
4. The next step is to measure the ammount of hardner you need. Basically the hardner is the stuff which makes the whole mix hard:) if you add too much the mix will start to cure too fast making it impossible to pour it from the container to the box. If you add to little you will be left with you object covered in goo and completly destroyed. This step is really important so please make sure you read the label of your silicone product well and that you measure everything precisely. My product label says you need to add 3 parts of hardner to 100parts of silicone, so basically it's 3% of the silicone weight. I used a syringe to measure it and here you can see both parts ready to be mixed:
5. Now all you need to do is mix it WELL. And I mean really put your heart into it:) if you think it's mixed already, mix it some more. Than it's ready to be poured, but before that happens, wait around 15 minutes for the bubbles to come out onto the surface of the mix. You can help them by tapping the bottom of the container with your hand. If you think it's ready, pour it:)
6. Wait for the mixture to get into all the places of the box, if it's not cooperating use a small spatula or a toothpic and make it move:) also tap the whole base to get rid of bubbles from the mixture.
7. Wait a day or so, it depends how fast your silicone stuff cures.
[more pictures coming tommorow, I need to wait for the mold to cure:)]
If everything went well you'll be left with an undamaged object and a fully usable mold:) Happy mold making!! and hope it helps:)
Take care,
dsc.
