The moment of truth : the silicone mixture is poored into the container with the original. If you screw up one of the previous stages (original is not properly fixed to the bottom, both components are not well measured or well stirred), you can kiss your original goodbye after this stage. Trust me, it happens. If you're sloppy like me, it frequently happens.
Making silicone molds is easy, but you have to follow the rules or you get punished.
(Your well trained modeler's eye has noticed I am pooring the stuff with my BARE hands, not using a glove. That was only for the picture. I had to remove some of that yoghurt from my hands, and that is NOT recommendable.) When you spoil some wet ready-mixed silicone on your working surface or on any HARD material : leave it be. When the silicone has cured, you can just pick it up and throw it away. Removing liquid silicone is an absolute pain in the neck.
When the container is filled with the silicone, gently tap on the sides with a hard object. These taps stir the air bubbles and make them come to the surface. Air bubbles in the mold become resin bubbles when you start casting. Air bubbles in your resin become small holes (you've seen those in commercial resin kits ,too !) when the resin hardens.

Notice the yellow, red and blue dye tubes in the background...




Let the whole situation cure for a few hours, the mold is hard. I always KEEP the mixture cup with leftover mixed silicone while the mold is curing. I use it as a reference to see how hard the silicone has become. Doing so, I don't have to disturb the mold to find out.
Getting the mold out of the container can be a problem. Lego containers or disposable cups can be useful. When I want to save the container (like this one), I use the same screwdriver/crowbar tool I described in part 2. That is why I stick the original to a piece of styrene and not to the container bottom. The styrene makes it easier to remove the mold, and it does not damage the container when removing.

Et voilà : the result is a mold with four ammo boxes. This is about the easiest shape you can possibly make with a mold. Bent pieces are a lot more complicated to get out of the mold. Start experimenting with easy pieces, and you'll learn from experience how you have to make certain molds to make it easier to yourself. You'll start messing with pooring canals and air canals and... but that's a story I'll tell you later.



I'm not the world's greatest expert on this subject, these are just my 2 cts (€).
If you want to experiment, you can always PM me if you have questions, or post them below.
I really hope you dare to give this a try. Casting resin is scratchbuilding at its best !

Beautiful article jan !! I'm gonna try this for sure.

Thx for sharing those "secrets" with us.

I'll certainly keep your article for future reference, Jan; it is very good. I think I better figure out how to make a master first though

Nic

Jan!!,
Absolutely fantasic 3 part asticles, thanks a million for the excellent step by step!

Jan,

Nice article in three posts. Perhaps you can put them together and ask Jim (when he returns from his holidays) to pub it in the TIPS & TRICKS section.

One question - Do you use anything to help to separate the masters from the mold - I don't know the correct name demoldant ? - or that is only needed when you make the duplicates ?

You need a release agent when you start casting. Several different things can be used. I use a silicon water proofing spray for tennis shoes.

Now........If I can only find the $$$$$$$$$$$$$$$$


Matt

Good way to save those bucks when you need 200 shells and only want to buy 20 . Use it all the time saves the bucks so how much does resin go for in Belgium And Silicon rubber? their General.

Good article general. I have been casting stuff myself for quite some time now too. Easiest way to save a buck or two when you need more than one of anything. The Verlinden value packs that I have were bought for one reason and one reason only...to provide masters for my dioramas. I cast them, put them on my models and I still have what I started out with. I didn't have the luxury of some one knowing how to cast when I firs started, so it was trial and error for me. You articel should be a good starting point for first timers... good job. "Q" :-)

Here's a few extra thoughts...

1) release agents. I tried several products. There's a thread in this forum that specifically deals with release agents.
However, to cast resin I do NOT use a release agents. Resin releases easily from silicone. Only to save the life of the original (depending of the material it is made from) is useful. Release agent can be useful to remove the mold from the container, but not always necessary.

2) copyrights. I do not want to start a discussion on copyrights or other property rights here.
When you use the silicone/resin technique, you can make sharp, perfect copies of an original kit that was marketed by a company. Legally, this is not correct. I will not suggest I never ever did this - at least partially and for my own personal use - but it is wrong.
I would not like anyone to think that I promote the idea of copying someone else's labour.
Copying commercial kits for your own use is generally more expensive than buying an extra kit. This certainly goes for complicated kits that contain many pieces. You need to cast several (which needs great skill in mastering casting techniques) before you break even. And even then you'll get more air bubbles than in the original kit.
Copying commercial kits is only interesting if you need LOTS of them (for a spectacular diorama) or if you sell you copies to friends. If you do the latter, I do not think you deserve a place as a member of this fine community. Be your own judge...

You should be able to get good quality resin and good quality silicone for about 25 € (or $) per liter.
Some brands are more expensive, some less. Ask around with your retailer before you decide on a product.
Get silicone that remains quite soft. Hard silicones break more easily, have a shorter lifespan and are more difficult to demold. Then again, for very large objects hard molds keep their shape, while the fluffy molds may cause deformed objects. To avoid this deforming, you can place the mold in the original tight-fitting container when you cast the resin. Remove from container before you demold the object.