First of all, credits to Jeff Brooks for he was the one that taught me. It's time to share the knowledge. Keep in mind, this walkthrough is meant for a one-sided casting which is more suitable for cating resin bases or terrain. I have yet to successfully make a two-part mould, for I am just a servitor, and need to learn more from the Forgemaster.
Before you start, make sure you have all of these available:
- a plastic container/CD rack
- RTV silicone and catalyst
- silicone release agent
- putty/modelling clay
- the 'master'
- double-sided tape/PVA glue
The very first thing that you must do is to plan; how big your 'master' is going to be and make one. Quoting Khairul: "If you fail to plan, you're planning to fail." Some very important useful tip from Jeff: (1) make sure your 'master' is solid and secure, and (2) avoid undercuts whenever possible. The size of the plastic container that you're going to need is determined by the size of your 'master'. Pictured below is a plastic container I used, overturned, and a hole made at its base. Please ignore the blue stuff for now.
Let's move on. These are my 'masters', glued to the lid using a double-sided tape. Remember to make sure that the base is totally clean, and the 'master' is glued properly and evenly on all sides.
This is the RTV silicone I used. My advice: read the manual and follow exactly as written. Make sure you mixed enough catalyst needed to the amount of silicone used, and pay attention to the mixing ratio; is it per weight or per oz. Unless you have a micro weighing scale, I do not suggest the ones mixed per weight (although they tend to be cheaper than its counterpart).
Once the mixture is ready, it is ready to be poured into the container. There are two things that you need to pay attention before pouring it:
(1) the lids are tightly shut, and packed with putty/modelling clay. Yes, that's the blue stuff in the picture.
(2) apply silicone release agent generously over the master and base of container. I used the spray can agent, while a friend of mine swears by vaseline gel. Well, either way works as long as you get the intended result.
Once those two things are secured, pour the whole thing in and leave it overnight. It should be perfectly cured after 24 hours under room temperature, but it could be much faster if you happened to have a vacuum-pressure pot. However, if you have mixed the aforementioned catalyst insufficiently, please be prepared to wait up until 2++ weeks for the mould to properly cure, regardless whether you have a vacuum pressure pot or not.
This is how the mould should look like after it cured and released from the container. Extract the 'masters' gently and this is where the toothpick came into the picture. Once all 'masters' are extracted, the mould is now ready for resin casting. There are lots of two-part liquid resin out there, each with its pros and cons (and price). You'll need to do some research here.
And there you have it, a quick walkthrough on how to make a mould for resin casting. A dear friend of mine who migrated to Australia gave me his set of vacuum suction cups to use for moulding (pictured below). I have yet to test them as the stuff that I currently need to mould were quite large. Rest assured, I will utilize them someday.
Hope this helps, and feel free to ask any question. Hope you'd enjoy making a mould as much as I did.