Taking your rubber, Catalyst, plastic mixing cup, a spatula, a pill cup and your scales (electronic) and not forgetting kitchen towel to clean up with. Place your mixing cup on the scales, set the weight to
grammes and then you should see a weight displayed, this is the weight of the cup and you now need to zero the weight. Pour into your mixing cup on the scales the amount of rubber you think you will need, in this demo we will use 100 grammes. But always word in parts of a hundred ie 25, 50 75 etc. You will get to know from experience roughly what you will need.
Into the pill cup add drops of the Catalyst (small blue bottle) you will need, which in our case is five parts or 6 mil
Do not forget to change the scales or use the measurement on the pill cup as a guide. Then when you are happy pour the catalyst into the rubber and taking a spatula mix until the rubber is a light blue colour throughout, be very thorough with your mixing, with the mixing pot being clear you will see if there are any areas that are missed. You have plenty of time for this, so do not rush, with the product I am using to illustrate it is up to two hours.
Once you are happy with the mix, start to pour it into the mould in one corner of the mould and allow the rubber to find its own level, just a slow gentle pour should do the job. Once you start to get near the top of the mould and the master is fully covered, ease off pouring and allow the rubber to settle, you will see air bubbles start to form and come to the surface; gentle tapping around the edges of the mould should dislodge any bubbles that are sticking. Do not throw away the rubber that is left in the pot, this is your guide to let you know that the rubber is hardened, I usually pour last thing at night, this removes any disturbance of the mould and gives it a clear 8 – 10 hours to set. The following day check the rubber that was left in the pot by trying to pull it away and out of the pot, it should come away clean and if it is thick enough will have a use for when you are folding etch etc.
Taking your mould, start to remove the first layer of bricks and you will notice that there has been a slight bleed through of rubber, this is not a problem and can be cleaned off after you have released the mould and master.
Now place the master back into the rubber mould along with the pour/air sprue guides and the locating pegs and set aside while you remove the clay form the lego bricks/base and clean them up, you will be using them shortly.