Foam latex, step by step  

Now it's time to make the foam rubber. For this procedure you will need the following stuff:
Kenwood Chef mixer
A clock with seconds
An electrical scale with a 1 gram accuracy
Air moisture meter
Silicone oil (ex Rhodorsil 47 v.350)
GM Foam or Monster makers foam latex
Oven that doesn't have to be used for food afterwards
A 5 ml syringe
and a great deal of patience as it is never so simple as it looks here.

You start with putting up all the moulds you are going to use and brush silicone oil on them and let them dry. The best is to put on the oil the day before. You can use the soap release that comes with the foam kit but I think the silicone does the job much better.
The recipe I used for this batch of GM foam looked like this: 
Latex base: 150 gr. 
Foaming agent: 30 gr. 
Curing agent: 17 gr.
GM colour: 1 gr. 
Gelling agent: 3 ml 

The gelling agent is not added until the last minute of whipping. In the original recipe they say you should use 10 to 15 grams of gelling agent. However, the strange climate here in Sweden means that you have to decrease the gel agent drastically.
A good tip is to use a syringe instead of a measuring cup as it is much more precise.

Now it is time to mix the latex.
The whipping times were like this:
1 minute on speed 1 (basic mixing)
5 minutes on speed. Max. (Foaming) 
5 minutes on speed. 3 (Refining) 
3 minutes on speed. 1 (Ultra refining) 
Now you add the Gelling agent! 
1 minute on speed 2 
The heat of the room was about 22 C and the humidity was 50%.

Now I am in a rush! After the gel agent is in you only have a couple of minutes to fill all your moulds..
With the help of a soaped brush I put in the fluffy foam. You have to think about not brushing on the edges as they can get too thick. When the mouldis filled you carefully put in the positive and press hard.

Now you just have to wait for the foam to "gel". This happens after a few minutes when the pH value in the rubber starts to reach neutral. On the left picture you can see that the foam is still messy and fluffy, but on the right picture 6 minutes have passed and the foam has gelled. Now the finger leaves an indention and the foam feels like some kind of soft rubbery clay that collapses when you touch it. I now place the moulds into the oven very carefully, but I don't put it on yet.
Before I put the oven on I let it stand for an hour and really gel all the way through. If you do this the chance is much greater that it doesn't start to collapse when you turn the heat on. The oven should be 95 C and the foam should be baked for 2-4 hours depending on the foam thickness.

Here I have removed and powdered the finished foam pieces and the result was a success. This  unfortunately is not always the case. Foam rubber can fail in thousands of ways and it happens when you least expect it. Your only defense is to keep careful notes of your work. This can help you later to make a successful batch when everything seems impossible.

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