How to make a casting mould?

On this side I would like to show, how I make a casting mould of an artificial body for one of my chicken chicks. How I use it, can be seen on an other page.

I start with cutting a body out of polyurethan foam (PU-foam) (photo 1 & 2). In this case I have cut it after another artificial body. Normally i cut these bodies after the original body, immediatly after I peeled off the skin. Afterwards I wrap the lower half in modelling wax (photo 3).
I cut some grooves which will keep the two halfs together under casting (photo 4). I fill some modelling wax in the damages on the body and put a strip of cardboard around the whole (photo 5).

photo 1, 2 og 3

Following, I mix the silicone and the hardener and fill the mixture in the form (photo 6). The mixture has to be very precise. I mix 100 parts of silicone + 5 parts of hardener. The form is now left for the night.

photo 4, 5 og 6

The next day, I can remove the cardboard and the modelling wax. I repair a little on the body and place a little cone of modelling wax in the one end (photo 7). The purpose of this cone is to create a little hole that I can use for either pouring in casting material or, as in this case, for use as an exit for excessing PU-foam.
The cardboard is put back again and the silicone is smeared with a slipping agent, wich formes a thin layer to prevent the to halves from melting together (photo 8). A new portion of silicone is prepared and filled in the form (photo 9) and the form is, again, set aside for the night.

photo 7, 8 og 9

The following day, the cardboard is removed (photo 10) and the artificial body is taken out (photo 11). After a cleaning, where also irregularities in the new mould are evened out, the form is ready for use.

Now I weigh PU-glue and water (photo 12). The water will make the PU-glue lathering before it hardens.

photo 10, 11 og 12

The form is closed and a clamp is sat on (photo 13). Now it has to stand for a couple of hours (in praxis: another night again). The excessive foam is used as an indicator for the hardening process (photo 14). The form is opened and inside lays an artificial body, ready for use in one of my chicken chicks and the form is ready to cast another body (photo 15 & 16).

photo 13, 14 og 15

photo 16

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