High temp silicon pads for vacuum assist casting

I am using vcuum assist casting with solid flasks with a Kaya Cast machine. I have had some metal
melting into the pads and have had to order a new set. Past discussions include using wet cardboard
under the flask and over the silicon pad. I will try that but would like to purchase or have an extra pad
made. They are fairly expensive (>$25) from Otto Frei. I would like an alternate source and perhaps to
make my own. Ideas?

Penny

I buy silicone mold rubber for pewter casting machines 12” round or sometimes you can find sheets of silicone rubber uncut. I then cut to size and put into my vulcanizer cure and then cut the centers out as needed.
Cheaper in the long run then buying pre cut ones.
I also use liquid soap under and on top of the pads makes for a better seal.

Thanks! Where do you get the silicon sheet from? Do you always vulcanize?

Contenti Or Rio Grande also sells it. Yes needs to be cured.

Thanks again, I did try through Rio w/o luck. I have no way to vulcanize it at any rate.
pb