Trying to make plastic moulds

I have 4 children. The boys, 8 - 10 - 12, are getting a bit too old to enjoy being creative with their mother. They are more concerned with games and playing legos and stuff like that. However, they do love to paint and also to be allowed to run amok in all my crafts thing.
Now the boys wanted to make masks, and of course my little girl, 3 years old, wanted to do the same. And if I have to keep buying masks for them to paint, then I would be broke before the end of the week. They are surprisingly expensive. So I bought two masks and then I use a liquid plastic stuff to try and make a mould. I don't really know if it worked yet as I have to add a lot of layers.
I am a bit pessimistic at the moment, as I think that the plastic liquid has really stuck to the base. Hopefully it will work, but I will keep adding more layers.

Here is what it looks like today.