I just did a bit of Googling on this, mainly because I have a whole bunch in a drawer I was gifted from a crafter who was giving up papercrafts, so I was curious how useful it would actually be.
Not liking what I'm reading so far- lot of crafters saying it's a very poor product, goes hard in the pots, lots of people not liking the finish, and so on. Link
HERE to a UK forum where a question was asked, you can see it doesn't seem to be making people happy! I haven't read to the end, so there may be help for your question, but just from what I've seen, it looks like it would need some sealer sprayed on to make it permanent.