@Akira sorry, missed a bit out,
you put the nail polish in the disk, grate matchstick heads into it then put it in the fridge so it sets. I also find it works better if you can get some magnesium in there too.
The exact instuctions were on my old website which is sadly long gone, the backup is on my A500 hard drive which is missing
It does work! several of my high school PCs can vouch for that