I can't remember what they were called but I know what you are referring to. I actually have some and you can still buy a type of them at Michaels, in Canada anyways. I found the ones I have on TSC here. My main use for them is on the dinner table during special occasions. You fill a wine glass (or any glass item that will hold liquid) half full of water and color it if desired then you add the oil. A basic cooking oil will do and if I want to add FO I mix it up in a measuring cup first then pour it in my glass. Then you float the disk with its wick in it and light it. The nice thing is you can put one per place setting or use something larger and make a big center piece. If the oil starts to get low you can just add more and if it runs out the water seems to extinguish it. As for the disk melting it has never happened to me but I normally only burn them for maximum of about 3 hours. (the time it take for a full dinner, Christmas or something like that) I assume if you were to burn them for an extended period of time they would get hot enough to melt. I have never had a safety issue with them, but I have a 2 year old and I am very cautious of where I put things.