I did it - today I melted down my first experimental slabs which were still going strong by the way. It worked really well and within 2 hours the new slab was ready, set and could be used. I used a waterbath pot (bought at amazon for 14€). I especially didn't use the microwave because I am not so sure it is safe with all the alcohol fumes which do get released. I'm really excited that it is so easy to reuse the slabs. I have read that one can freeze the pieces if one doesn't need them for a longer period of time. Will try that out too sometime.