I use an organza bag, and put a lotion, soap, and poof, and they always sell like hotcakes, around the holidays. They are nice because you can mix and match, whatever you want to put in them.
I went out and bought one from Joanns today. They say Best Value Comfy Candle Warmer. Price $4.99 UL Approved, 17 watt. They come in a yellow package. I have had mine going now for 2 hours, and it is not getting hot on the bottom, a little warm, but I can touch it, so not that hot.
I had this happen also with a few different FO's in my 6 oz tins. I now, paint a coat of Mod Podge, in all my tins, before I pour into them, and it has solved the problem.
I bought some of these also, and painted them gold, and am going to put a 3x6" Christmasy colored pillar candle on them, and see how sell at my next Craft Fair.
I use OK 6228, and a RRD 37 wick for mine, but I do not burn them over 3 hours, and that information is on my warning label also. I have never had a problem, with them!