When selecting a candle tart mold be sure that what you choose is rated for use with hot wax. The wax you pour into your molds will be upwards of 175-180 degrees Fahrenheit so a flimsy receptacle just won't do. Molds should be made from metal or a heat resistant rubber. Molds made especially as a candle tart mold from a reputable supplier will be heat resistant enough to be used with hot wax. If you want to save some money, you can use a mini muffin tin as a candle tart mold but it can sometimes be difficult to get the tarts out of the molds once they've cooled. If this is the case, put the tarts in the freezer for 10 minutes and then give the molds a tap. The tarts should pop right out. If you really have difficulty with a certain candle tart mold releasing your tarts try using a spray on release agent before pouring your tarts next time.