THE DEFINITIVE GUIDE TO "CRACKBACK", AND HOW TO USE IT TO GAUGE PURITY
Okay, so "crackback" is basically a ghetto version of testing the melting point range. A scientist might describe it as " qualitative observation of crystallization as a means of approximating melting point range ." Basically, a pure substance will solidify in a noticeably different way than a mixture will. Now, when watching a molten pool of whatever the fuck you happen to have, you will typically see one of two things: In some cases, small number of crystals will form at the edges, and then the whole pool will slowly solidify in a wave outward from the initial crystals. This means that the substance is most likely pure. It doesn't necessarily tell you what it is, only that it's reasonably pure. So it's good to check using at least one other method to identify what it is. In other cases, it'll sort of solidify around the edges at first, then gradually get slushy-looking, usually with a molten spot in the middle as the last part to finally solidify