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. This means it's NOT pure.
It's sort of like having a bin full of plastic cups and trying to stack them inside each other. If they're all the same, then it goes a lot faster, because any two will fit inside each other. But if there are multiple sizes and shapes, then it takes longer to match them up with each other, and sometimes they'll match up wrong, and the whole process will generally be a lot less orderly.
It's common for people to post pictures online and ask about the patterns, but that's not the part that's going to be the most helpful. You have to watch how it transitions from liquid to solid. Sometimes the lines in the crystals can hint at how the crystals formed, but that can often be misleading. So it doesn't really help to post pictures here, since you'd really need a video to see anything useful.
TL;DR: Watching how it solidifies will tell you a lot more than what it looks like after it's already solid.
Damm dude. Good read
ReplyDeleteGood read. Glad I read that.
ReplyDeleteI remember 15-20 years ago the good dope had a specific sound when shaking a few shards in my hand. Also I noticed what i call heavy smoke, at exhale the cloud would sink to ground level right away.
ReplyDeleteRight the jingle bells sound, how long it took to turn to liquid form and how fast it cracks back in the glass and the pattern of the crackback and the heavy sinking smoke was another helpful sign to follow but why did we use to be able to put it under black light and clearly see what was glowing the best was the best shit? What happened to that old-school test for non chemists?
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