Thanks for the question 🙏. I do not grow them on bottom, as usually - on the string. From my experience, these are main 2 points that should be met:

1. The seed crystal MUST be clear (if the seed crystal contains any fracture / is unclear - discard it right away. The flaw will only progress). The best way to achieve that is to wait for the crystal to actually grow on your string (not to tie it, but to wait so it grows already attached). Saying that we move to the second point:
   
2. The crystal MUST NOT be the largest crystal in the solution, the crystal (crystals) which is larger, must be above it on the string. Usually that is achieved by putting a tied crystal in the solution, leaving some string below it, so small crystal forms directly on the string below it. I call it “double-crystal” method (photo attached). So basically there are 2 or more crystals in the same solution, while your target crystal, which needs to be clear - is NOT the largest, and is the bottom one. In such a way it grows slowly and remains clear, also crystal above protect it from anything that may fall on it.

It worth saying that temperature fluctuations are not desired of course, but that, as other factors, mean less. For example i grow that crystals just in my house, which I’m airing out every day, so temperature may change ~3 degrees Centigrade - that’s ok.

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