Phin ( ) hinted at this in his first post, but my nicest crystals came from seeding liquid DMT freebase.
You can crash out liquid DMT by supercooling a saturated solution in a saline ice bath in the freezer. The freebase is cloudy white and will crystallize spontaneously if you even look at it wrong. Use extremely clean glassware and a steady hand. Watching shards form before your eyes because you jostled the flask is really cool, but it means you have to start over.
To get the solution and seed crystals, you need to clean up your regular pulls until there is little to no yellow/orange goo. I usually recrystallize with heptane, but you can also use chilled absolute isopropanol to selectively dissolve the goo and leave the crystals behind.
Once you have clean shards, dissolve them in a minimum of barely warm naptha, and run slowly down through the temps as Phin outlined. I had better luck with naptha than heptane, it's just too hard to supercool a heptane solution, crystals precip and then grow much too fast.
The solution of supercooled DMT and naptha will form layers, and you can carefully pipette off the crystal clear solvent from above the cloudy freebase.
Once you've got supercoold DMT freebase in a flask with most of the solvent off, you need to slowly bring it up to room temperature then seed it and cross your fingers. Most of the time it spontaneously crystallized, but a few times I grew individual crystals ~300mg over the course of a day or two.
My guess is the really huge crystalline chunks you see on Erowid are the product of distillation, which needs to be carried out under an inert atmo with very careful temp control because the DMT will tend to clump and scorch in the distillation flask as you near dryness, probably using an oil substrate in the distillation flask is the answer but I never tried it. Inert atmo with vacuum and an extremely short column with hot water above DMT MP running through will mostly stop spontaneous crystallization in the joints. DMT distillation sucks.
Anyway in my experience you really need liquid DMT to grow big chunky crystals, and the more of it you have laying around the better.
Edited by Defiance, 02 January 2018 - 06:56 AM.