Is it possible that psilocin fumarate is too soluble in etoh, especially with that 4% water? In terms of polarity, its water first, methanol, ethanol, iso, and lastly acetone. That's why tone works best for doing this. Even if you had dry etoh, perhaps it still would not crystallize since etoh is a fairly polar solvent to precipitate crystals out of.
Then when it evaps, maybe the fumarate is hydroscobic to a degree, and it prevents crystallization just like with dmt fumarate and water, it evaps to a goo before crystallizing. Or you have to wait a day or two for it to crystallize.
If you can't get dry acetone, perhaps if you can get 99+% iso it would work.
I bet its the water, and the higher polarity of etoh causing crystallization to be delayed, or prevented from occurring at all (if the fumarate is at all hydroscobic).
But thats just speculation, i do know that fasa with 4-aco/ho in dry acetone works very well. And i was able to base it with lime, which tops out around ph 12.4, seems like the magic spot according to that chart. I noticed little degradation converting gooey brown 4-aco hcl into mixed psilocin/4-aco fumarate salts. Psilocin because i think a good portion degraded into it as it turned into a goo and in the base hydrolysis when i based it with lime paste. It was just as active (qualitatively different though) per mg as white 4-aco fumarate that had not degraded. If you work fast perhaps it prevents the "amine side chain likes to bite back and hydrogen bond with the 4' phenol", that was mentioned by joe dirt.
All speculation though.
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