Hi, I performed similar experiments myself on recrystallising TCNQ and a number of polycyclic aromatic hydrocarbons. I tried using a variety of solvents including acetonitrile, THF, toluene, cyclohexane, and DCM. I found that acetonitrile worked quite well, and I would expect, due to the structure of THCA that the interactions between the solvent would be favourable. You could try the above solvents individually and then maybe try mixtures of different ratios to see which works best for you. You might need to try something a bit more polar, but I suspect this might be too favourable and you might struggle to get it to crystallise at room temperature. To save wasting THCA when testing solvents you may be able to recover it by cooling in an ice bath or a dry ice bath. Note, always check your MSDS sheets for solvents before use as some of them (like THF) can be dangerous if handled incorrectly. Thanks, Alex