SWIP wouldn't presume to teach anything to the real chemists in this forum, and maybe not to some of the more experienced bees either. But he ran into an improvement on the procedure he believes most bees use, and while the changes are very small, they made a huge difference. SWIP bets that you'll be pleasantly surprised at the results if you try it, but only if you carefully follow the procedure.
You will need:
1-2 ehrlenmeyer flasks or ghetto equivalent
2 small beakers, ~50 ml depending on the size of your sample.
Denatured alcohol (the kind with methanol as denaturant works well)
Acetone
Eye dropper
Gently heat a small beaker of denatured alcohol. (Not on a flame, of course, and don't forget to aim a fan to blow the fumes away from any source of ignition.) Put the substance you want to recrystallize in a small ehrlenmeyer flask or ghetto equivalent, and add hot denat drop-by-drop until the sample disolves and cloudiness in the solution just clears.
If the solution has any suspended particles, add additional hot solvent to prevent crystals from forming, then hot-filter the solution through a moderately compacted Charmin plug. Don't use vacuum or crystals may form and get stuck in the filter. Rinse the original beaker 2-3 times with a little hot denat and pour it through the filter. Finally, pour some denat directly on the filter to minimize losses. Examine the solution, and if there is still any trace of suspended particles, repeat filtering but use a more tightly compacted Charmin plug.
Put the clear solution on heat and evap until solids start to appear. Blow air from a hair dryer across the surface if you want to speed things along. Then add hot denat drop-by-drop until all has redisolved and the cloudiness in the solution has just disappeared.
Poor a small amount of acetone into another small beaker. With an eyedropper, add the acetone drop-by-drop to the denat solution until it just turns cloudy. You'll have to look close because it's not really easy to see. Now add just enough hot denat--maybe a drop or two--to make the cloudiness disappear.
Let the sample cool, cover, then place in the coldest spot you can find in the freezer. Be prepared for a surprise when you return in about a half hour.
decant the mother liquor off of the crystals, then rinse the crystals with ice cold acetone. Don't throw away the remaining mother liquor, as it still contains a little of your sample. When you're ready you can evaporate/recrystallize this to recover a little more product.
Like SWIP said, this isn't a departure from the normal procedure, but there are some indicators that help to get repeateable results. SWIP has been dreaming about recrystallizing for several years, and thought he had become somewhat proficient. The first time he dreamt about trying these changes, though, he had to do it over three times before he got it right.
When he finally finished the process and thought the flask was cool enough to put in the freezer, he was disappointed to see no crystals beginning to form. Not even anything on the surface. He stuck it in the freezer anyway, thinking he might get something to fall out anyway. He checked a half hour later to see if it looked promising, and was astonished to see that the flask was crammed with large crystals! They filled the flask up to the line of the solvent, and many were at least 1/4 inch long and 1/8+ inch wide. After less than 1/2 hour! Imagine what it will look like after sitting overnight, or after a second recrystallization. One big diamond maybe?
PP