You'll need anhydrous acetone.. If store bought, you'll need to dry the acetone with baked epsom salt.
First the epsom salt need to be baked, to convert the salt to non-hydrate.
Then you'll pour out some acetone, preferably from a freshly opened bottle (since acetone absorbs water from the air) - to make room for the baked epsom salt. Then add baked epsom salt to the bottle of acetone.
Shake the bottle every now and then. Chill in freezer 12-24 hours - preferably with the bottle standing upright, to make the epsom salt settle on the bottom.
The acetone should be anhydrous now or at least contain less water than it startet with.
You separate the acetone from the soaked epsom salt and repeat the process, but it's hard to filter and you'll risk the acetone absorbing more water from the atmosphere, in the process... If epsom salts have settled over night, the dried acetone can be poured slowly from the bottle, leaving the salt on the bottom.
Crush methamphetamine crystals finely and put it a coffee filter. Place filter in container and pour a conservative volume of ice cold anhydrous acetone over the meth. You can repeat this step 1 or 2 more times, but usually isn't necessary..
Let the filter with washed meth dry completely. Use a fan..
Then salvage your meth.
can't remember duration and temperature for drying epsom salt and proportions, so you'll need to look that up your self..