^^^
Ive done extensive research with (3,4-Methylenedioxypyrovalerone, MDPV) and one thing Ive learned is never expose this chemical to open air for more than a few seconds. It is highly unstable. Prolonged exposure to the open air will begin a rapid physical/chemical decomposition that is irreversible and will continue even if re-packaged.
Recommended Storage Procedure:
-I would highly suggest that you use TWO containers, the one your MDPV was originally packaged in (usually sealed with air pressed out, if you order through a reputable distributor), and a second of your choosing (make sure its something your able to press the air out of, do not use a vile).
-Take what you plan on using initially* from the original container and QUICKLY transfer to your secondary container. Press the air out of your containers and store the original in a cool dry place.
*This amount should be regulated according to your personal rate of consumption to last approximately 6hr.
(Assuming that your chemical hasn't already decomposed before arriving from the manufacturer, 6hr is short enough that if handled properly, your secondary contents wont begin decomposition while also allowing your main supply to remain sealed most of the time.)
IMPORTANT:
NEVER STORE ON AN OPEN SURFACE SUCH AS GLASS A TABLE
BTW ajay353, if vaporization/inhalation is your preferred method of consumption i would also recommend that you only place the amount you would normally take in one hit. unlike methamphetamine, those "sweaty" spots you are referring to are also highly unstable when left exposed to open air, so do not try to reuse already melted chemical. Also, ditch the blow torch. MDPV's melting point is only 209.3 °C (409 °F), anything beyond that, MDPV looses its potency.
If you have other question, feel free to ask.
Hope this info has been of help.