More about Mixing and Freezing Henna
By: Krysteen Lomonaco ~ 2/20/2012

From Denise, you'll meet her this 2012 summer season.  Click here to veiw her Bio
My question is about freezing henna.  How do I do it and how long is it good for?
I'm often asked about freezing henna.  It's not hard.  Once you mix your henna, it's only good for about 3 days.  There are some variations on this time depending on the quality of the henna crop or how your powder was stored.  But in general, it's good for about 3 days.  If you're not going to use it all in those 3 days you might want to freeze it so you can use it at another time.
To freeze henna, which put's it in status, just put mixed henna in an airtight container with a piece of plastic wrap push down over the top of the henna.  This helps with moisture that might collect and keeps air away from the henna. 
Be sure to mark the container in some way to show how many days it will  be good for once you take it out of the freezer.  I use a piece of tape and mark it with 3 vertical lines.  If I've used it for 2 days before putting it in the freezer then I mark off 2 of the lines.  When I take it out, I know it's only good for 1 more day.
From what I've been told henna can be kept in the freezer indefinably.  But to be honest with you, I've never had to store it longer then about 6 weeks.  Good luck, let me know how it goes.