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[Ash]

Did you use fresh leaves?

If so, then some weight loss is to be expected.

 

[smokerx]

If dried leafs used you had to measure something wrong at the beginning or your scale is not good. There is no way you could lose so much.

Are you sure no spice was left in the glass ?

 

[Precog]

As above, I would be sure to check the sides/bottom of whatever your evaporating container was for excess spice. Otherwise I can't think of anything else but the possibility of a measurement error.