If you are using powdered MHRB, emulsions are a likely occurrence, even at high PH levels.
The emulsion layer is a combination of the basic MHRB and your solvent (probably Naptha?).
!.Mix your solution less aggressively to avoid the formation of an emulsion.
when it's too late...
1. Add a pinch of salt
2. Add some more NaOH
3. Lightly agitate the solution (More kinetic energy for the emulsion... try using a washer/dryer/subwoofer)
4. Lightly swirl the solution (Again, more kinetic energy)
5. Lightly heat the solution
6. Wait... (+ALL OF THE ABOVE)
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As for your general low yeild issue.
1. Make sure you thoroughly mix your MHRB and basic solution before adding Naptha
2. Make sure you thoroughly mix your solution with Naptha (preferably with added time, not force... because of emulsions)
3. Freeze precipitate... make sure its cold enough (freezes icecream hard...-20C)
4. Evaporate remaining solvent (Any oils left behind probably have spice in them)
Just a note: I prefer to reuse solvent, instead of evaporating it... but evaporation will show you any spice that didn't crashout in the freezer.
Another note: You could distill instead of evaporating... but only if you're comfortable with that procedure.