What tek are you using my friend?
Might I recommend performing extractions with less plant material until you really have your process down?
The yellow sticky product sounds like it's goo. Goo is good. It's mainly plant fats and other alkaloids if I'm not mistaken.
A less than 1% yield can arise for a number of reasons: method of extraction, quality of bark, water used, etc.
The evap test is the best way I know to test is your solvent if safe. If there's no residue then it evaporates clean.
If you're still smelling solvent, then you haven't evaporated it all off. Tilt the dish in front of a fan and allow them to dry.
I don't know about "purer" but it will work. If concerned about impurities, re-x after you collect your yield.
Hope this helps.
One love
What if the "truth" is: the "truth" is indescernible/unknowable/nonexistent? Then the closest we get is through being true to and with ourselves.
Know thyself, nothing in excess, certainty brings insanity- Delphic Maxims
DMT always has something new to show you
Question everything... including questioning everything... There's so much I could be wrong about and have no idea...
All posts and supposed experiences are from an imaginary interdimensional being. This being has the proclivity and compulsion for delving in depths it shouldn't. Posts should be taken with a grain of salt. 👽