A home roast tastes grassy, or flat and bready
Coffee you roasted yourself tastes sharp and vegetal, or dull and papery, despite being freshly roasted and rested.
Safety note
Roasting involves high temperatures and flammable chaff. Never leave a roast unattended, roast only in a well-ventilated space with equipment designed for it, and empty the chaff collector after every batch.
Likely causes and adjustments
Try one adjustment at a time so you know what actually changed the result. Start with the first cause below — if it doesn't help, reveal the next.
Cause 1 of 5 · Commonly the cause
Underdevelopment — the roast was dropped too soon after first crack
Did you drop within a minute or so of first crack starting?
Extend the time after first crack on the next batch, keeping everything else the same. Grassy, sharp and thin is the signature.
Related issues
Learn the technique
Step-by-step guides to the skills this problem comes from.