Concentrates made with water, ice, heat and pressure rather than with a solvent: ice water extraction and bubble hash, dry sift, and rosin pressed from flower, sift or hash. Mechanical separation, which is why the input quality sets the ceiling.
Nothing in this sub-board adds anything to the plant material, so the result cannot be better than what went in. A wash separates intact resin heads from plant matter by agitation and sieving; a press melts and squeezes what that wash produced. Both reward fresh, cold, well-grown material and punish anything mouldy, over-dried or roughly handled.
Two things decide the outcome more than technique does. Genetics and freshness set the yield and the grade before the first bag goes in the bucket, which is why fresh frozen material is now the default input for a quality wash. And temperature discipline runs through everything: warm water in the wash and too much heat in the press both trade the aroma compounds for weight.
Where to start