Then they seal it in airtight containers and store it by burying it or keeping it in cold rooms at near freezing temperatures for months, if not years, to allow it to mature. If done right, this maturation process reduces the amount of the volatile terpenes and improves the taste when smoked. These terpenes cause coughing and irritation to the lungs and are very evident with hash made with freshly sieved tricomes. Hash made with undried skuff oxidises very quickly, loosing thc rapidly and often has mould growing through it after only a few months of storage. I consider hash like this to be ruined beyond redemption.
Some people store both buds and hash in a freezer as a long term method of storage.
We did some subjective trials trying both methods and we found that that even a few days in a deep freezer causes a change in the type of high. It seems to take the top edge off and make the stone more couch lock. Other than that, we kept samples for 3 years with no apparent loss of potency. I have to say the samples kept in the salad crisper were everyone's first smoking choice rather than the freezer samples. I don't know why, but once skuff has been pressed into hash, it produces a much more complex high than the unpressed sample.