The term Bubble hash is given to hash made from pure trichomes. When lighting up traditional hashish, impurities in the resin will burn. Pure, unadulterated cannabis-trichome resin.
Plant material (either dry or fresh-frozen generally) is mixed with cold water and ice, then agitated manually or mechanically in order to break off the now-brittle trichome heads. This solution is then filtered through specifically-sized screens to remove anything undesirable, leaving behind a relatively pure finished product.