Cannabis, when fresh, is dominated by a cannabinoid called THCA, which is not psychoactive. The process of pressing the hash enables the decarboxylation process, which consists of “removing” the group of carbons from the molecule, transforming them into CO2 in the form of steam or carbon dioxide (smoke). This chemical reaction also transforms THCA into THC – a substance that is psychoactive – through the application of PRESSURE and HEAT. Pressing hash involves a combination of force and mild heat to condense the glands into a solid mass. The shape and size of hash varies depending on the pressing method. When hand pressed, hash is often ball-shaped. Flat-pressed hash may look like thin shale rock, with hardened shelf-like layers that chip along the creases. Mechanically pressed hash is usually a neat cake, like a bar of soap.