It is possible to crumble hash with a grinder, but not without a struggle. First of all, we recommend a metal grinder , because a plastic grinder can easily break with the force you have to use to crumble hash. Hash comes in many different sizes and varies greatly in softness or hardness. Never put too large chunks of hash in the metal grinder, but first make the hash chunks a little smaller so that they fit properly in the crusher.
Then turn the top part of your metal grinder with enough force so that the hash starts to crumble. When the hash is softer you will notice that parts of the hash stick to the blades of the grinder . You can remove this with your fingers or a stick, but you can also soak it loose in boiling water.
Do not light the hash with fire to soften the hash, because that will cause a (large) part of the THC to burn immediately. To soften the hash, you can also warm it between your palms. This takes a little longer, but the quality of the hash remains best intact.