Concentrated cannabis extract is obtained from raw cannabis plant material using a mixed solvent extraction process. The cannabis is soaked and agitated in a chilled mixture of butane, propane and isobutane. After removing the solid plant material, the remaining solvent mixture, now with dissolved extracts, is heated to remove the solvents. The remaining, viscous oil is then heated in a vacuum oven to purge the traces of solvent and result in a brittle shatter.
