Rosin refers to an extraction process that utilizes a combination of heat and pressure to nearly instantaneously squeeze resinous sap from your initial starting material. The term “rosin” originated as a method of making a product used to lubricate violin bows. With cannabis, this method is incredibly versatile in that it can either be used with flowers or to clean up hash and kief into a full-melt hash oil. The result is a translucent, sappy, and sometimes shatter-like product. If executed correctly, rosin can rival the flavor, potency, and yield of other solvent-based extraction products.
One reason for rosin’s newfound popularity is that it’s a solventless technique, meaning the process does not require use of any foreign substances. Instead, rosin uses a mechanical process involving heat and pressure to extract the resin from the plant. Other extraction methods utilize light hydrocarbons such as butane and/or propane. Often, these complex and mechanical systems require a lengthy purge to safely remove most, if not all of the residual solvents from the final product.
Rosin, on the other hand, simply uses heat and pressure and does not require any additional cleaning, so your final product is clean and ready in just minutes. When compared to BHO (butane hash oil), the two are aesthetically indistinguishable. Rosin, when made properly, retains just as many valuable terpenes that account for aroma and flavor. However, in a lab test, rosin will never contain a single parts per million (PPM) of residual hydrocarbon. In other words, you are essentially getting shatter without any solvents when using this process.