- Trituration: In this method, particle size reduction of coarse granular substances or lumps is carried out using a mortar and pestle or mill. Sometimes even dry powder substances are mixed using this method.
- Pulverization: Soft and gummy substances are difficult to powder in mortar and pestle. Such substances are powdered by adding an inert material that helps in powdering and are removed afterwards. A typical example is camphor, which is powdered by moistening in presence of alcohol and after the preparation, alcohol is allowed to evaporate.
- Levigation: In this method, a solvent is added to the dry powder to form a paste. The solvent is known as the levigating agent. The powder-solvent paste is then triturated using mortar and pestle. In the preparation of semi-solid dermatological preparations, ophthalmic ointments and suspensions, this method is used, which prevent the gritty feeling in these formulations. Typical example of levigating agent is liquid Paraffin.
- Spatulation: In this method, the powders are blended in small amount by movement of a spatula on an ointment tile or on a small sheet of paper. The process is only suitable for small quantities of powder. Powders having potent substances or with a large quantity are not blended by this method, because the process does not ascertain a homogenous blending. Solid substances that form eutectic mixtures are suitable for blending with spatulation because compacting of the powders results from these. Examples of substances that can be blended by this method are—camphor, menthol, phenol, thymol, aspirin, etc.
- Tumbling: Special motorized powder blenders are used in this process, whereby the powder is mixed by tumbling in a rotating chamber. The process is time consuming.
- Sifter mixing: Powders are mixed by passing through sifters, which results in light and fluffy products. The process is not suitable for the incorporation of potent drugs into a powder mix.
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