Why Painters Use Mediums: Purpose, Dose, and What Remains

Painters use medium for many reasons: to change handling, control drying, assist with glazing, reduce solvent use, follow a taught method, or simply continue an established routine. Drawing on practices reported by the Painting Best Practices community, measured studio demonstrations, and published technical evidence, this session examines why a medium is being used, what change the painter expects, how much is actually added, and what evaporates, remains, or continues to react in the paint layer. The goal is not to prescribe a particular medium or rule out their use, but to help painters distinguish a specific material need from preference or habit and make each addition deliberate, informed, and appropriate to the job.