Sinkfloat

Sinkfloat, also called sink–float analysis, is a simple laboratory method used in mineral processing and materials science to gauge the relative density of a solid sample. By placing particles in liquids of known densities, the particles will either sink or float depending on whether their density is greater or lesser than the liquid. This information helps estimate the material’s specific gravity and informs decisions about suitable separation methods, such as dense-medium or heavy-liquid separation.

Procedure commonly involves preparing small, dry pieces or crushed particles and testing them in a series of liquids with different densities. A single-density test uses one liquid to split material into a sink fraction and a float fraction. A multi-density test (or float-sink test) uses several liquid densities to build a distribution of densities within the sample. The results yield a density profile that can be correlated with metallurgical properties or quality criteria.

Applications and interpretation focus on separation planning. The test helps determine an effective cut-density for separating valuable material from gangue, guiding equipment choices and process conditions in ore dressing, coal preparation, and materials testing. It is especially useful for rapid, low-cost preliminary assessment before more detailed density-based separations.

Limitations include variability in particle size, shape, and porosity, which can affect sinking or floating behavior. Porous materials may become saturated with liquid, while reactive or soluble substances can alter liquid properties. The method also relies on the availability and safe handling of dense liquids, which can be toxic or corrosive. Despite limitations, sinkfloat remains a widely used, quick-screening tool in physical methods of material characterization.