**1. n. [Drilling Fluids]**

The volume percent (or fraction) of a mud that is not captured in the receiver when performing the water, oil and solids test as prescribed by API.

Retort solids thus include suspended solids, dissolved solids (salts), charred organic materials and volatile materials that do not condense. For calculations, retort solids are normally assumed to be only suspended and dissolved solids.

Volume percent suspended solids (weighting material plus drill solids) is of particular interest to mud engineers. To calculate that percentage, the volume increase caused by the dissolved salts is determined from filtrate analyses of chloride and calcium ions. For oil muds, the calculations are more complicated.

**See:**
calcium test,
chloride test,
dissolved solids,
drill solids,
high-gravity solids,
material-balance equation,
retort,
suspended solids,
water, oil, and solids test

Retort solids.