The amount of water present in the capsule shell, expressed on a stated measurement basis.
Also called: shell water content; capsule moisture content; capsule shell water content.
Is shell moisture the same as room relative humidity?
No. Shell moisture describes the shell specimen; relative humidity describes the surrounding air. Shell water content depends on environmental conditions and moisture history, and filled ingredients can exchange moisture with the shell. A room reading cannot be relabelled as a shell measurement.
A moisture percentage must name the specimen: empty shell, fill formulation or whole filled capsule. These measurements cover different material and cannot be substituted for one another.
Three different moisture-related observations
Observation
Object to identify
Room RH
Air conditions, with temperature and observation time
The appropriate range depends on shell grade and measurement basis. Gelatin and HPMC have different moisture behaviour, and grades within one polymer family can also differ.
Record the supplier, grade, lot, sample state and measurement method when reviewing a certificate or complaint. If a report uses loss on drying, retain that method label rather than silently presenting it as a different water-specific measurement. Ask which specification and measurement basis the reported result is being compared with.
Does a moisture result explain every cracked capsule?
Water loss can contribute to gelatin brittleness, including through exchange with hygroscopic contents. Moisture content, mechanical response and storage stability remain separate observations. Retain the moisture evidence, material condition and observed failure location rather than using one percentage as a complete diagnosis.