Marked as used by the Inland Revenue Pollock & Stewart Glasgow- 1943

Sikes’ hydrometers were mandated by British law from the early 19th century onward for determining alcohol strength in distilleries, bonded warehouses, and customs offices.

Inside the fitted wooden case is a complete working system: the main brass hydrometer bulb, a series of graduated brass weights used to adjust readings across different strengths, a boxwood slide rule for calculating proof spirit, and a mercury thermometer signed J. Lizars, used to correct readings for temperature. The paper certificate affixed to the case states that the instrument was officially adjusted and certified on 7th September 1943, confirming its accuracy against National Physical Laboratory standards during the WWII period. Together, these elements place the set firmly in the tradition of British government-regulated scientific instrumentation—objects that were utilitarian, exacting, and essential to the administration of trade and revenue.

When you place a hydrometer in a liquid, it will sink until the weight of the liquid it displaces equals its own weight. The denser the liquid, the less the hydrometer sinks. Conversely, the less dense the liquid, the more the hydrometer will sink. Since alcohol is less dense than water, higher alcohol content results in lower liquid density, causing the hydrometer to sink deeper.

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