Early twentieth century humidity reader by Negretti & Zambra
Properly named in their 1950 catalogue as a hair hygrometer or hygroscope, this instrument was used to measure relative humidity in the air with a range of 10-100% humidity.
To quote the Negretti & Zambra catalogue, “The hair hygrometer or hygroscope range 0/100% relative humidity consists of a bundle of hairs or other organic tissue which changes in length when it absorbs moisture.
There are no springs, gears or cords in the mechanism, and errors due to backlash, friction etc, are thus reduced to a minimum.
The hygroscope can be readily checked from time to time, either by wetting the element with a camel hair brush, in which case it should be read approximately 95%: or better still, by means of the wet and dry bulb whirling hygrometer.”
Negretti & Zambra retailed two version of this instrument. This particular version was dubbed the “PH/1 4 inch dial Pocket Hair Hygrometer (Hygroscope) range 0/100% relative humidity; metal case, 4.5 inch diameter overall, finished eggshell black; dial enamelled white with black divisions and figures.” How convenient it was as a pocket instrument could be debated but it remains in complete working order and has great design qualities. Manufactured along the same principals as the hygrometers encountered on antique wheel barometers where a reed of barley was used to create a similar outcome, this updated and more accurate version shows the development of the instrument into the twentieth century.
Negretti & Zambra were a leading name in the production of meteorological and scientific instruments and have a company history dating back to 1850. Throughout their long and esteemed history they exhibited at British industrial fairs throughout and became makers to both Queen Victoria and Edward VII. Owing to changes in the business, the firm ceased the public retailing of scientific instruments sometime around the late 1960 s and continued with a focus on the aviation industry in numerous guises until its eventual liquidation in the year 2000. A sad end to a hundred and fifty years of quality manufacturing.