On the entrance floor of Building A of IPQ, in front of the elevators, near the Metrology Museum, we can see one of the most important pieces under IPQ’s custody: the calibration balance of the Brotherhood of St. Eloy).

This piece, of great beauty, is inside a wooden cabinet, from the 18th century. It has a wooden column with a quadrangular section, bearing a plaque showing a few inscriptions. The 2 pans were initially suspended by strings made of green twisted silk.

The balance sits inside a wooden cabinet with diamond-patterned glass doors. The cabinet measures (1.60 x 0.66 x 2.90) m and has 3 iron locks. The section below has doors where the weights are kept.

The suspension of the pans is now made of metal. The scale is set to oscillate by the usual system of the day – a cord with tassels that serve as brakes. 

This balance was described in the inventory of January 5, 1788:

“One arm of the large balance bearing a label inscribed with silver letters, brass pans and green silk strings, and with two rests made of brazilwood with its golden-brass rings that are for putting under the pans.”

The range of the balance must have been 1 quintal, i.e., 4 arrobas, and its sensitivity goes from 0.49 g for a load of 1 ounce to 1.66 g for a load of 1 arroba.