On one hand we are often confused by the outweights of rare animal opium weights, and on the other hand we already know that the metal used for casting are measured exactly so as to reduce the difference between a new opium weight and the standard to a minimum. Even the amount of bees’ wax, necessary to form the mould, was exactly weighed.
Wax was that of wild bees and was transported to Mandalay by boat, sometimes from distant parts of the country. Many families earned a part of their living by selling bees wax. The weights used to be cast half way between Mandalay and Amarapura, or in Ava, as well as in Pegu in the 17th / 18th centuries. It is possible that some of the wax used for moulding was imported from China. Up until the turn of century this was an important trade article for Szechuan and was produced by an insect, smaller then a pin head, very likely as a result of physical defect.
Sometimes, a weight from the mould would be too heavy – in this case metal was taken off the pedestal and, if necessary, the pedestal was actually hollowed and thus the weight was adjusted to the standard. If the weight was too light, threads of metal or small pieces of glass or lead were fastened. Many weights do not bear any gauge marks. The question then arises whether they were cast illegally, without official controls. Comparing the weights with gauge marks to those without, we can see that there is no difference between the two types as regards their difference to the standard opium weights.
The lack of gauge marks on brass opium weights is reasonable: most of them were cast unofficially after the reign of the Burmese kings and had ended and the Britain’s had introduced round iron weights.