Weight or VOlume? A study of bronze covered iron weights

Abstract

Until lately the bronze clad iron core weights evidently in every day use at market places in Sweden, like Birka and elsewhere, have been judged almost only by their weight.

As the weights have corroded, sometimes badly, during the many hundred years in the earth, this is not a very good way of estimating their true weight and to ascertain the weight system used. 

Kyhlberg in 1980 pointed to the fact that the ball shaped weights retained their form for a much longer period than their weight.

His ideas have been developed when studying a new weight find from Häffinds, Burs Parish, Gotland. 0ut of some 40 ball shaped weights, 15 could be measured and calculated using simple geometric mensuration formulas.

The main weight system was found to be based on a "Unit weight ¹¹ of 4.19 ± 0,02 grams (Standard error).

Similarly a few weights from Björkö were found to belong to a system based on a 3.97 ± 0,03 grams "Unit weight".

The systematic errors are still difficult to estimate, but the figures are believed to be accurate within ±I% or so. - Further studies are being planned.