Islamic brass makers were more advanced than their western counterparts

Inventions 23 Apr 2021 Contributor
brass in Astrolabe
Astrolabe was used to understand the height of the celestial bodies in the middle ages. Photo : Dreamstime

We often get flabbergasted seeing old historic structures and monuments. Not only they are marvelous to watch but the engineering brain behind them was ahead of their time. If you heard about the Mehrauli iron pillar at the Qutb complex, you would be surprised to know that this 1600 years old pillar is rust-resistant. A new such kind of engineering gem was understood when a Ph.D. researcher, Brian Newbury, from Lehigh University examined the 17th-century astrolabes fabricated in Lahore. He found that the brass used to construct the same was produced through a melting technique that was developed in Europe more than 200 years later.

Astrolabes in Islamic history

Astrolabes are instruments, designed for astronomical calculations, time measurement, performing surveys, determining distances and direction on land. They were introduced and actively used in the Islamic world from 700 A.D. to the mid-19th century. They were used in Europe from 1000 A.D. to mid 17th century. Astrolabes are constructed using thin metal discs, mainly of brass, stacked on top of each other. Researchers believe that zinc (a crucial component of brass) was produced in India long before the 1600 century and they also believe that zinc was re-oxidized and used to make medicinal salves. According to Brian, “In Zawar, India there has been proof of production of zinc as early as in the 13th century”

What did we learn from the study?

Brian presented this study at the British Museum in London and at the Adler Planetarium where he described that the brass used to make the astrolabes were produced from a ‘co-melting’ technique. Using the Advanced Photon Source Synchrotron at Argonne National Laboratories in Chicago, alloy composition was identified by x-ray diffraction. It revealed that the brass astrolabes contained 39-45 weight percent zinc which was almost impossible to achieve using the traditional brass-making methods known by the European metalworkers.

Making a thin brass sheet of 1 mm is very time-consuming and the cementation technique, developed by the Romans and known to many, can not achieve more than 32 weight percent zinc in brass. It is believed that the Islamic metalworkers used to make brass by first producing zinc through co-melting and then melting it with copper again. Above 35% zinc, the color of brass changes and it also becomes harder and easier to cut. This helped the craftsmen of the Lahore astrolabes to engrave finer details and produce a more accurate instrument. This co-melting technique was only introduced in Europe in the 19th century.