How were kettles made in the past?
Taking a good look at the older timpani that still remain in Europe, we can see that there are seams on the sides and near the bottom of the kettles, and that the thicknesses are all uniform.
Considering this, we can see that the timpani were made by preparing two fan-shaped copper plates for the sides and a round plate for the bottom, after which they were bent together and attached. The bottom plate was beaten and shaped into a bowl separately, and the side plates were stuck together to complete the overall form. As with modern-day hammered kettles, we can envision the craftsmen of the era putting their hearts into beating the kettles into shape.