For 7 years now I have been thinking about all aspects of how medieval craftsmen made objects out of bronze or pewter. The method of manufacture of some objects is obvious, from the excavated stone moulds for pewter badges through to the methods of making bells, which are recorded in detail in the 12th and 16th centuries, with nothing much changing in between.
But that still leaves some items unaccounted for. Some, like small bells, are made of sheet metal or else have cores of sand and clay within a stone mould a bit like that for making bullets, but nobody has left instructions for their manufacture.
Others, like mortars and pestles, well, eventually I worked out that they were probably made the same way as bells, and lo and behold, in Biringuccio’s book it says that you make mortars, basins and other vessels which need to be hollow in the middle in the same way as bells (page 268 of the paperback Dover edition).
This means that a founder needs a lathe of sorts in order to turn the core of the mortar.
I did in fact first try to make a mortar by having a wooden pestle and a mortar made, which could then have the earth pressed around them before removing them and sealing it all together, but that proved to be harder to get right than I thought. The pestle I did produce had a lot of flash down one side because the dampl clay was not rigid enough to stay perfectly in shape when I was taking the former out, and the mortar mould has not yet been tried due to the slowness of mould manufacture and drying and issues with melting the metal.
Anyway, what did lathes look like then, of the sort I can use?
Fortunately there are pictures and descriptions, but never enough.
Theophilus, writing in the 12th century, described two types. One for turning the clay core on for making a censer, which is basically two upright posts a set distance apart which have an iron spindle stuck through them. You can see similar designs in later medieval illustrations, listed below. That for bells is similar but uses a large wooden spindle with more woodwork around to support the weight of the damp clay.
The Mendel Hausbuch has a 1425 picture showing a pewterer turning a cruet or similar on a wheel:
It obviously needs a second person to do the work, but is interesting. It is obviously before they thought of adding a big wheel, which presumably gave some advantage in speed and control. The advantage of this sort of arrangement compared to that which is used by woodworkers is that it only rotates in one direction.
This one shows a 15th century turning bench, from the Wolfegg hausbuch, but it is turned by a handle at the end:
More like that for a wood turner? Certainly strong, and operated by one person whilst another turns the handle.
From the 1568 book of trades, of German origin,
shows a man with a turning lathe, it seems to be operated by an early form of belt, in the form of string, which goes round a much larger wheel turned by another man behind him. This appears to be an innovation of the late 15th/ early 16th centuries, and could obviously give you greater turning speeds due to the differences in wheel size, more like a modern lathe. Exactly how much better for the purposes of carving moulds and finishing off work is unclear and would take some experiments to be sure of. The issue with this illustration is that it appears to use large iron rods to hold the workpiece in place and to rotate, without any precise support, which is unlikely, and you can only see the great wheel behind, not the smaller one attached to the rotating iron rods. Also, whilst there is surely some artistic licence in this picture, I do think the large windows would be part of any such working place because of the lack of artificial light.
The type used for large bells appears to be like this:
A 1680 picture though shows part of such a wheel:
So it appears the same technology was still in use in the 17th century.
Lionheart replicas draws attention to these pictures:
An SCA persons woodlathe setup, inspiring my thoughts.
The tricky bit is working out the size, shape and making of a replica continous wheel for finishing moulds and carving wax out of objects made on the lathe. I suspect it would be best to have one with a great wheel, and 2 vertical posts 3ft high by about 8 inches wide, with a large heavy cross piece near the top. The main work area should be, given what I want to cast, about 18 inches long at most and have a radius of workable object of about 4 inches or so. Then it’s a matter of getting iron and wooden spindles. Spindles are mentioned in York foundrymens wills, so it is certainly appropriate for them to be used. Page 87-88 of English medieval industries talks about spindles and moulds, for potters and others, so it seems possible that pots and such were also made by lost wax, but then that would obviate the need for chaplets. But there are plenty more pot like objects than just cauldrons. Such as brass flagons.
The really useful thing though about such a lathe is that it would also be useful for finishing off the cast product, i.e. answer the questions I raised in an earlier post about how they got their items so nice and shiny. (https://medievalfoundry.wordpress.com/2015/02/09/finishing-the-casting-off-so-it-is-nice-and-shiny/)
On page 374 Bringuccio mentions putting pewter objects on an iron axle turned by hand and the application of a tool with a cutting edge to finish them off, burnishing them.
Page 219 of A History of British Pewter by John Hatcher and T. C. Barker says “The softness of pewter enable small items to be turned on primitive machines more suited to wood, but heavy items required stronger and more efficient lathes, and the imparting of a smooth finish without undue effort required an advanced form of drive which turned the article continously in one direction.”
They also mention on page 214 the inventory of a Rouen pewterer in 1402, which includes 14 turning tools, cores and mandrels and a lathe. The 1569 inventory of Henry Greene, a pewterer and bell-founder of Worcester, mentions a great wheel with 3 spindles, other spindles, a hollow ware wheel and related tools.
Basically the answer to my questions awaited only further research, I have had the information available for years. Which is one of the purposes of this blog, to help focus my research. When I know the topic well enough to write a blog post, I also know it well enough for any other purpose.
Now, how to get or make a lathe and associated wheels?