Medieval Polishing Toolkit

by Jamie Hall on May 10, 2010

The finishing of jewellery and other precious items is one of the most important stages in production – the finisher can validate the hard work of the manufacturers, or ruin the fruits of their labour. “Finishing” is such a broad term, and this post won’t attempt to cover all the processes that were used, and are used; instead it will look at the tools available. All references are to chapters from On Divers Arts by Theophilus, in the format “Book-Chapter” – eg. III-2 is Book 3, chapter 2).

When the finisher receives an item, be it forged or cast, there are normally tool marks and other imperfections that cannot be shown to the customer (you might know that first hand, if a customer has ever demanded to see a work-in-progress). In the modern workshop my first step is usually to pickle the item, to ensure that there are no glassy or chemical residues that might interfere with finishing. In general, the cleaner the item is at every stage, the better the final look of the piece. We’re lucky to have strong acid and ultrasonic baths, but the medieval finisher would have to rely on soap and boiling water. If they were removing glassy flux residues, they would have to use abrasion, or else soak the items in weak acid for a long period.

Having removed surface contamination, a coarse abrasive is used to take out file and graver marks. At work, I might use a flex-shaft or a polishing lathe for this, but generally I use 3M Imperial Microfinishing film, in sheets, or as sticks that I make up myself. The concept of a micron-graded abrasive bonded to a plastic sheet is quite a recent innovation, but the same concept can be done with more rudimentary materials. The first thing is to have a surface, like leather or fabric, which can be wetted with oil, water or spit, and then sprinkled with a powdered abrasive mineral. So long as a small amount of liquid is used, the surface could be in strip form, so that the workpiece is gripped in a vice, and both hands used to move it back and forth. For the polishing of stones and suchlike, Theophilus suggests a flat unglazed tile as a surface, or a sheet of lead. For very deep marks, a piece of actual mineral could be used as both the abrasive and the implement for applying it.

Burnishers and scrapers are mentioned at various points (eg. III-26, III-42), and these are the real polishing method; the buffing of the item seems less significant than it is in the modern day, and there is certainly no expectation of a mirror finish (thinking of which, I should look into the history of polished metal mirrors). Files also play a part, as do the hones (whetstones) that are used to sharpen the scrapers and smooth the burnishers – they must be well-polished themselves, to leave a good finish on the metal.

There are some mentions of mechanical assistance – III-81 makes a vague reference to a grindstone, and III-85 discusses the smoothing of bells on a lathe, using a piece of sandstone. Otherwise, everything is done by hand. As a rule, for any item that has been pre-finished with well-dressed, clean tools, Theophilus suggests buffing – die-pressed metal is cleaned with fine charcoal and then fine chalk (III-75), and gilded brass is cleaned with a brass scratch-brush (III-68). The same applies to chased, engraved and planished surfaces. On the other hand, for items that aren’t pre-finished, a course abrasive like sand is used first, as is suggested for the cast censer described in III-61, or cleaning holes in gemstones using sand and a copper pipe (III-95).

There are only a few substances that are listed for polishing and buffing – charcoal, chalk, sand and sandstone, as mentioned above; bone is polished with sifted ashes (III-94) (presumably to prevent any grit), and III-95 describes polishing stones with their own dust. Emery is also mentioned in that chapter. The least pleasant is earwax, as a final finish for niello (III-41) Implements for applying the abrasives are generally cloths or leathers of various types, pieces of abrasive rock, and even a stick with a shredded end (III-61) for the cast censer.

I’ll need various scraps of leather and cloth, different types of wood in stick and block form, abrasive stones, mineral powders and oil – I can supply my own spit, water and earwax. I’ve found a bag of rottenstone (tripoli), from L. Cornelissen & Son in London, who also supply a wide range of other substances that I need.


Jerry Fowler May 11, 2010 at 01:15

Ear wax, wonderful stuff you know, only a smiddgen of it will kill the head on your beer. I know you were just waiting for that bit of knowledge.
I always enjoy reading your blogs, thanks

Jamie Hall May 11, 2010 at 07:36

How did you find that out, exactly? Dare I ask?

stuart bowie February 11, 2011 at 02:45

a smooth stone such as ` water of ayr stone` (its what I knew it as. ) Is handy and used ( along with spit or water if preferred) after fine emerying and before burnishing. normaly used on metals. handy for taking out fine scratches too.

Jamie Hall February 11, 2011 at 19:51

Thanks for your comment Stuart. We do have some water of ayr stone at work, and as you say, it’s excellent stuff. I’m fond of it for getting into funny corners, because of the way it disintergrates.

I did some research on it when I was writing this article, and there isn’t any clear evidence of the stone being used before th 18th century; that isn’t to say that it wasn’t used – but if it was, it was probably localised use.

As almost everything is abrasive to something, there are bound to be lots of minerals used in areas where they were found near the surface; once people start deeper mining, that suggests that they need enough of the mineral to trade; an interesting subject for the future, perhaps, but too complicated to go into for this article.

Comments on this entry are closed.

{ 1 trackback }

Previous post:

Next post:

WordPress Admin