For the past five days, Beth and I have been staying in the Park Campus of the University of Northampton taking a course on historical leather offered by the Leather Conservation Centre there. Along the way, we’ve had the pleasure of exploring the city of Northampton (which, through extreme trial and error, we discovered has three separate bus companies), and learning lots about leather. We thought we’d share with you some of the experiences that we’ve had during this journey!
The course itself covered a variety of topics ranging from the chemistry of the tanning process (which I was incredibly interested in) to species identification through examination of hides (which Beth found particularly interesting). I think one of the coolest parts of the course was that we actually had a practical component where we participated in all of the processes that go into making a piece of leather. While I could spend a week (and the people at the LCC have) talking about leather, I think it would be prudent to focus on the tanning process itself, something that both Beth and I didn’t know too much about prior to arriving here. There are three main processes that go into creating a piece of leather: 1. Beamhouse 2. Tanning 3. Finishing. I’m going to tell you about these in a bit more detail
The name “beamhouse” comes from the fact that several of these operations were performed over a large wooden beam. The purpose of these processes is to prepare the raw hides for tanning. This involves first salting the hides to prevent putrefaction, defleshing to remove the extra flesh attached to the skin (that was probably the grossest part), unhairing, liming to breakdown unwanted proteins, and then pickling and bating to reduce the pH and to clean the grain. All in all, beamhouse is some of the nastier parts of this whole process. Nevertheless, we still took part and here is a video of Beth defleshing and a picture of me unhairing a goat skin hide.
It’s really quite amazing to see the difference each process makes, though I will refrain from more pictures in order to reduce your nausea. At least you can’t smell it, but we could!
This is the part of the process that prevents leather from decaying like normal skin would. It is a chemical process that fundamentally changes the structure of the proteins and is often hard to reverse. The hide is put in a drum along with a specific tanning chemical. There are several types of tannages that can produce strong or soft, rigid or flexible, aesthetic or durable leather (chrome tanning, alum tanning, wet white tanning, etc…) but the one used historically was vegetable tanning where natural tannins (found in bark, teas, and plants) were mixed with the leather for long periods of time. This interested us historians the most and that was what we tanned our hides with. We then sammyed the leather (pressing out the water) which created a firmer, leathery type hide, and then split or shaved the hide to the specified thickness. The leather was then dried briefly by a vacuum drier and then slow dried by toggling where they were hung in a low temperature oven by toggles.
FINISHING AND CURRYING
This part of the process is the final bit that makes leather look like what we buy in store. First, you can oil the leather set it to soften the leather and add some flexibility. To help with this, you can stake the leather where you rub it over a blunt edge to add more flexibility and softness. The next part can vary depending on your leather’s destination but there are multiple options. You can dye the leather, buff it which sands the top of the grain creating a suede feel, glaze it using a very scary but cool machine to give it a shine, and emboss it with beautiful patterns. These last few are often where extreme skill and artistry separate the quality of leather finishing.
All you have left is to cut it to your fancy and use it for a shoe, a bag, upholstery, or as I have done, a wall hanging with your name on it:
I can say that by the end of this course, Beth and I probably know more about leather production than we ever needed to know but it was such a fun, educational, and engaging course that we thoroughly enjoyed it. Even though a lot of the practical lessons were done with modern machines, the principles of tanning has been consistent for thousands of years and having this understanding helps us understand how tanning may have been done in the Ancient world and at Vindolanda. By understanding historical practices, tools involved, chemical reactions that occur, and the necessary environmental conditions, we can perhaps take this knowledge and apply it to the amazingly preserved leather that we have at Vindolanda. This week was definitely time well spent and I also greatly appreciated the opportunity to spend it with one of the best professors!
Be sure to keep checking the blog for updates about the progress of our trenches!
If you have any questions about specifics of the processes discussed above, feel free to comment below and we’d be happy to clarify a few things. (Once again, apologies for the long post)