Research and notes taken as of 12 October, AS LI.
I’ve been working with leather for most of my life, but until a few years ago it had never occurred to me how far the use of the pigments and dyes that we take for granted in modern leather work has evolved through the years. With that said though, it’s also somewhat disheartening to see just how far from period the same color treatments may be from the colors and finishes that actually did exist in period.
As an example, my by and large favorite “antique” process would likely not have been used at all, as the leather products that sit extant have antiqued naturally. Instead, it would have been more likely for a finished tooled hide to have been more of a uniformly dyed color, or let wax and/or heat treatment enhance the tooling itself naturally (in the instance of armor detailing).
What has also made things a little more difficult in the research process has been that the majority of actual documented processes seem to refer to the treatment and color of hides in full during what seems to be the tanning process. Since most of my hides are purchased after the tanning process has occurred, as it would have been likely to be the case within period, gaining the pigments to a full side would have potentially been something that had to occur before the actual creative process of the leather worker would have begun. Tanning and dying are both extremely stinky processes, and it is documented that both particular professions would have been held to the outside of town – whereas the actual leather working processes that would have occurred within other occupations (such as cobblers, armorers, etc.) would have had no issue being conducted within the town itself.
I started into the process of trying to get a more period aesthetic with color by research and recreation attempts against recipes found between Pliny the Elder and Maister Alexis of Piedmont. Both reference the full bath methods that did occur when curing and coloring a side, so attempts were met with weak results. As such, I have begun to consider the early results as inaccurate, though I have included them within these articles as a point of reference to what has already been attempted prior to my more recent attempts. I feel that the perceived failure in the early attempts has actually rendered itself useful, since I know that the earlier work did not get me where I wanted to be, I needed to shift gears instead of pursuing the recipes in full.
Since most of the methods and recipes that are found from period utilize water heavily within the dye creation process, I was curious to see if that mentality in and of itself was actually holding me back from getting the desired results. Since the currently available leathers have chemicals that are added during the tanning process, the water based mediums tended to act more like a mild stain than a dye, in that they didn’t thoroughly breech the epidermis (except in the instance of the vinegar black experiment, since it persists as a result of a chemical reaction between the oxidized vinegar and the tannins within the leather). As such, I hypothesized that utilizing a different base than water might permeate the epidermis. The foundation is based around the currently marketed dyes that are alcohol based, as they tend to absorb extremely well.
Changing Methods to Cold Leeching
I’m calling my current process “cold leeching”, though it may be called something entirely different by other people. In contrast to other dye methods that I’ve researched, I’ve been using no higher temperature than a constant 70-75 degrees (room temperature of my home) throughout the process. I’ve found that the actual temperature that’s been utilized in the dye making process can dramatically affect the resulting color of the vat, so I am currently attempting to only pull out what should naturally occur with time by “leeching” or pulling the color directly from the originating material.
I decided during my initial testing to go for a constant within documentable sources, that being brown. Since the tanning process itself utilizes plant medium in the way of tree bark, nut hulls and the like it was also the easiest method to reproduce. Since I have a number of pecan trees that are in my back yard, I gathered up two half gallon jars worth and placed them in the jars. All of the documented sources that I was able to find referenced black walnut hulls, so I was sure to gather up the nuts while they still had the green outer hulls intact. During the initial test, I utilized one batch filling to cover the nuts with vinegar and one batch filling to cover the nuts in rubbing alcohol. I chose the rubbing alcohol because of it being both inexpensive and close to the modern alcohol dyes that I am familiar with. The decision to use vinegar as my second base was due to the additional steps that are involved within creating mordent based dyes, since vinegar is often times used to lock in color.
Once the jars had been set up and the lids sealed on, it became a waiting game. I tested against pieces of scrap leather every three days for the first week, then each week thereafter for a two-month period. During the leeching process, the difference of note became that the vinegar turned a sickly green in color and looked to be moldy, whereas the pecans in the rubbing alcohol quickly blackened and the alcohol itself darkened very quickly. The alcohol result was what I was looking for, wherein it appeared to be expediting the natural deterioration of the husks and absorbing the color of the rot into the alcohol itself, whereas the vinegar appeared to be taking the course of a pickling process. At the time of straining, the alcohol base had thickened somewhat, but was almost black in color in the jar, the vinegar held pecans were still quite green. I decided to test the finished dyes on both leather and wood, as seen within the presented display. Both mediums accepted the alcohol base very well, but the vinegar seemed to repel from both. The alcohol base gave almost a commercial quality color as was intended, so I am quite pleased with the results.
About a week into the batch, I was excited by how quickly I was seeing results from the alcohol base, so I decided to see what results I would get from other mediums that I had on hand. Following the same process as noted above, I did smaller batches of alcohol base using dyer’s madder (as I had some left over from my initial experimentation) and a separate batch utilizing sumac berries (that were given to me from a friend during his foraging). Both dye stuffs reacted in a similar manner, where the cold leeching turned the alcohol base relatively quickly and the jars darkened with time. In the dye tests against leather and wood, the alcohol base absorbed quickly once again, though the sumac berries were a very faint tint (almost a blush color on paper). The madder yielded in an orange shade, which looks to be more evident on the wood than on the leather.
Results and Observations
The process in and of itself is simple, and easy to replicate. It is simply a matter of patience in letting materials soak in the alcohol to pull the colors out. The penetration of the alcohol seems consistent, so at this point I think that I have found a good combination of resources. I do think that the natural heat from the summer weather assisted in keeping the constant moving, so subsequent testing will likely have to be indoors in a climate controlled environment, such as a pantry so that the winter months don’t adversely impact the dye stuffs. In an effort to retain the colors that have come through so far, I’m also going to likely need to keep the dyes out of natural light, or bottle them in amber bottles so that the small amounts of light that do come into the shop do not weaken the colors.
Also, since the dyes are alcohol based, there should be a disclaimer for others that might want to attempt similar experimentation that the dye stuffs are highly flammable, and alcohol does absorb into the skin. Use of gloves will keep the dyes from penetrating the skin and causing damage. I have only been using the dyes in a very well ventilated area as well, since the fumes can be a bit much.
I am in no means done with the experimentation process. At this time, I think that I will be moving forward with different fruit mediums in order to compare results against my initial tests (elder and blue berries, then adding raspberries and holly berries to try and get a good red). Additionally, I will be testing against other green husked nuts that I’m able to find to see if I’m able to get a range of browns, similar to what is available for wood working projects (oak, walnut, etc.).
I am also looking forward to testing against other mediums found within the original sources to see if I can get an application of the tints that were referenced using the same methods of cold leeching. I also intend to test against different kinds of alcohol to see what the differences in residue and permeation will be.