By Lady Caoilfhionn inghean ui Magil Ruanaidh Various types of glues made from natural products or by-products have been used for literally centuries. One book written in the 9th century called Mappae Clavicula describes how to make cheese and hide glues. On Divers Arts was written in the 12th century by an author by the name of Theophilus who also wrote about cheese and hide glues, added instruction on fish glues and some vegetable gum adhesives. In the 14th century, Cennino D‘Andrea Cennini wrote Il Libro dell‘ Arte also known as the Craftsmans Handbook. Cennini‘s book covered much the same information and recipes that was in the other books. These recipes have been handed down through the centuries and in many cases are still being used today. Hide glues are still used in woodworking, the preparation of vegetable gum adhesives are still being used by artistic painters and parchment and fish glues are used today by people who work with gold and silver leaf. The glue that I was interested in making was what is considered a collagen glue or hide/parchment glue made from rawhide or parchment scraps and would allow me to use supplies already in my workshop or given to me. Also, I was interested in knowing if it would allow me to glue leather to leather or leather to wood since I have not been able to find documentation on how or what was used to glue down leather in period. I did find it interesting to find from the reading that I have done that, "various strengths are determined by what type of hide it is made of and how much water is used in the preparation" (Heath pg. 19). The translation from Cennini‘s book , The Craftsman‘s Handbook, states: And there is size which is made of the necks of goats and sheep parchments, and the clippings of these parchments(sic); these are washed thoroughly, and put to soak a day before you put them to boil. Boil it with clear water until the three parts are reduced to one. And when you have no leaf glue, I want you to use this size for gessoing panels or anconas; for you cannot get any better one anywhere. The modern instructions say to take an ounce of parchment or rawhide clippings and a gallon of water and boil for 4 hours. The pot that I bought to be dedicated to glue making will not hold a gallon of water at a time. My answer was to keep another pot full of water simmering on the stove to add as needed to keep the solution boiling for the hours needed. Once the parchment scraps were boiled for the 4 hour time period, I let the glue thicken and tried the 'sticky finger test‘. This is when the fingers stick together strong enough with the glue on them to have to pull them apart with a little force. I then poured off the glue through cheese cloth and a sieve, leaving just the glue to cool and congeal. I placed the glue in a glass pie pan and let it stand over night, the next day I peeled the glue from the pan and let these pieces dry completely. I broke up the dried glue and stored all of it in a glass jar with a tight lid, this keeps the moisture out of the jar and allows for a long storage life.
I have used the glue on trial basis
only, gluing silver leaf to leather,
leather to leather, and leather to wood. Taking a small pyrex dish I put in the glue chips,
added approximately a half ounce of water, then sat it
on an old warming tray and made sure the glue did not heat over the 140o mark, stirring to get it to desolve. I found that the glue needed to be a different concentration depending on which medium was being glued down. The concentration that would allow me to glue down modern silver leaf would only soak into vegetable tanned leather and eventually cause the leather to stiffen. When I allowed the glue to condense down and thicken, I was able to apply the glue to both parts whether it was leather or wood and let it dry until no longer glossy, then apply a second coat, put the pieces together and weight it down until it was semi-dried and held. The first coat of glue acted as a sealant to the pores of the wood or leather, the second coat allowed for a glue to glue bond. I have used this technique with modern cements to get a very tight bond with leather I do not want to pull apart. Also after the test pieces dried for about 24 hours the glue bond was flexible and did not try to peel apart.
After scanning through the book of adhesives, I decided to go and get a pot, a thermometer and some spoons I could dedicate to making the glue without using good pots and pans. Ok- I was ready to start. I had goat rawhide scraps (an ounce of them), my new pan, spoons and a candy thermometer. About 2 o‘clock on a Saturday afternoon I began. First mistake- I didn‘t pre-soak the parchment scraps. Second- I had misread the instructions, or maybe I should say that I miss interpreted. The instructions told me to ―Boil parchment scraps and clippings in water for 4 hours. The water should be kept at a boil not over. If the glue is heated to more than 140oF (60oC), it begins to break down and lose its strength.‖ I read this as saying Do Not let the water get over 140o. For those of you that cook you know that water boils at 212o, 140o is barely a simmer. About 6 o‘clock that night I realized that I have done something wrong and go back to the instructions. It was then I understood that the instructions were in two parts. 1. I should have been boiling the scraps at a low gentle boil for 4 hours. 2. When I was to use the glue I wasn‘t to let the mixture over heat past 140o. Third mistake- I turned the gas up to get a very slow boil and then went and watched a movie. You guessed it. About 10 that night I hear a snapping and popping. Oh, S—t!! I rush to the kitchen to find my glue drying to the bottom of the pan. Off went the gas and I pour about a cups worth of water into to the pan, thinking that this project was completely ruined. Luckily it never got to the burn stage and the pan was not even scorched. Adding the water was probably the best thing I could have done, coming back about a half an hour later I found that the glue had loosened and nothing was sticking to the pan. At this point I decided to see if I could salvage anything from what was left. I strained the mixture, first through a wire strainer and then through cheesecloth, then cleaned the pan. Then I returned the mixture to the pan, heating it just enough to condense it down to a thicker consistency. It was then poured into a glass pie plate, and it sat overnight. The next morning I had something that was like a tannish looking jello, from the reading that I had done I knew that this was my glue and that I needed to peel it off the glass and let the pieces dry completely. So now I have a small little jar of glue chips ready to use. You know, there is a perverse enjoyment in talking to someone who is not in the SCA when they innocently ask you what you did over the weekend… "Oh, I made glue..." Bibliography and Sources: Campbell, Gordon. The Grove Encyclopedia of Decorative Arts: Two-volume Set. Oxford University Press, USA, November 9, 2006 Heath, Maya. The Compleat Anachronist: A Practical Guide to Medieval Adhesives. Issue No. 134. First Quarter 2007 Replication of Gilt Leather-Reconstruction of the Decorations from Callendar House, Scotland Department of Conservation, Academy of Fine Arts in Cracow, Poland, ul. Lea 29, 30-052 Cennini, Cennino. D‘Andrea Il Libro dell‘ Arte: The Craftsmans Handbook. Translated by Daniel V. Thompson Jr., New York, Dover Publications Inc. 1960 Theophilus, On Divers Arts Translated by John C. Hawthorne and Cyril Stanly Smith. New York, Dover Publications Inc. 1979 Jamison, Alexander. A Dictionary of Mechanical Science, Arts, Manufactures and Miscellaneous Knowledge. London. Printed for Henry Fisher, Son, and Co. 1829 |
