Prehistoric glue making

In prehistory practically every material that was sticky enough could be used as a glue of some sort. For example, in theory honey could be used to glue some things that didn't need to be fixed tight, but knowing the fact that honey is highly valuable food it is not likely that it was used in those purposes very often.

Anyway, in this blog I wanted to describe to you two most used glue making techniques throughout prehistory, heating up birch bark and mixing pine resin and couple of more ingredients together to get efficient glue.

There are evidences that Neanderthals used birch bark pitch to fix their tools with wooden clubs even 200 000 years ago. Team of scientists from Leiden University experimented on that subject and managed to get birch bark tar by rolling it in hot ashes and got quantity necessary to fix what they wanted. By simply repeating the process over and over again they could get as much of the tar as they wanted.

According to Werner Pfeifers and Marco Claussens experiments that were published on Exarc web page, beside this simple method Neanderthals used there are two more methods for birch bark glue making. There is open distillation method and closed distillation method. They experienced without clay pots, but instead used animal skull as a tar collector.

By the open distillation method of birch tar making they used elders tree branch, hollowed to collect tar in a pot. Branch was fixed in the ground that way that one end is pointed to the place where bark was fired and other end was pointed into the pot where tar was collected. Above was put the bark and it was covered in thin layer of clay. After that large fire was made to heat up the bark. After some time fluid started to drain trough elderwood pipe and they got the tar.

Closed distillation is somehow different, because it doesn't let the air in the distillation process. In this method they dug out small pit in the ground, put skull on the bottom and encircled it with small stone pillars and on top of them stone deck that was pointed to skull. On top of the deck was put birch bark and covered it with grass, twigs and clay. Big fire was made, that burned 2 – 3 hours and then they let it cool down to prevent tar catching fire when they opened it. In the skull tar was collected and then they heated it up on small temperature (60 °C) to get pitch which is perfect glue for any kind of purpose.

Fig. 1 Tar in the skull after opening the closed distillation. (Pfeifers and Claussens experiment)

I saw this same technique being conducted, but using clay pots for containing birch bark and to collect birch tar. In the ground was dug out small hole. A bell shaped pot was filled with bark. Then pot for containing tar was put on the ground, bell shaped pot was put on it upper part of pot pointing down to container. Pots were covered with dirt and small fire was made. The result was the same, tar was produced that way.

The second way to make glue is using pine wood resin and is quite easy and efficient. This method I used myself so I am simply going to explain what I was doing during the process. There are few different types of pine resin glue. You have one with resin and charcoal, then you have the one with resin, charcoal and bee wax, also you can mix resin and bee wax only. Instead of charcoal, ocher and chopped balls of dried rabbit feces can be used as a binder of the glue.

First step is to collect all the material that is necessary for the glue. You need to find pine wood forest and start picking resin of the trees. Usually there is a lot of resin on trees and you simply scratch it of the tree. After you collected the main ingredient for your glue, you start looking for honey bee comb. In modern life that ingredient is much easier to purchase by a local beekeeper, but in prehistory I imagine that wouldn't be very pleasant job. The third ingredient you can simply take from any fire that was made, the charcoal.

Then you need some kind of container, I always used clay pot, but in times before clay pots I think that containers such as skulls could be used, or they could heat up the ingredients on stone too.

Fig. 2 Ingredients for glue making, pine resin, powdered charcoal and bee wax

First you need to prepare the ingredients. The one ingredient that needs preparation is charcoal, it needs to be smashed into fine powder so that you can mix it with the resin. Then you need to start a fire. Put three parts of resin and one part of bee wax in pot and put it on small amount of heated coal. Then after it gets liquid put one part of powdered charcoal in too, mix it properly, but watch out that resin doesn't boil because then it loses it's properties. After that you can leave the glue in the pot and let it cool down, but that is not practical when you need a small amount of glue because you need to melt it all. That's why it's better to put the glue on some kind of stick and then you can melt just a small amount every time you need it.

Fig. 3 Applying glue on wooden stick

As I said in the beginning, practically any material that is sticky enough could be used as glue. For example there is starch, which is made by mixing powdered wheat and water. Then you can make glue from raw animal hide, such as cow hide. Also there are lot of materials in the nature that can be picked and be used as natural glue, such as Blue Bell plant, whose underground bulb is naturally sticky, and wild cherry sap.

Today we are privileged with all the wonders of the modern world, we don't need to think of how something is made, we just buy it and use it. But in prehistoric and historic times people were much closer to nature and could use every part of it. By simply exploring the world around them they came to solution for their hafting problems, they literally invented glue which many generations after them used for their tools and weapons, and which very much helped in their survival skills.

Also see:

https://exarc.net/issue-2015-4/at/experiments-possible-stone-age-glue-types

https://www.newsweek.com/how-neanderthals-made-tar-glue-weapons-tools-657594