Glue Testing

I tried to set up an experiment to test various kinds of Mesoamerican glues. I bought the ingredients and made up the glues. Using each one I glued a piece of obsidian to a piece of wood. I then had the plan of hang weights from the obsidian until the two seperated to determine the effective binding strength. To add weigth I hung a bucket from the stone and gradually added sand, trouble is some of these glues are so strong. I ran out of sand and the stuff was still holding. I have 7 kilos of sand and I was only using 1g of glue.

So any ideas how to conduct a glue test, please?

Well, you could use a hydraulic press with a pressure gauge. Record the pressures in PSIG then convert it.

We do the same when measuring tensile strength in bolts which require a considerable amount of force. Also, you would be able to measure the shear load as well...

In the end I thought another bag of sand would cost less than a hydraulic press. One of the glues held over 22 kilos.

I put the results on the main site.

Sorry about that. I guess it is one advantage of being a grease monkey is having access to tools...

At 22+ kilos, that was a shear load correct? That is very impressive, given that the load may have been shared with adjacent blades.

Is there any ethnographic evidence that composite glues may have been used? With such a marked increase in strength, I doubt it would have gone unnoticed to the original makers.

Does increasing cure time have any affect?

Whoops I meant to write pounds. Few mistakes on the main article too. I thinks it's correct now.

The compounds predate the Aztecs by thousands of years, worldwide.

Have you ever used the swim bladders of sturgeon (Isinglass)? In alto california at least, swim bladder glue was used in many instances (i.e. Yurok bows). I would really like to see how it holds up.

However, prep for the glue is to chew the bladder, mix it with saliva (amylase maybe?), and spit it into a container. Supposedly, it will last for months- all you need to do is warm it up again...

why are you testing the strength of the glue in this manner? What are you hoping to gain?

Hi exparch,

Testing the tensile strength of the adhesives is many-fold. For one, you can gauge how much abuse (through normal use-wear..or not ) the tool can handle or is capable of..of course supported by data of actually using it. However, this will also help determine if you used the right amount and at a good location (again basing off of ethnographic info and what is found in the archaeological record if possible).

Secondly, this can also lend to inferences to possible selection of adhesives--as one of the probable key factors. Strength of the glue may have determined its use, but also availability of components, the processing time, and how the product holds under certain conditions (ie the fish bladder adhesive mentioned above is strong but poor in humid conditions), etc. All of these factors (and more probably) may make a great (strong) adhesive not worth the time and labor requirements, particularly when the second or third best would work just fine.. again speculative and needs to be supported my a range of data... (ethnographic, archaeological, experimental, etc)

So, testing the glue in such a way is necessary, but is possibly only one of many factors that need to be addressed. Ultimately, it's up to your research design...

Goban