Marl Lake: Preparing Maya Blue


Since I began this project I have been pining for a good blue to use in my work. Growing some woad and thereby having indigo to use was a wonderful start.Certain concerns, however, were always in the back of my mind as to whether such pigment could really be counted light-fast. So I kept on playing with different ideas of what might be possible within my 100 mile limit …

Then the idea struck me: What about “Maya Blue”? About 800 AD cultures of the pre-Columbian Mesoamerica, such as the Maya and Aztec, discovered how to create a bright permanent blue. But, this technology was lost and it wasn’t until the 1960’s that research began to uncover how this pigment had been made (this research is still underway today). What became clear through this study was that the blue was made from two materials: Indigo pigment and Polygorskite clay.

The question was, could I find polygorskite clay? Here again, with my gratitude, Reiner found an old reference that mentioned Marlstone, a lime-rich mudstone, oftentimes has some polygorskite in it. Further research indicated that the ratio is usually 35-65% clay and 65-35% carbonate. The hope of creating one of the great historic pigments of North America was very inspiring. Reiner, Maggie and I decided to head off to Marl Lake, a man-made lake that was excavated in the early 1900’s.

Unlike most of my other excursions, Marl Lake is not a rural or industrial setting but a recreational space with lots of cottages. I was prepared to introduce myself and the project to different cottagers if necessary, but it turned out not to be needed. Our initial look was worrisome because it appeared that sections of Lake Rosalind (the adjoining body of water) had been back-filled. When we stopped by the side of Marl Lake to look around, however, Reiner found that this shoreline was pure marl mud! Within a few minutes we filled a pail and our search was over. While this cut off our usual enjoyment of exploring an area in more depth, such a wonderful find is really enough in itself. So, we headed home, enjoying our success.

At the same time that I was creating my indigo pigment I thought I should also get things underway in purifying the Marl I collected. What I really wanted to have from that Marl is a clay-ish mineral called Polygorskite. The other part of this marl is calcium carbonate which I can dissolve quite easily using a bit of hydrochloric acid.

So, putting some clean marl into a bucket I began to add the acid a little at a time. This resulted in lots of foam initially, but little by little it subsided. In the end what was left over wasn’t nice and white but a middle grey colour! Still I have no doubt that this is the polygorskite I wanted. This colour is known to exist for the mineral and it has a leather feel that is characteristic.

It will be very interesting to see what effect this deeper shade has on the final Maya Blue!

Maya Blue is a really interesting pigment. By itself, the blue of indigo darkens to black over time but once this plant material is embedded into the polygorskite clay, the results are amazing permanent. Instances of Maya Blue used in the harsh weather conditions of central America have not faded since their application in over a millennium!

I found that the best way I could mix them together was using my muller, but if I hadn’t broken my mortar and pestle I suspect that would have worked well too. It wasn’t hard, and the results are a good colour (something I was a little worried about, given how dark the polygorskite I found was). Now that I’ve mixed them together all that remains is finding the right roasting temperature and duration to create a durable pigment but keep it blue …

In researching a little bit about how Maya Blue is thought to work, I came across a really interesting site that uses cookies to explain. Take a look at:

The final step in making the Maya Blue pigment involves heating it. Without this step, the indigo pigment does not gain any special durability. When I was reading about this process, I was surprised at it’s implied simplicity: Mix together and heat. However, something that I am finding out is true for many of these processes is that colour achieved depends on very small variables. An extra hour in the kiln, or 25 °C of heat, can make a significant difference in the end.

It took many attempts to create the blue colour I wanted. But, in the process I found that making Maya green, on the other hand, is quite easy! Batch after batch I saw a slow progression toward blue-ness. My breakthrough came about 4:00 am when, not being able to sleep, I composed a graph of every article and report I had collected on Maya blue. From this I gained a better idea of where good colours might be found inside a set of reasonable limits.

A few more series of test crucibles were needed to really nail the colour, but I could see right away that I was on the right track. As a final test I subjected my new pigment to acetone which normally dissolves all forms of indigo. The clear liquid that resulted means that I have created genuine Maya blue and that I have a very special colour to use in this project.

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