For a while now I’ve been interested in experimenting with the possibilities of Volcanic Ash. My last post alluded to my research into the possibilities of high silica ash that I’ve been processing myself. Like most of my testing, I like to cast a pretty wide net of different potential recipes and gradually zero in on interesting effects and variations. In the process of varying the types of clay in my West Palm Ash recipe, I also experimented with the proportion of ash to feldspar and remembered that in some cases Volcanic Ash can be a 1:1 substitute to feldspar. On a whim I chose to finally test some Volcanic Ash in my recipe. The results were pretty stunning! Having thrown a bunch of darts now and nailing the bullseye, my next round of tests will further explore the potential for this material! Stay tuned, as I’ll be posting all of my tiles from the last few firings!
A picture of the eruption of Mount Saint Helens in 88′. This is where the stuff comes from, and it’s easy to see while the material itself isn’t technically an ash in the traditional sense of the word, the name sticks. The following pictures are closer images of what this stuff looks like under microscopes.
The foamy, almost bubbly texture of pumice happens because of simultaneous rapid cooling and rapid depressurization. The depressurization creates bubbles by lowering the solubility of gases including water and CO2 that are dissolved in the lava. This process causes the gases to rapidly exsolve. It’s like the thing that happens when you open a can of Dr. Pepper! Add that process to the simultaneous cooling and depressurization , and you have ash or Pumice with an interesting bubble matrix!