Based on 'Rock glazes of NZ' Minna Bondy
Sample 89. Sand near Nelson
Principally quartz and feldspar (mainly microcline) derived from granite
The glaze would be perfect for someone wanting to achieve the effect of lichen😉.
This project has been an unravelling of knowledge. The detective work continues as I piece together vague descriptions, such as "Sand near Nelson" with the results.
Bondy's result reads "Clear blue-green celadon" which I definitely did not achieve, this could come down to a few factors.
The Nelson area has always been a haven for potters, the surrounding geology is rich in ingredients such as Quartz and Feldspar in the form of granite. The beaches are deposits from rivers that carry weathered particles downstream, grinding them along the way, the silica being the hardest mineral is what is usually left behind in the highest quantity. The bubbling could be from high deposits of shell material in the mix.
The sands of Kaiteriteri beach "near Nelson" are much purer silica and although I didn't sample this sand with the Bondy samples, I did test it in the kiln and it produced a lovely white melt. So I will grind this more and retest it, following Bondy's methods.
I will also retest the Tahunanui sand after grinding it longer and sieving through a finer mesh. I'm sure a trained eye will be able to decipher this test and perhaps with a bit of tweaking I could achieve the blue/green celadon that Bondy describes. Or perhaps I was just sampling the wrong material from the wrong "near nelson sand"