Armchair Potting

The development of clays by the natural process of weathering of igneous rocks takes a very long time. Some ceramic researchers-geologists suggest 200-300 millions of years and more.
We can be certain about the age of some of the ball clays (secondary clays transported and deposited by water) found in England which can be carbon dated to approximate figures of 150-250 millions of years. They contain organic impurities, for instance, pollen (source of carbon) picked up during their transportation.
The primary clays have no organic impurities and therefore it is not possible to establish their "date of birth". The origin of the primary clays is the igneous rock i.e. pegmatite, granite, basalt, feldspar etc. The rocks are subjected to weathering by rain water (may or may not contain carbon dioxide) from above and by hot water vapor and chemical gases from the earth interior.
It is mind boggling to think that it takes so many millions of years to turn the rocks into clay.

And now let's do a little experiment and see how long it will take to turn a rock, for example feldspar, to weather in to clay. Get a lump of feldspar 2-3cm across and break it in half. One half you cover with water and bring to boil in a saucepan and simmer for 5 hours and than compare it with the other half. You will be very surprised to see that the 5 hour boiling test produced a reasonable result. The surface of the break will be dull with considerable damage (weathering) just after 5 hours!!!!!
Imagine if you boil it for a year you should have enough clay to do a shrinkage test. It is hard to believe the entire scientific world talks such rubbish (tongue in the cheek) saying that it takes over 200 million years.
What do you think?
I bet you have never read such a suggestion that it takes only very short time (from just an ordinary person like me).

To test crazing resistance of glazes we subject a glaze sample to an autoclave test i.e. the sample is subjected to high pressure at elevated temperature for 1-2 hours. When cooled, the glaze sample is removed from the autoclave and inspected for crazing. And now what happens to a lump of feldspar if subjected to a high temperature and pressure in an autoclave for, just say, 5 hours? You guessed it - the lump of feldspar is covered with enough china clay which can be tested by a simple loss on ignition test(LOI) and, presto, the loss is exactly 13, 9 % as should be with theoretical clay formula.
I found out some of this information while working for Brisbane and Wunderlich (in my own time) and I have never disclosed my findings to anybody.
At my age now I would like you, my friends, to be the first ones to know THIS before I kick the bucket.
This means that the china clay (Greenbushes) was weathered in very short time due to hypogene forces (hot water vapor and chemical gases from within the earth at much higher temperature and pressure we use in a laboratory autoclave) and nowhere near 200-300 millions years. And now something practical. I wish we would use clays as a major ingredient in glazes and not just an agent to provide suspension and adherence. So please I would like some of you to calcine china clay or ball clay at about 800-1000° in the near future (about 1-2 Kg). We may use as much as 50-60% of clay in our experimental glazes.

Cheerio for now Mike