[red porcelain coffee cup at 800x magnification]

Hi Nerd, yes seeing bubbles is pretty much all glazes.  see a thread started by Joel called Bubble Bubble Toil and Trouble if you haven't already.  I make a lot of comments about my own bubble research and observations there.  Yes, scale is critical - bubbles below a certain size are there, but cannot be seen by human eye.  It seems clear industry depends critically on this fact.  I may trot out some of these pictures again at some point if the bubble discussion re-emerges.  I think it ended up in a chemistry discussion really.  The righteous path on bubbles as I see it now is about particle sizes and relative amounts of fluxes vs very refractory materials in the glaze.

[vase with Srs glaze heavy reduction march 2015]

Thanks Nerd!

[crystal 1]

Sorry Nerd, still trying to get my avatar to work after it mysteriously disappeared a couple months ago. This was just a deliberately small resolution version to try ala Marcia Selsors recent suggestion - still does not work! Driving me nuts. Will try to find the larger format version and post, although not even sure if I remember where this shot came from. But as you will probably know it came from a digital microscope...

[Hakeme Vase]

Thanks guys!

[native material tests ready For bisque firing]

I would say go out and grab some, doesn't have to be much.  Clean any large chunks and debris out if it fires up strong and non-porous you have (probably) hit paydirt.  If not it can have a few possible alternate lives....