New bowls with old problems

Tom,
If you take a click back from the Stull map, there's some other good links here:
www.mattanddavesclays.com/Science/ScienceHome.html
That glaze calc link is a few years out of date and may not match current material chemistry?
I'm starting to test clays as well....

Arnie,
I think that glaze calc class is worth every penny of interest that I owe the US dept. of education.

Hi Greg -
I've had the same experience - sometimes lots of crystals with thicker glazes - and I also looked over my pieces with the biggest individual crystals, and they are often on pieces with the thickest application of glaze - SO, that's why, whenever I post any results, I'm writing 'this is what I got' and in my mind I'm saying 'most of the time'.

Looking over your 3 bowls - 2 and 3 give me trouble because I keep inverting them in my mind - like I'm looking at the bottom of a piece, with a foot, and not from the top down, so I keep bending it in the other direction. Are the rims almost flat or sloping up or down? On the first piece, if the rim and first circle of brown/gold glaze are relatively flat and then there's a slope where the glaze runs off and into the center where it's thicker - I'd put both less glaze and less zinc - let the slope be almost clear of crystals - like in #2 but larger. Why is the ground bluish in #1? An engobe? I THINK I'd try without it - I'd probably reduce the zinc by 2 gms to start or down to 22 gms, at most - all of my pieces have between 20 and 22 gms of glaze and a half a gm makes a difference - but, going back to paragraph 1, not every time.

For a refire, I'd put a glaze with no more than 12 gms of zinc - probably come out with multitudes of tiny crystals - but my ability to predict is not very reliable.

I think you've got a great concept going -

Arnie

Hi Greg -

You may be right - 12 gms Zn could be too little - but since you're applying more glaze on a bowl and don't want to make it too too thick, the new glaze has to have much less Zn in order to make an impact on the total glaze.
Thanks for the profile pics - the bottoms look close to flat(?) - then likely the crystals in the center will look different than those on the slope - and the glaze from the slope will pile up around the flat center. The pieces I have pictured on previous pages have a slope to the center, so the crystals don't have the junction between flat and slope. So you want to put more on the top of the slope and less on the bottom of the slope and then treat the center like it's a plate, with glaze that won't move. Easier said than done, as you know!
What did the first bowl look like unreduced? I assume the glaze is 'gold stuff'. I like them both - reduced and unreduced. Difference in the reflected light in the pictures - I like the lighter tones of the gray from the angle in the oblique shot.

Arnie

HI Greg - yeah, I had an uneasy feeling when I was typing it - like, where did that come from? But so many plates and bowls look really nice when viewed at an angle where the light is reflecting 'obliquely', and not straight back at the viewer.

From google search - synonyms for 'oblique' -

synonyms: slanting, slanted, sloping, at an angle, angled, diagonal, aslant, slant, slantwise, skew, askew, cater-cornered, kitty-corner
"an oblique line"

Arnie