Linda Arbuckle on tue 2 jul 96
In response to:
From: Ed Brownlee
Subject: ed 1200maj report
I've been away to Penland School, where I met some great potters and saw
pottery friends, so I missed the beginning of this... but in comment to your
recent posting on tests...
Tin oxide added to your glaze in amounts of 5% or less will make the glaze a
"fattier" white. The zirconium opacifiers tend to be a bit more translucent.
I use both, as all tin will provoke tendancy to crawl where thick, and
you'll get chrome-tin pinking of the white glaze if you use decorating
colors with chrome. 5% tin seems to be the pivotal point for chrome-tin
pinking.
Adding clay to the decorating colors probably decreases the brush-ability.
I'd ditch the clay. If the colors are running, add less gerstley, or try
using neph sy, which is a higher range flux. Copper, cobalt, and iron won't
need a flux addition at all.
Keep us posted....
Linda
_______________________________________________
Linda Arbuckle E-mail: ARBUCK@nervm.nerdc.ufl.edu
Asst. Prof.
Univeristy of Florida
Department of Art 302 FAC
Gainesville, FL 32611 Ceramics: (352) 392-0228
Richard Burkett on tue 22 oct 96
I've been meaning to post this for a while but the recipe was at school and
I usually read my mail from home. Here's a cone 6 majolica recipe that one
of my students developed in the glaze class last semester. It has very
low amounts of boron (in the form of gerstley borate) so it better supports
a wide range of stain colors, even pinks, lavenders and other somewhat
fugitive colors. It should fit most clay bodies, but you may have to adjust
it to fit yours with out crazing or shivering.
Glaze name: Midrange Majolica 96
Cone: 4 - 5 - 6
Color: Opaque White
Testing: Tested
Surface texture: Shiny or Glossy
Firing: Ox. or Red.
Recipe: Percent Batch
Gerstley borate 4.85 242
Nepheline Sye. 30.09 1504
EPK 4.20 210
Dolomite 2.07 103
Whiting 8.49 424
Flint 41.09 2054
Zircopax 9.21 460
Totals: 100.00 % 5000 Gm
Also add:
Bentonite 3.00 150
Epsom salts 0.50 25
Comments:
From Linda Litteral - SDSU Glaze class 1996. She called it 'A-7
Chinese.' Tested for new Midrange majolica for class use. Almost boron
free - good for stain colors that are subject to dissolving in boron
glazes. Very stable, does not move during firing unless quite thick.
Will crawl slightly if very thick. Applies well either by dipping or
brushing. Works well with almost all Duncan EZ-Stroke underglaze
colors as majolica washes, as do Amaco velvet red versions of the
zirconium encapsulted red stains. Probably most stains would work well
also. Color possibities: Use mason stains mixed 50/50 with Pemco frit
P-25 or Ferro Frit 3124, or use 70 stain/30 gerstley borate in a
watery mix for colors over glaze or some combination of gerstley
borate and frit. Using too much gerstley borate may make the stain
change color or become pastel. Purple stains may need to have more
flux added up to 3 parts flux to 1 part stain. If you use all frit,
add liquid starch or CMC to colors for easier brushing and to minimize
smearing before they're fired. Use these Duncan EZ-stroke transparent
underglazes as overglaze wash for color: EZ003, EZ004, EZ007, EZ012,
EZ014, EZ019, EZ020, EZ021, EZ024, EZ025, EZ027, EZ028, EZ030, EZ032,
EZ161. Almost all the other EZstrokes will work, especially if thinned
slightly. The darker blues and the Sierra Yellow EZstrokes will
wrinkle and get rough if applied too thickly. CoverCoat CC 154 should
work as well. Most other CoverCoat colors will work when thinly
applied, but may be dry if thick. Try adding a teaspoonful of frit or
gerstley borate to a jar of CC underglaze for glossier color. Other
color possibilities include washes of the common colorants (mix chrome
and rutile 50/50 with gerstley borate or frit). A thin red iron or red
earthenware slip or possibly a red terra sigillata on the foot or
other exposed clay areas makes a nice contrast if used on a white clay
body. Other color possibilities: A nice dark blue green with: 2%
cobalt carb + 3% chrome oxide + 2% black iron oxide added to the
glaze.
Possible Health Hazards:
Flint: free silica-wear a NIOSH approved dust mask when handling dry
material
Unity Formula for Midrange Majolica 96:
0.074 K2O 0.426 Al2O3 5.347 SiO2
0.257 Na2O 0.099 B2O3 0.248 ZrO2
0.589 CaO 12.6:1 Si:Al Ratio
0.079 MgO
Percentage Analysis:
69.64 % SiO2
9.41 % Al2O3
1.50 % B2O3
1.52 % K2O
3.45 % Na2O
7.16 % CaO
0.69 % MgO
6.64 % ZrO2
Sue Davis on tue 22 oct 96
Richard, read your posting for Majolica glaze ^4-6 and am curious. I work in
Majolica but in the ^04 range with Mason stains as my coloring agent. How
does this base glaze compare to a ^04 range in glossy background, and can you
achieve the opaque, white color I need? I use a lot of tin in the base recipe
for my white. Also, do the EZ strokes give a nice, bright color like the
Mason stains? Am curious to try this on my stoneware. Also, how about crazing
and crawling? I do get pin holes in my glaze sometimes, will this firing
range eliminate this?
Thanks for any help, Sue Davis in sunny Florida
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