Created by Glazy Admin 2015-07-16 06:59:40, updated 2015-09-25 00:18:21

Theoretical Material

Type: Flux

Weight: 140.6000
Formula Weight: 140.5683
LOI: 29.5000
Thermal Expansion: 0.0000
Oxide SiO2 Al2O3 B2O3 MgO CaO K2O Na2O P2O5 Fe2O3 TiO2
% Analysis 14.80 1.00 26.80 3.50 19.40 0.40 4.00 0.10 0.40 0.10
Formula 0.491 0.020 0.768 0.173 0.690 0.009 0.129 0.001 0.005 0.003

Gerstley borate supplies B2O3, CaO, other fluxes, SiO2, and Al2O3. Gerstley borate is a calcium borate ore containing the mineral Ulexite ( 3CaO Na2O 5B2O3 16H2O ), along with accessory minerals such as Bentonite, Colemanite, and Probertite. Gerstley borate was formed in marshes and drying lake basins during the Miocene (10 million years ago).
Gerstley borate is named after James Gerstley, former managing director of Borax Consolidated Ltd. It is manufactured by U.S. Borax and Chemical Corp.; the mine is located near Death Valley, CA.
G.B. is an inexpensive source of B2O3 and CaO in glazes. It is often used in place of colemanite. The primary differences are:
1) colemanite contains a higher concentration of B2O3,
2) G.B. contains Na2O, which may affect the color and surface of some glazes, and
3) the Bentonite component of G.B. - up to 18% - significantly affects the properties of the raw glaze. (Some other sources indicate that this is not bentonite, but rather shale. GB glazes do tend to gel in either case.)

Other points from IMC:
1) GB is slightly soluble and tends to gel the glaze, necessitating excessive water and resulting in greater shrinkage of the raw glaze, which leads to crawling and other problems, especially when there is also a lot of clay in the glaze. Epsom salts (4g per 100g GB) can help. 2) The chemical and physical properties of the material (composition, mesh size, etc.) change over time. 3) GB can contain gypsum and lead to lime popping.
Analyses:
Axner: (web site, 2001)
% 4.5 Na2O 0.25 K2O 3.5 MgO 22.0 CaO 1.0 Al2O3 29 B2O3 0.2 Fe2O3 10.0 SiO2 29.0 LOI
Obstler: (Hammill & Gillespie)(also includes 6.2 LOD whatever that is)
% 3.6-5.3 Na2O 2.9 MgO 17.1-20.6 CaO 1.3 Al2O3 25-28.9 B2O3 0.35 Fe2O3 10.6 SO2 30.5 LOI
Hopper:
2 CaO Na2O 3 B2O3 7 H2O
Cushing:
CaO B2O3 5 H2O
IMC:
% 9.31 Na2O 16.85 CaO 52.25 B2O3 21.59 LOI
ClayArt from Axner:
This product is composed of a mixture of the minerals Colemanite and Ulexite. This material contains approximately 28.0% Boric Oxide (B2O3), 5.3% Sodium Oxide (Na2O), 20.6 Calcium oxide (CaO) and 25% water of crystallization.

Hazards

09/2016 Note: This is a new feature. If there is no safety information below, then that material's data has not yet been added. Some materials only have GHS ratings, while others only have HMIS ratings. Warnings differ between systems and countries. Glazy does not take any responsibility for accuracy of linked SDS information. Contact your ceramics supplier for safety information for your specific materials.
Globally Harmonized System (GHS) Hazardous Materials Identification System (HMIS) SDS Link
Pictograms Signal Word Hazard Statements Health Flammability Hazard Protection

Recipes using this material

Name Amount of Gerstley Borate Temp. Atmospheres Surface Transparency Si:Al R20:RO Author
rutile ash 28 Δ5 - 10 Oxidation
Reduction
Salt & Soda
Semi-matte 27.36 0.3 : 0.7 timothy graham
Gold Beryl 21 Δ6 Oxidation
Neutral
Glossy Transparent 10.51 0.14 : 0.86 Naomi Duffey
Emerald 21 Δ6 Oxidation
Neutral
Glossy Transparent 10.51 0.14 : 0.86 Naomi Duffey
Ruby (C.M. Sept. '17, p. 65) 21 Δ6 Oxidation
Neutral
Glossy Translucent 10.51 0.14 : 0.86 Naomi Duffey
Reynold's Rap 63 Δ08 - 04 Raku
12.81 0.17 : 0.83 Ceramic Recipes
Roy Clear 1 20 Δ6 Semi-glossy 7.97 0.16 : 0.84 Glazy Admin
Unzicker Brothers Tenmoku 12.5 Δ9 - 12 Reduction
Salt & Soda
Wood
Semi-glossy 6.48 0.52 : 0.48 Nate Willever
VC 611 12 Δ6 Oxidation
Glossy Transparent 5.23 0.51 : 0.49 Ginger Lukas
Purple Haze 6.9 Δ10 Reduction
Satin Opaque 10.14 0.25 : 0.75 Glazy Admin
Sue's Lavender -new (Cedar Hill) 640 Δ6 Oxidation
Glossy Opaque 6.88 0.32 : 0.68 Sue McLeod
Lavender - old - partial recipe (Cedar Hill) 33.51 Δ6 Oxidation
Glossy Opaque 22.16 0.3 : 0.7 Sue McLeod
Lavender - old - full recipe (Cedar Hill) 21 Δ6 Oxidation
Glossy Opaque 14.14 0.14 : 0.86 Sue McLeod
Sue's SJC -new (Cedar Hill) 4 Δ6 Oxidation
Reduction
Glossy Semi-opaque 8.59 0.5 : 0.5 Sue McLeod
SJC -old (Cedar Hill) 5.1 Δ6 Oxidation
Reduction
Glossy Translucent 8.95 0.6 : 0.4 Sue McLeod
Sue's Woo Yellow -new (Cedar Hill) 9 Δ6 Oxidation
Reduction
Matte Opaque 5.12 0.3 : 0.7 Sue McLeod
Sue's Eggshell (Cedar Hill) 12 Δ6 Oxidation
Semi-matte Opaque 4.97 0.39 : 0.61 Sue McLeod
Randy's Red (Cedar Hill) 30.6 Δ6 Oxidation
Glossy 15.88 0.17 : 0.83 Sue McLeod
Orange Brown (Cedar Hill) 7.92 Δ6 Oxidation
Semi-matte Opaque 8.74 0.2 : 0.8 Sue McLeod
Eggplant (Cedar Hill) 12.77 Δ6 Oxidation
Matte Opaque 9.34 0.23 : 0.77 Sue McLeod
VC Matte White 10 Δ5 - 7 Oxidation
Satin-matte Opaque 5.72 0.61 : 0.39 Roxi Clark
Floating Blue 27 Δ5 - 6 Oxidation
Semi-glossy Semi-opaque 7.01 0.47 : 0.53 mitch henke
Matt's Iron Red 15 Δ6 Oxidation
Semi-glossy Semi-opaque 9.44 0.2 : 0.8 Matt Garrett
Matt's Shino 18.5 Δ6 Oxidation
Semi-glossy Opaque 8.63 0.42 : 0.58 Matt Garrett
Red Green 15 Δ6 Oxidation
Transparent 4.24 0.52 : 0.48 Ceramic Recipes
SL Temmoku 15 Δ5 - 7 Oxidation
Neutral
Reduction
Glossy Semi-opaque 8.14 0.35 : 0.65 Tamas Ferencz
Clear bob's base 9.1 Δ7 - 8 Oxidation
Reduction
Glossy Transparent 8.2 0.13 : 0.87 Glazy Admin
Cream breaking brown WWW 264 22 Δ6 Oxidation
Glossy 12.03 0.3 : 0.7 Daniel Spruyt
Sunny Yellow 23 Δ5½ - 6 Oxidation
Satin Opaque 4.55 0.35 : 0.65 Lisa Cotterman
Antique White 25 Δ6 Oxidation
6.38 0.35 : 0.65 Jake Bish
Jen's Juicy Fruit Variation Base (variation) 9 Δ6 Oxidation
Semi-matte Translucent 5.3 0.66 : 0.34 mitch henke
Orange Street 17.9 Δ6 Oxidation
9.22 0.18 : 0.82 mitch henke
Rainbow Sand 71 Δ010 - 04 Raku
Matte Opaque 9.65 0.16 : 0.84 Sid Henderson
Egyptian Blue Raku 65 Δ08 - 05 Raku
Glossy Translucent 7.37 0.23 : 0.77 Sid Henderson
Chappell Floating Blue, Blue Hare (variation) 27 Δ5 - 6 Oxidation
Glossy 7.01 0.48 : 0.52 mitch henke
Folk Art Guild White 18 Δ5 - 6 Oxidation
Semi-glossy Opaque 6.07 0.2 : 0.8 Mary Higgins
Glossy Dark Blue 12 Δ6 - 8 Oxidation
Glossy Transparent 7.05 0.25 : 0.75 kenneth ibbett
Wood's Transparent Ice Blue -- Cone 04 26 Δ05 - 04 Oxidation
Glossy Transparent 7.11 0.44 : 0.56 Clemson University---Ceramic Dept.
Lisa Orr's Base Cone--04 Glaze 9   Oxidation
14.8 0.75 : 0.25 Clemson University---Ceramic Dept.
Lisa Orr's Turquoise Cone--04 Glaze 9 Δ05 - 04 Oxidation
14.8 0.75 : 0.25 Clemson University---Ceramic Dept.
Lisa Orr's Molasses Cone--04 Glaze 9 Δ05 - 04 Oxidation
13.38 0.75 : 0.25 Clemson University---Ceramic Dept.