Category: Glaze > Blue
Created 2017-09-12 02:05:26 by mitch henke
Categories: Glaze > Blue
Firing Temperature: Δ5-6
Atmospheres: Oxidation
Surface Type: Glossy

I am firing this at C5 on a variety of clays.

Original information below:
Source/Alternate names: James Chappell The Potters Complete Book of Clay and Glazes

Source/Alternate names: same oxides as Slate Blue With Green Specks, similar to Blue Jean Blue and Cobbled Floating Blue

Notes: Candice Roeder: a deep blue-brown background of great depth with lighter mottled blues that seem to float on the surface of the background glaze. with more of the lighter mottled blues where the application is thickest. Watch thickness near the bottom of the pot. It fires best on the light side of cone 6 (standard cone just bending), seems to get greener and more fluid the higher you go. Cone 5 works well, too. The book says to weigh the ingredients very carefully, use distilled water or water that is known to have a low mineral content. Mix then add the CMC solution. The book warns that the glaze is fickle, and recommends against firing this glaze in the same kiln with glazes that contain copper, chrome, nickel or manganese. Mineral content of the water is an important factor. I have noticed an adverse effect as the author noted, and now fire an entire kiln load of this glaze.

Notes: Martha Muzychka: not what I expected, mostly green with a few spots of blue. On black stoneware clay, it gives an unusual cloudy effect.

Notes: Ivy Glasgow: a popular and beautiful (when done right) glaze. The original Floating Blue pigments have been tested and found to be food safe. When floating blue works, it is lovely. Key seems to be firing to no more than Cone 5-1/2 and cooling quickly.

Notes: James Chappell: the colours seem to float on a surface of a darker background of great depth, reminiscent of a deep pool of water. Its colour and opacity vary greatly with thickness so it highlights irregularities in the surface. Phase separation in the translucent matrix makes the colour swirl as small rivulets of more fluid glass flow around more viscous phases. Titanium crystals in the matrix make it sparkle. Calcium-borate boron-blue crystals grow on the surface. Bubbles of escaping gases create pools of lighter coloured glass surrounded by darker rings. Small black speckles are produced by unground particles of iron. Use distilled or low mineral water, force all material through an 80 mesh screen, stir thoroughly before and during use to prevent settling out of the iron content, apply the thickness of a dime, fire to cone 6 oxidation exactly, and cool normally. Do not substitute any other chemicals for those given, it is a fickle glaze. It depends on the Gerstley borate to suspend it.

Notes: I substitute Cobalt Carb 2.0. What caught my eye, was the description of it as slate blue, which doesn't fit my results. So, I picked up the original recipe, and it differs from the one Sharon posted. You might try this version in your tests. It is called Floating Blue...from James Chappell's book, Clay and Glazes. This glaze produces a deep blue-brown background of great depth with lighter mottled blues that seem to float on the surface of the
background glaze. The glaze has more of the lighter mottled blues where the application is thickest. Watch thickness near the bottom of
the pot. The C.M.C. measurement refers to a premixed CMC and water solution. For the Silica, I use 325 mesh Flint. The rutile, is just powdered rutile from the ceramics supply. It fires best on the light side of cone 6 (standard cone just bending), seems to get greener and more fluid the higher you go. Cone 5 works well, too. I do not find a need for bentonite. The book says to weigh the ingredients very carefully, use distilled water or water that is known to have a low mineral content. Mix then add the CMC solution. Sieve two or three times through a 60 to 80 mesh sieve to thoroughly disperse the cobalt, iron, and rutile. The book warns that the glaze is fickle, and recommends against firing this glaze in the same kiln with glazes that contain copper, chrome, nickel or manganese. Mineral content of the water is an important factor. I have noticed an adverse effect as the author noted, and now fire an entire kiln load of this glaze. The glaze should be stirred occasionally during application because the iron has a tendency to settle.

Chappell's Suggested variations:
Stipple on additional glaze with brush or apply with sponge for an even more mottled effect. Or: lightly sponge a thin wash of 3 grams of chrome oxide to 100 grams of water plus a tablespoon of CMC over the top to produce a floating blue glaze with subtle green tints. Or: Over the glaze, sponge lightly with a rutile wash consisting of 2 grams rutile per 100g of water for a floating blue glaze with slightly tan crystalline tints on the surface. submitted by: Candice Roeder source for original recipe: James Chappell

Material Amount Batch Subtotal
Nepheline Syenite (Theoretical) 47.3
Gerstley Borate 27
Silica 20.3
EPK 5.4
Total Base:100
Rutile 4
Red iron oxide 2
Bentonite 2
Cobalt Oxide 1
Total: 109

Percentage Analysis

Ingredient Amount SiO2 Al2O3 B2O3 MgO CaO K2O Na2O KNaO P2O5 Fe2O3 TiO2 CoO LOI
Nepheline Syenite (Theoretical)47.328.7111.020.050.332.184.646.820.050.33
Gerstley Borate2740.277.240.945.240.111.081.190.030.110.037.97
Silica20.320.3
EPK5.42.472.020.010.010.020.020.010.040.020.8
Rutile40.43.6
Red iron oxide21.90.1
Bentonite21.190.40.040.020.020.060.080.070.2
Cobalt Oxide10.930.07
Total10956.6613.717.241.045.62.325.788.10.042.563.650.939.47
100% no LOI 56.9313.787.271.045.622.335.818.140.042.573.660.94

Unity Molecular Formula (UMF)

FLUXES

RO/R2O

0.38 Na2O
0.1 K2O
0.41 CaO
0.11 MgO
STABILIZERS

R2O3

0.55 Al2O3
0.43 B2O3
GLASS-FORMERS

RO2

3.87 SiO2
0.19 TiO2
OTHER

 

0.07 Fe2O3
0.05 CoO
SILICA:ALUMINA

SiO2:Al2O3

7.01

FLUX RATIO

R2O:RO

0.48 : 0.52

SiO2:Al2O3 Chart

Closest 100 neighbors in Glaze > Blue.

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Stull Chart
SiO2:Al2O3 Ratio
SiO2:Al2O3 Ratio 7.01

Similar RO/R2O Unity Formulas

R2O3 - STABILIZERS RO2 - GLASS FORMERS RO/R2O - FLUXES
Recipe Name ΔTemp Al2O3 B2O3 SiO2 ZrO2 SnO2 TiO2 KNaO K2O Na2O CaO MgO ZnO BaO PbO Li2O SrO
Chappell Floating Blue, Blue Hare (variation) 5-6 0.55 0.43 3.87 0.19 0.48 0.1 0.38 0.41 0.11
Speckly 0.54 0.43 3.83 0.19 0.48 0.1 0.38 0.41 0.1
Floating Blue 6 0.54 0.43 3.83 0.19 0.48 0.1 0.38 0.41 0.1
Chappell Floating Blue, Blue Hare 6 0.55 0.43 3.87 0.19 0.48 0.1 0.38 0.41 0.11
Slate Blue With Green Specks 6 0.56 0.43 3.89 0.19 0.48 0.1 0.38 0.41 0.11

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Hazards

09/2016 Note: This is a new feature. If a recipe material is not listed, 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
Material Pictograms Signal Word Hazard Statements Health Flammability Hazard Protection
Gerstley Borate
Silica HarmfulHealth Hazard DANGER From 200-Mesh SDS:
May cause cancer by inhalation.
Causes damage to lungs through prolonged or repeated exposure by inhalation.
* 0 0 E
EPK HarmfulHealth Hazard DANGER EPK Kaolin is a naturally occurring mineral, which may contain amounts of crystalline silica
typically 0.1-1.0%, may cause damage to respiratory system through prolonged or repeated
exposure.
1 0 0 E
Rutile 1 0 0
Red iron oxide Health Hazard WARNING May cause damage to lung through prolonged or repeated exposure by inhalation
Bentonite Harmful WARNING Causes eye irritation
Causes skin irritation
May cause respiratory irritation
Cobalt Oxide HarmfulHealth Hazard WARNING Suspected of causing cancer
Harmful if swallowed
May cause allergy or breathing difficulties if inhaled
May cause an allergic skin reaction
2 0 0 *