Category: Glaze > Purple
Created 2015-10-21 01:06:33 by Terry Rorison
Categories: Glaze > Purple
Firing Temperature: Δ6
Atmospheres: Oxidation
Surface Type: Matte - Semi
Transparency: Opaque

"I have introduced a cooling cycle to the firing. The cycle is as follows and the firing is accompanied by a Cone 6 witness cone. After 12 consecutive firings, the witness cones are identical from firing to firing."

The firing cycle:
Rate Temp Hold Time
rA1= 360 F1 = 900 0
rA2= 300 F2 = 1800 0
rA3 =200 F3 = 2016 0
rA4 = 108 F4 = 2197 0.3
rA5 = Full F5 =1800 0
rA6 =150 F6 = 1300 0
rA7 = 0000

To summarize, I fire at a rate of 360/hr to 900 degrees F, then at 300 degrees/ hr to 1800 degrees F, 200 degrees/hr until 2016 degrees F is reached, then 108 degrees/hour to 2197 at which time I hold it at that temperature for 30 minutes.

The kiln is shut off until a temperature of 1800 degrees F is reached and then turned on to slow the rate of cooling to 150 degrees/hr until 1300 degrees F is reached. At this point the kiln is turned off and cools naturally.

Western Pennsylvania Potters Community

Material Amount Batch Subtotal
Whiting 20
Nepheline Syenite (Theoretical) 18
Kentucky OM #4 Ball Clay 18
Frit 3134 14
Silica 3
Total Base:73
Tin Oxide 7.5
Red iron oxide 5
Cobalt Carbonate 1
Chrome Oxide 0.02
Total: 86.52

Percentage Analysis

Ingredient Amount SiO2 Al2O3 B2O3 MgO CaO K2O Na2O KNaO Fe2O3 TiO2 CoO Cr2O3 SnO2 LOI
Nepheline Syenite (Theoretical)1810.934.
Kentucky OM #4 Ball Clay189.945.
Frit 3134146.513.232.821.441.44
Tin Oxide7.57.5
Red iron oxide54.750.25
Cobalt Carbonate10.630.37
Chrome Oxide0.020.02
100% no LOI 40.6512.334.330.1219.031.354.365.716.650.290.840.0310.04

Unity Molecular Formula (UMF)



0.16 Na2O
0.03 K2O
0.79 CaO
0.01 MgO


0.28 Al2O3
0.15 B2O3


1.58 SiO2
0.16 SnO2
0.01 TiO2


0.1 Fe2O3
0.03 CoO





0.2 : 0.8

SiO2:Al2O3 Chart

Closest 58 neighbors in Glaze > Purple.

Click and drag to zoom
Stull Chart
SiO2:Al2O3 Ratio
SiO2:Al2O3 Ratio 5.59

Similar Base Recipes

No recipes with similar base ingredients and amounts were found.

Similar RO/R2O Unity Formulas

No recipes with similar RO/R2O Unity Formulas were found.

No reviews yet.


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
Whiting Harmful WARNING Causes eye irritation
Kentucky OM #4 Ball Clay Health Hazard WARNING May cause damage to lung through prolonged or repeated inhalation 2 0 0 E
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
Tin Oxide Harmful WARNING Harmful if swallowed.
Red iron oxide Health Hazard WARNING May cause damage to lung through prolonged or repeated exposure by inhalation
Cobalt Carbonate Health HazardEnvironmental Hazard DANGER May cause cancer
Suspected of causing genetic effects
May damage fertility or the unborn child
May cause allergy or breathing difficulties if inhaled
May cause a allergic skin reaction
Very toxic to aquatic life
Very toxic to aquatic life with long lasting effects
2 0 0 *
Chrome Oxide WARNING May be harmful if inhaled. May cause
irritation to eyes and respiratory tract. Slightly toxic if ingested.
2 0 1 E