Category: Glaze > Specialty > Crackle
Created 2017-08-06 09:12:25 by kenneth ibbett
Categories: Glaze > Specialty > Crackle
Firing Temperature: Δ6-8
Atmospheres: Oxidation
Surface Type: Glossy - Semi
Transparency: Translucent

This was fired at 1250 with a 10 minute soak and cone 9 was bending.pale ivory and crackle when not recommended for functional ware. Be sure to glaze both sides as uneven pressure may cause dunting.
Bone ash may cause flocculation and the raw glaze will crack off so deflocculate! Apply as thick necessary SG 1.5+. Additions of color > 1% will stop crackle formation.

Material Amount Batch Subtotal
Nepheline Syenite (Theoretical) 71.59
Talc (Theoretical) 14.31
EPK 9.55
Bone Ash 2.86
Red iron oxide 0.95
Epsom salts 0.74
Total: 100

Percentage Analysis

Ingredient Amount SiO2 Al2O3 MgO CaO K2O Na2O KNaO P2O5 Fe2O3 TiO2 LOI
Nepheline Syenite (Theoretical)71.5943.4616.680.
Talc (Theoretical)14.319.074.560.68
Bone Ash2.861.61.210.05
Red iron oxide0.950.90.05
Epsom salts0.740.120.62
100% no LOI 58.8420.944.932.193.447.2610.

Unity Molecular Formula (UMF)



0.37 Na2O
0.12 K2O
0.12 CaO
0.39 MgO


0.65 Al2O3


3.11 SiO2


0.02 Fe2O3
0.03 P2O5





0.49 : 0.51

SiO2:Al2O3 Chart

Closest 12 neighbors in Glaze > Specialty > Crackle.

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Stull Chart
SiO2:Al2O3 Ratio
SiO2:Al2O3 Ratio 4.77

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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
Talc (Theoretical) Harmful WARNING Causes mild skin irritation
Harmful if inhaled
May cause respiratory irritation
1 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
1 0 0 E
Bone Ash
Red iron oxide Health Hazard WARNING May cause damage to lung through prolonged or repeated exposure by inhalation
Epsom salts