Category: Glaze > Specialty > Crawling
Created 2017-10-08 17:41:44 by Sid Henderson
Categories: Glaze > Specialty > Crawling
Firing Temperature: Δ9-10
Atmospheres: Oxidation, Neutral, Reduction
Surface Type: Satin - Matte
Transparency: Opaque

This is a magnesium crawl glaze that contains a lot of clay. This means it can be applied on top of some other glazes and still retain its reticulations.

I invented this glaze myself. My goal was to make a crawling glaze that could be applied thick and not flake off.

Mix this glaze up thick- preferably in small batches and to the consistency of yogurt.

Apply a thin layer of a dark glaze, high in clay such as satin black to leather-hard ware or green ware, or barnard slip, and bisque this lower layer onto the clay. Dark clays also work well.

Apply a couple coats of Sonoran Crawler on top of the bisqueware with a brush and cease application once you observe cracking. The glaze will crack in the direction of your brush strokes! The more times you brush over the glaze as it dries, the better it adheres.

Under heavy reduction or on top of certain iron bearing bodies it can flash.

You can try adding a pinch of soda ash to the glaze in order to make it a little less thick without lowering the water content. Thinning this glaze down with water WILL cause it to peel off the piece, keep that specific gravity REALLY high. One day I may try mixing it to a thick paste and applying with a palette knife, but for now, yogurt consistency with a calligraphy bamboo brush works for me.

Test this glaze on top of various glazes. I've not had great luck with it over Temmoku, the fine powdery temmoku glaze prevents it from adhering properly. Shinos on the other hand seem to work well underneath it, and the soda ash from the shinos changes the texture in interesting ways.

To adjust the texture, change the ratio of Talc and Spodumene:
Decreasing talc, increasing spodumene by 2% results in a smoother, more lumpy surface.
Decreasing spodumene and increasing talc by 2% results in a rougher, more papery-bark-like surface.

Of course, test adjustments before using. Can you tell I have a bit of an obsession?

Material Amount Batch Subtotal
Lincoln Fire Clay 27
Magnesium carbonate 25
Talc (Theoretical) 20
Spodumene (Theoretical) 18
Zircopax 10
Total Base:100
Soda Ash 0
Total: 100

Percentage Analysis

Ingredient Amount SiO2 Al2O3 MgO CaO Li2O K2O Na2O KNaO Fe2O3 ZrO2 LOI
Lincoln Fire Clay2714.
Magnesium carbonate2511.9513.05
Talc (Theoretical)2012.686.370.95
Spodumene (Theoretical)1811.634.931.44
Soda Ash0
100% no LOI 50.2116.5522.280.071.740.240.10.340.728.1

Unity Molecular Formula (UMF)



0.09 Li2O
0.9 MgO


0.26 Al2O3


1.36 SiO2
0.11 ZrO2


0.01 Fe2O3





0.1 : 0.9

SiO2:Al2O3 Chart

Closest 22 neighbors in Glaze > Specialty > Crawling.

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Stull Chart
SiO2:Al2O3 Ratio
SiO2:Al2O3 Ratio 5.15

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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
Lincoln Fire Clay
Magnesium carbonate WARNING Causes mild skin irritation
Causes eye irritation
Talc (Theoretical) Harmful WARNING Causes mild skin irritation
Harmful if inhaled
May cause respiratory irritation
1 0 0 E
Spodumene (Theoretical) Health Hazard DANGER May cause cancer by inhalation.
Causes damage to organs through prolonged or repeated exposure.
Soda Ash Harmful WARNING Causes skin irritation.
Causes serious eye irritation.
2 0 0 B