White Low-Fire Glazes for Terracotta and Earthenware Clay

Best White Low Fire Glaze For Terracotta, Food-safe

White Low-Fire Glazes For Terracotta and Earthenware Clay

Receipts and practical testing at the end of this article

If you’re making your own white low-fire glaze for terracotta, chances are you are using some of these materials. I try to sum up the most commonly used, though it’s not a complete list:

Glass Formers:
Silica (Quartz)
Nepheline Syenite
Feldspar Soda (not a flux at low temperatures)

Traditional mineral fluxes:
Colemanite
Gerstley Borate
Lithium Carbonate (small amounts)
Potassium Feldspar
For foodsafe glazes, avoid soluble borates; use frits instead
Commercial Borax Frit / Boron Frits: Frit 3134 / 3124 / 3195 / 2962, etc.

Stabilizers:
Kaolin (China Clay)
Ball Clay
Bentonite
Alumina Hydrate
Calcined Kaolin

Whitening / Opacifying:
Common food-safe opacifiers:
Zirconium Silicate
Tin Oxide (expensive)
Historically used:
Bone Ash
Titanium Dioxide
Zinc Oxide (not an opacifier alone)

Other/Experimental:
Magnesium Carbonate (matte modifier)
Dolomite (satin/matte/ivory whites)
Strontium Carbonate (warmer / ivory)
Ilmenite (Used for rustic, speckled glaze surfaces)

A modern, safe glaze system can be:
Boron frit
Kaolin
Quarts
Zircon Opacifier

Base example:
50–70% Boron frit (e.g. 3124, 3195, 2962)
10–20% Kaolin
5–20% Quarts
5–15% Zirconium Silicate

Traditionally, white glazes for terracotta were made with Tin.
Today, Tin is both a rare and expensive metal.

Testing how durable your glaze is:

Lemon test: leave a lemon slice overnight
Vinegar soak: 24h; look for matte/dull areas
Dishwasher test: 10 cycles for wear
Spoon or knife test: See if the wide side of the spoon makes gray “lines” on the glaze, or if the knife easily makes scratches

White Low-Fire Glazes for Terracotta – Recipes

The goal for the next few months is finally get a grip on some nice white glazes, so please stay tuned.

Some testing:

white glaze 20 high alkali frit 5 feldspar 5 chalk 5 magnesium carbonate

Q02:
20 High alkali frit P2962.1
5 parts Feldspar Soda
5 Chalk
5 Magnesium Carbonate

It’s a start, absolutely interesting, I like how the glaze colors the terracotta without even covering it. The holes in the glaze are related to lumps in the glaze mix.

white glaze 20 borax frit 5 feldspar 5 chalk 001

white glaze 20 borax frit 5 feldspar 5 chalk 002

Q03
20 parts Borax frit P2953-01
5 parts Feldspar Soda
5 Chalk

It did not turn out white at all, but I like it: Glossy, frosty with bubbles

white glaze 20 high alkali frit 5 kaolin 5 kvarts 4 magnesium carbonate 002

white glaze 20 high alkali frit 5 kaolin 5 kvarts 4 magnesium carbonate 003

Q04
20 High alkali frit P2962.1
5 parts Kaolin
5 Quarts
4 Magnesium Carbonate

As thin it’s white with a good covering ability and a hard surface. I liked it even better as thick where it is a combination of transparent and glossy, and white “snowflakes” in it.

white glaze 20 borax frit 5 feldspar 5 talc 5 kaolin

Q01:
20% parts Borax frit P2953-01
5% parts Feldspar Soda
5% parts Talc
5% parts Kaolin

Not a finished glaze; yellow-white with cracks and pinholes, at thin it was quite ok.

White Low-Fire Glazes for Terracotta From Books:

From the book: Fired up with raku, by Irene Poulton.
Antique White (creamy white):

80% Gerstley Borate
20% Talc

From the book: Low-Fire Soda by Justin Rothshank.
Logan Wall’s Bills basic liner (white glossy):

65,8% Ferro Frit 3124
17,1% Kona F-4 Feldspar
6,5% Nephelin Syenite
10,8% Kaolin
Additives:
14% Zircopax
0,5% Rutile
2% Bentonite

From the book: AMAZING GLAZE by Gabriel Kline.
Chris Gustin White:

40% Frit 3124
30% Gersley Borate
25% Nepheline Syenite
5% Silica
8% Zircopax