Glaze tests

Because I have created a contemporary shape for my tea pot and cup, to relate it back to when Insole Court was built by James Harvey Insole between (1790-1851) I decided to research into colours of that period. I found the book The anatomy of colour (Baty, P 2017) very useful, historian and paint expert Patrick Baty traces the evolution of pigments and paint colours together with colour systems and standards, and he examines their impact on the colour palettes used in interiors from the 1650s to the 1960s.

1800 colours1800 textures

These were the colour pallets which were most popular between the 1830-1900, I used these as a guide for search of glaze recipes, I decided to use The glaze book (Murfitt, S. 2002)

Recipes 

32 Antiques green glaze

Standard borax frit 80
Zinc oxide 10
Ball clay 10
Zirconium silicate 10%
Ilmenite 10%
Copper carbonate 5%

Antique green

I really like how this turned out, I love the effect of the mottled brown specks the ilmenite gives.

47 White opaque glaze 1100°

Calcium borate frit 40
Ball clay 20
Flint 40
Cobalt oxide 0.75%
Red iron oxide 2%

White opaque

I must have used a lot more Cobalt Oxide than I should have here but I love the textures!

50 Pale blue/pink/grey lava glaze

Standard borax frit 40
Calcium borax frit 20
Zinc oxide 20
China clay 5
Flint 5
Rutile 10
Silicon Carbide 1.5%
Copper oxide 1%

Pale blue pink lava

For this recipe I didn’t use Silicon carbide o’r copper oxide which turned it a mottled yellow colour, i don’t think i’ll use this colour as it’s got an uneven consistency.

51 Brown oil-like glaze

Standard borax frit 92
China clay 8
Red iron oxide 15%
Manganese dioxide 4%

Brown oil like

Very uneven consistency but it has a really nice shine, i think i used a good amount of Manganese dioxide to get a good matching brown.

14 Semi-opaque white stone glaze 1060°

Calcium borate frit 20
Standard borate frit 25
Whiting 20
China clay 15
Flint 20
Tin oxide 10%

Semi opaque white

27 Mottled dark turquoise glaze

Standard borax frit 75
Ball clay 15
Zirconium silicate 10
Copper carbonate 6%
Cobalt Oxide 3%

Mottled dark turquoise

Standard borax frit: Good general purpose Leadless frit with a medium thermal expansion, which is ideal as the major ingredient in Earthenware glazes.
Zinc Oxide: Readily dissolves and acts as a flux.
Ball clay: Fine particled clay that is universally used in glazes for suspension.
Zirconium silicate: Serves as an opacifier
Ilmenite: Produce dark brown specks
Copper carbonate: Produce shades of green or turquoise (Red in a reduction firing)  
Calcium borate frit:
Substitute for Gerstley Borate or Colemanite in special effect glazes recipes and also as a constituent in Matt earthenware glazes.
Flint: Optimises the surface hardness of un-fired glazes, to stabilise viscosity, and to enhance glaze suspension. 
Cobalt oxide:  
It is a very strong oxide, and using very small quantities yields bright, intense blues. Because cobalt oxide is not as finely powdered as cobalt carbonate, cobalt oxide is more likely to create blue specks.
Red iron oxide: During firing all irons normally decompose and produce similar colours in glazes and clay bodies. It is an important source for tan, red-brown, and brown colours in glazes and bodies.
Rutile:
Produces many crystalline, speckling, streaking, and mottling effects in glazes during cooling in the kiln and has been used in all types of coloured glazes to enhance the surface character.
Silicon Carbide:
 The silicon part takes up available oxygen to make SiO2 and the carbon combines with oxygen to make the CO2 that creates the blisters and bubbles. Using this mechanism it is possible to create reduction effects in oxidation firings.
Copper oxide: 
The oxide form of copper can give a speckled colour in glazes whereas the carbonate form will give a more uniform effect.
Manganese dioxide:
Behaves in a refractory manner, stiffening the melt. Manganese browns have a different, often more pleasant character than iron browns.
Whiting:
Composed essentially of pure Calcium Carbonate. It is a high temperature flux which gives durability and hardness to glazes.
Tin oxide: 
Tin oxide is used to make the glaze a transparent opaque


Photo 15-05-2018, 10 19 22

I have been able to match the glazes quite well, I really like how you can see the Ilmenite come out in the antique green glaze, this will be the main colour I will use for my tea set, I also really like the textures in the white opaque glaze which has turned blue, I must have used a lot more Cobalt oxide than I should have.

All of these glazes were fired at the temperature of 1100 °, this was my firing schedule.

10:00 10%
11:00 20% 84 °
12:00 40% 175 °
1:00 50% 331 °
2:00 70% 510 °
3:00 85% 768 °
4:00 85 % 958 °
4:30 85% 1115 ° (cone fallen)

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Murfitt, S. (2002). The glaze book. London: Thames & Hudson.

Baty, P. (2017). The anatomy of color. Thames and Hudson Ltd.

 

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