Monday, 19 February 2018

Earthenware tests 18/2

Out of the kiln this morning a number of Earthenware cone 04 glaze tests.
I'm still just trying to find successful base glazes, retesting some of the recipes I've tried before to make a base line for revisions.

All were fired to 1080 degrees Celcius on Keanes Earthenware tiles bisque fired to cone 04.

Worthington Clear 
EW cone 04

Gerstley borate     55%
Eckalite                30
Silica                    15

Very clear glaze, some bubbles in suspension in thickest parts.

Glaze tests 18/2

cone 04

Frit 3124               50
Eckalite                15.65
Whiting                16.65
Silica                    17.75
Total                            5

Nice smooth matte glaze

Glaze tests 18/2

clear EW, cone 04

Frit 4131              83.3
Eckalite               16.6
* batches 2 and 3 combined and whizzed up to be smoother

This seems quite matte even though its a clear recipe. Much better results from first try when I must have put incorrect amounts in. Whizzed up. Need to buy a sieve.

Glaze tests 18/2

Julie's Satin
cone 04

Whiting                   17
Gerstley borate        27
Lithium carbonate     6
Nepheline syenite      4
Eckalite                    12
Silica                        34

This glaze is still cracking. Which is a pity because I like the quality of its matte surface.
Will maybe try to modify it though I have tried before with no improvement.

Glaze tests 18/2/18

Satin Base SB

This is the old batch remixed. The white version of this has a tendency to late crazing which is a pity because I really like the creamy surface of this.

Glaze tests 18/2/18

Earthenware tests 10/2/18

AB Clear glaze Frit Eckalite LB revised to use Strontium carbonate LB revised to use Whiting


Wednesday, 14 February 2018

Five Earthenware Base Recipes

Originally written 26 Sept 2016
glaze testing

Testing of five different Cone 04 matte or satin base recipes. All of the recipes have very similar ingredients, but different ratios.

These tests weren't ultimately successful as a week later four of them had crazed.

Retesting Julie's Satin (JMBC) and also testing a variation (JMBC revA), revised using hints from Glaze Simulator.

 A. Jackie's Matte via Priscilla Hollingsworth

38  Gerstley borate
10    Lithium carbonate
5    Nepheline syenite
5  Eckalite 2
42  Silica

5% Zircosil

Glaze testing

B. Satin Base (from here)

65.5 Ferro frit (4124) 3124
11    Nepheline syenite
5      Eckalite
42    Silica

C. Julie's Satin (from here)

27  Gerstley borate
7    Lithium carbonate
17  Whiting
4    Nepheline syenite
11  Eckalite 2
34  Silica

 D. Hirsh's Satin Matte

32  Gerstley borate
9    Lithium carbonate
17  Whiting
4    Nepheline Syenite
4    Eckalite 2
35  Silica

2% Bentonite

 E. Julie's Matte revised to fix crazing (JM rev A)

27  Gerstley borate
6    Lithium carbonate
17  Whiting
4    Nepheline syenite
12  Eckalite 2
34  Silica

Monday, 26 September 2016

Currie Grid

Glaze testing

Learning to do a stoneware test grid using Ian Currie's method for testing fluxes, alumina and silica ratios.

This is a Cone 6 Base Glaze.
Calculation page here.

Work out the flux ratios you want to use and then add them at the top. Click calculate and you have your formula. The Horizontal scale moves from C in the bottom left corner right towards high silica and upwards on the vertical plane towards high alumina.

Fluxes used are Frit 4124, Potash feldspar and Whiting.

Lucy Burley's Matte

Glaze testing

 I found this recipe on Ceramic Arts Daily's article about Green, Blue and Turquoise glazes. I love these colours and I'm looking for matte glazes for cone 04 firings.

 I have substituted Strontium carbonate for Barium carbonate.

I did a rough line blend, rough because I started the test using a teaspoon to measure units in the blend and ran out of glaze mix.

Lucy Burley's Matte Glaze Recipe

10    Strontium carbonate
45    Frit 3134
15    Potash Feldspar
15    Ball Clay FX
15    Eckalite 2


I love the colours in these tests. You can't see in the photo but this glaze bubbled at the edges.

I think this is because I didn't add enough water to the glaze mix and it went on very thick.

It isn't very matte either, a little shiny for a matte glaze. I might try to tweak it if I make it again to tone down the shininess and fix the bubbling.

Saturday, 17 September 2016

Julie's Satin Triaxial - Blog Ceramique

Glaze testingGlaze testing

This glaze test is for another Blog Céramique triaxial - Julie's Satin Base in green/blue

It's based on a cone 04 satin/matte base glaze recipe, which I think is based on the popular Jackie's Base glaze found around the net - the ingredients are similar - but this has added Calcium Carbonate (as an opacifier?) and different ratios. I used it on Keane's Earthenware 37 fired in my home kiln, an old Ward.

I mixed this one at home and fired it with a mixed firing of bisque and glazed pieces. One of the benefits of firing to cone 04 is being able to mix loads.

I had problems with reaching temperature as I had the controller programmed wrong and the kiln turned off too early before the cone had bent. Took another hour of fiddling with the controller to get it melted.

I don't think I did slow cool on this firing but it sort of had a soak due to the mistake.

The only substitution is Eckalite 2 for EPK which is unavailable here.

While I had the base mixed I did some extra experiments with cobalt, light blue stain and rutile.

Julie's Satin Base

17    Calcium carbonate
27    Gerstley borate
7      Lithium carbonate
4      Nepheline syenite
11    Eckalite 2 (my substitute for EPK)
34    Silica

In the Triaxial
A was the base glaze,
B was 3.5% Copper carbonate
C was 1% Chrome Oxide


I think I might have made the colour too strong too, I can't remember if I divided the amounts into thirds or just put the whole amount in each corner.

As it is the chrome seems unmelted and has taken on a rough burnt looking texture where it is most concentrated. The colours certainly look different to the sample tests on the BC blog.

Also the glaze has crazed in its base form and on some of the copper side.

I love the finish of this one though and will try to reformulate it to fix the crazing. Has a lovely thick buttery matte texture.

Naragon White cone 6 results

Glaze testGlaze tilesGlaze testing

Naragon White version 1

31%    Soda Feldspar

2      Bentonite

Mixed dry and then water added. Divided into three pots of 66.6ml each.

The triaxial with three corners as follows starting from the apex:

A 10%  Tin Oxide  (100 x 10 x 33.3/100) added 3.33g

B 7%    Copper Carbonate (100 x 7 x 33.3/100) added 2.33g
C 2%    Cobalt Carbonate, 10%  (100 x 10 x 33.3/100) added 0.66g
   10%   Rutile flour (100 x 10 x 33.3/100) added 3.33g

Fired to cone 6 in my Ward kiln. Slow cooled.

Colour needs mixing with a blender, appears a bit grainy. Base glaze is pinkish from tin oxide. Poured rather than dipped. Need to repeat this test but concentrating on the lighter oxides, tiles 1, 2 and 3.
I like the way the rutile has added texture especially to the Cobalt corner.