Sunday, 8 April 2018

Cone 6 colour tests

Date: 9 April 2018
Clay: Keanes Stoneware 7

Following on from last week's Cone 6 tests. Adding different colour oxides in 50-50 mixture for HP and four different colour tests for 14Pine.

Colour tests 50:50 grid

Mixed up 250gms of Base Glaze and then divided it volumetrically into 5 equal batches.
Started the five test pots with double strength as they will be diluted by 50% when combined with another pot.

Added colourants as below:
A - 3% Copper Carbonate
B - 2% Cobalt Carbonate
C - 6% Red Iron Oxide
D - 12% Rutile flour
E - 8% Titanium Dioxide

glaze test colours

14 Pine Street
Colour variations

Mixed up 200gms Base Glaze and divided it into four batches.
Added these colourants
1 - 0.375% Cobalt Carbonate, 6% rutile
2 - 0.25% Cobalt Carbonate, 3.5% Titanium dioxide, 2.25% Copper Carbonate
3 - 0.25% Cobalt Carbonate, 2.25% Copper Carbonate
4 - 0.25% Cobalt Carbonate, 3% Red Iron Oxide

14P colour mixes
Kiln colour

Cone 6 tests

Three tests in recently fixed kiln.

Date: 7th March 2018
Clay: Keane's Stoneware 7

Hp glaze
HP shade

Hopeful Potter Matte

40      Potash Feldspar
20      Whiting
25      Eckalite (China Clay)
15      Silica

John Post Calcium Matte [JP. JPSM]

30.2    Ball Clay FX (Kentucky OM)
5.7      Frit 3134
32.5    Nepheline Syenite
16.3    Wollastonite
4.9      Whiting
10.4    Silica (Flint)

14 Pine
4.03     Frit 3124
28.20   Potash Feldspar
16.11   Whiting
19.17   Eckalite
32.50   Silica

Love them all.
Surprised JP wasn't more matte.
HP is lovely, read later its for ^8? Seems okay though, I"m going to perservere.
14 is taken from my Currie grid test at Pine Street. Initially I'd chosen another square but later it crazed so I went with another mix that hadn't.

Now to test with colour!

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.