Creating a while-on-black oil spot glaze effect at cone 6 oxidation

Share from Insight-live.com (Lab Documentation and Calculation System) by Digitalfire.


Project Name

Simulated Oil Spot Effect (white over black)

Project Codenumber

UnAssigned

Notes

Challenges to creating a layered oil-spot glaze effect:

Choose a good black. Theoretically it needs to be melt-fluid and mobile. In this project I compared G3914A, G2926BB and G2934BL. But only one of them worked, the Alberta Slip version. At first I thought this was because it has a higher LOI. But it does not, it is only 3.5%. Then I thought it was because it has more coarser particles (because of the Alberta Slip), but after ball milling it continued to work?

Choose a good white: Theoretically, it needs to have a higher surface tension. Yet, as you will see in the notes for G3912A, I mistakenly ended up with one of low surface tension. Yet it still worked!

So I am going to do more work on this to try to understand why the G3912A/G3914A combination works and the others do not.

Pictures

The effect I am seeking

The surface tension on a white glaze floating on a black under glaze pulls it into islands revealing the color below.

Surface Tension White Tin

Code #

G3912A

Materials Amt
Strontium Carbonate 23.529
Ferro Frit 3195 15.294
Ferro Frit 3110 15.294
EPK 20.000
Silica 25.882
Additions Amt
Tin Oxide 6.000

Total:106.00

Auto Unity Formula

CaO 0.18
K2O 0.02
Na2O 0.20
(KNaO) 0.21
SrO 0.60
B2O3 0.21
Al2O3 0.37
SiO2 3.33
SnO2 0.15

Ratios

Si:Al: 9.1:1
SiB:Al: 9.7:1
R2O:RO: 0.2:0.8

Expansion

7.0

LOI

10.0

Cost

0.19 per kg

Notes

*This was calculated from G2934, replacing CaO and MgO for SrO, to increase the surface tension of the melt and add LOI to create bubble turbulence. I later realized the SrO would actually reduce the surface tension (high MgO is the key to high surface tension so I should have just used the original G2934Y recipe with added zircopax). Yet this worked anyway in my simulated oil-spot glaze project.

The change has produced a non-typical chemistry (0.60 SrO would be highly unusual). However it does behave similarly to CaO (and high-CaO is very normal in glazes). However this recipe sources plenty of Al2O3 and SiO2 and it is melting very well, so there is no reason to believe it would leach.

We tried 4,5,6,7% tin. There appeared to be no benefit to going beyond 6.

Initial mix was 400 water and 500 powder. It was too thin but epsom salts gelled it.

Pictures

G3912A with 4,5,6,7% tin oxide

Fired cone 6 PLDSSC firing.

Cone 6 V-359 engobe, G3912A glaze

At cone 6 this is more fluid than expected. However there is plenty of bubbling from the strontium, this is beneficial to the oil-spot effect.

G3912A on G2934Y, G2926B, G3914A blacks

Cone 6. Clearly this white is sensitive to the black glaze it is on. It is not working on the G2934Y or G2926B.

Untitled

G3914A black with G3912A overglaze - 4-7% tin

The first black one (with 4% tin overglaze), only has 3% black stain.

G3912A on G3914A at cone 8

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Surface Tension White Tin" id="186948" key="AyuvTeL4" date="2021-03-19" codenum="G3912A"> <recipelines> <recipeline material="Strontium Carbonate" amount="23.529" tolerance=""/> <recipeline material="Ferro Frit 3195" amount="15.294" tolerance=""/> <recipeline material="Ferro Frit 3110" amount="15.294" tolerance=""/> <recipeline material="EPK" amount="20.000" tolerance=""/> <recipeline material="Silica" amount="25.882" tolerance=""/> <recipeline material="Tin Oxide" amount="6.000" added="true"/> </recipelines> </recipe> </recipes>

Born: 2018-01-29, Modified: 2021-03-19 09:03:55

Alberta Slip Basecoat Black #2

Code #

G3914A

Materials Amt
Alberta Slip 40.000 38.46%
Alberta Slip Roasted 40.000 38.46%
Ferro Frit 3195 20.000 19.23%
*Mason 6600 Black 4.000 3.85%
Additions Amt
Water 88.550 85.14%
Gum Solution 3.450 3.32%

Total:196.00

Auto Unity Formula

CaO 0.45
MgO 0.28
K2O 0.11
Na2O 0.17
(KNaO) 0.27
TiO2 0.01
B2O3 0.23
Al2O3 0.51
SiO2 3.15
Fe2O3 0.08

Ratios

Si:Al: 6.1:1
SiB:Al: 6.6:1
R2O:RO: 0.3:0.7

Expansion

7.2

LOI

4.7

Cost

1,128.93 per kg

Notes

*Initially added 3% Mason 6600 to GA6-B recipe. Increased it to 4% to get better black.
Based on information below, 104 powder, 92 water produces 1.49SG.

This was mixed as a base-coat dipping glaze (for overglazing with decorative colors, thus gum was added).
Initial 40:360 gumsolution:water proportion dried too slowly. Then tried 30:370. Still the same. Finally, used 15:385 gum:water mix and it behaved well. Rounded that to 4:96.

We ball milled it remove some particles of grit (labelled G3914B).

Comments

2021-02-08

Joe: Jan. 8/21
Glaze powder: 1858 gms.
Water/Gum Solution: 1642 gms.
3500 gms. batch total weight.
Let sit over weekend and screened 80 mesh and checked S.G. and found to be 1.49

Pictures

Three cone 6 black glazes

Left: 2926B black (mislabelled as 2917F) G3914A Alberta Slip black. G2934 satin black. The G3914A (#2) has surface variegation that the other two lack (a combination of healed micro-bubbles and precipitation of the black). While the 4% stain might be a little too much, this did survive and overnight lemon-juice test without any visible effect.

G3914A 3% stain with G3912A - 6% tin

G3914A black with G3912A overglaze - 4-7% tin

The first black one (with 4% tin overglaze), only has 3% black stain.

G3912A on G2934Y, G2926B, G3914A blacks

Cone 6. Clearly this white is sensitive to the black glaze it is on. It is not working on the G2934Y or G2926B.

G3914A Black is metallic at cone 6

While only having 4% stain, the surface has a unique metallica and crystalline quality. The full effect requires ball milling.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Alberta Slip Basecoat Black #2" id="188926" key="pfZMAmnx" date="2021-02-11" codenum="G3914A"> <recipelines> <recipeline material="Alberta Slip" amount="40.000" tolerance=""/> <recipeline material="Alberta Slip Roasted" amount="40.000" tolerance=""/> <recipeline material="Ferro Frit 3195" amount="20.000" tolerance=""/> <recipeline material="Mason 6600 Black" amount="4.000" tolerance=""/> <recipeline material="Water" amount="88.550" added="true"/> <recipeline material="Gum Solution" amount="3.450" added="true"/> </recipelines> </recipe> </recipes>

Born: 2020-11-17, Modified: 2021-02-11 10:54:10

G2926B Black

Code #

G2926BB

Notes

*G2926B is out standard transparent glaze for cone 6.

We added 6% Mason 6600 stain, this produces an incredibly rich black. However it does not appear to work well as the underglaze in the oilspot effect using the strontium G3912A overglaze.

Pictures

G2926B Black vs. Low Fire black

While G2926B Black looks impressive at first, when you hold it beside a low temperature glossy black (like Spectrum one) it is not as good. Ball milling would improve that.

G3912A on G2934Y, G2926B, G3914A blacks

Cone 6. Clearly this white is sensitive to the black glaze it is on. It is not working on the G2934Y or G2926B.

XML (to paste into Insight)

Born: 2021-02-03, Modified: 2021-02-08 22:32:48

G2934Y Black

Code #

G2934BL

Notes

*This is a mix of G2934 and G2926B bases (about 35:65).

Pictures

G2934Y black on M370

Cone 6. Drop and soak firing. A beautiful silky, gunmetal black surface. A slow-cool firing would make it more matte.

G3912A on G2934Y, G2926B, G3914A blacks

Cone 6. Clearly this white is sensitive to the black glaze it is on. It is not working on the G2934Y or G2926B.

XML (to paste into Insight)

Born: 2021-02-03, Modified: 2021-02-08 18:23:20