Floating Blue original vs Alberta Slip and Ravenscrag versions

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Floating Blue Original Cone 6 Glaze

Code #

G2826R

P Materials Amt
Gerstley Borate 27.000 26.81%
Nepheline Syenite 47.900 47.57%
EPK 5.500 5.46%
Silica 20.300 20.16%
P Additions
* Iron Oxide Red 2.000 1.99%
* Rutile 4.000 3.97%
* Cobalt Oxide 1.000 0.99%

Total:107.70

Auto Unity Formula + Analysis

CaO 0.41 5.54%
MgO 0.10 0.99%
K2O 0.10 2.31%
Na2O 0.38 5.74%
(KNaO) 0.49
TiO2 0.00 0.05%
P2O5 0.00 0.04%
B2O3 0.43 7.19%
Al2O3 0.55 13.39%
SiO2 3.84 55.50%
Fe2O3 0.01 0.20%

Ratios

Si:Al: 7.0:1
SiB:Al: 7.8:1
R2O:RO: 0.5:0.5

Expansion

7.6 (Molar:7.4)

LOI

9.1

Cost

0.00 per kg

Notes

*This recipe has been used for many decades. Its secret is the high melt fluidity (because Gerstley Borate is such an active melter) and the colorant addition. The rutile variegates the color imparted by the iron and cobalt.

Anyone who has used this glaze will testify to the fact that it is "fickle" as Chappell notes (this is an understatement, see above). He makes a number of recommendations on using this recipe: Use distilled or low mineral water, force all material through an 80 mesh screen, stir thoroughly before and during use to prevent settling out of the iron content, apply the thickness of a dime, fire to cone 6 oxidation exactly, and cool normally. One interesting comment Chappell makes is: "Don039;t substitute any other chemicals for those given". Since that is exactly what we plan to do I might also comment that we have had success at lower temperatures and slower cooling should enhance the effect.

People who use this glaze employ a variety of methods to increase the variation of surface color (i.e. stippling a second layer, brushing a wash of another coloring oxide, double dipping, applying a wash of rutile, etc.).

This recipe is coming to end-of-life since Gerstley Borate (GB) will soon be unavaiable. While substitutes are available it is better to source the B2O3 from frits (a classic example of the value of glaze chemistry).

This calculates to a very high thermal expansion, crazing is likely.
The high Gerstley Borate content means it is likely to gel.

Pictures

G2826R Floating Blue Original Recipe glaze sample

G2826R Floating Blue melt flow test

Compares Gerstley Borate and Boraq 2
This is a good recipe for comparing Gerstley Borates substitutes.

Alternate Code Number:G2587

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Floating Blue Original Cone 6 Glaze" id="67502" key="L8Brh6hQ" date="2023-07-03" codenum="G2826R" picturebasename=""> <recipelines> <recipeline material="Gerstley Borate" amount="27.000" tolerance=""/> <recipeline material="Nepheline Syenite" amount="47.900" tolerance=""/> <recipeline material="EPK" amount="5.500" tolerance=""/> <recipeline material="Silica" amount="20.300" tolerance=""/> <recipeline material="Iron Oxide Red" amount="2.000" added="true"/> <recipeline material="Rutile" amount="4.000" added="true"/> <recipeline material="Cobalt Oxide" amount="1.000" added="true"/> </recipelines> </recipe> </recipes>

Born: 2000-12-21, Modified: 2023-07-03 12:54:57

Ravenscrag Floating Blue

Code #

G2917

P Materials Amt
Ravenscrag Slip 40.000 36.70%
Ravenscrag Slip 1000F Roast 39.000 35.78%
Ferro Frit 3134 20.000 18.35%
Ferro Frit 3124 10.000 9.17%
P Additions
* Iron Oxide Red 2.000 1.83%
* Cobalt Oxide 1.000 0.92%
* Rutile 4.000 3.67%

Total:116.00

Auto Unity Formula + Analysis

BaO 0.00 0.22%
CaO 0.68 12.42%
MgO 0.10 1.27%
K2O 0.08 2.31%
Na2O 0.14 2.81%
(KNaO) 0.22
TiO2 0.01 0.29%
B2O3 0.24 5.44%
Al2O3 0.32 10.70%
SiO2 3.06 59.62%
Fe2O3 0.01 0.62%

Ratios

Si:Al: 9.5:1
SiB:Al: 10.2:1
R2O:RO: 0.2:0.8

Expansion

7.1 (Molar:6.9)

LOI

4.3

Notes

*This is also known as GR6-M at PlainsmanClays.com.

It was made by simply adding the three colorants to the GR6-A Ravenscrag base recipe. Later, 10% frit 3124 was introduced to increase melt fluidity (a secret of the original to the floating effect). Curiously, the B2O3 and KNaO contents are much lower, yet this still produces the same result!

This produces a much better slurry than the Gerstley Borate based traditional floating blue. This works well on M340, even better on M390. It is more transparent and has less floating effect on porcelain.

If grit forms on rims of mugs, you may need to ball mill the glaze. Or sieve it at 80 mesh.

We mix this as a slurry using the same procedure as for GR6-A base recipe.

Batch Ticket Notes

For brushing version:
340 powder
440 water
5 CMC
5 Veegum
Brushing version Oct 2022 used Frit f-12 instead of 3134.

Pictures

Ravenscrag vs. Alberta Slip floating blues at cone 6

Usable, reliable, non-crazing floating blue glazes are difficult to achieve at cone 6. Not these, they pass all the tests yet fire like the original classic G2826R floating blue from David Shaner. Both have been applied at moderate thickness on Plainsman M325 (using a slurry of about 1.43-1.45 specific gravity, higher values end up getting them on too thick). The Ravenscrag version (left) highlights contours better (the edges are black because of the black engobe underneath). It also produces the blue color whether or not the kiln is slow-cooled (although drop-and-hold PLC6DS schedule usually fires more blue). The Alberta Slip version has zero cobalt so it is less expensive to make (but it does require the C6DHSC slow-cool firing schedule). It produces a deeper color over the L3954F black engobe on these pieces. Both of these produce a wide range of effects with different thicknesses, bodies and firing schedules.

Ravenscrag Floating Blue on M370 Cone 6

G2917 RavenBlue cooled slowly, quickly

Rim grit on Ravenscrag glaze not sieved to 80 mesh

Ravenscrag is processed at 42 mesh so particles can disrupt a glaze surface if it is applied or runs very thin.

G2917 Raven blue at cone 7 on P6953 M325

GR6-M cooled quickly, slowly

The left mug was fired using our drop-and-soak PLC6DS, the other with the slow-cool C6DHSC schedule.

Ravenscrag Floating blue as brushing glaze

This can be made into a pint (500ml) of brushing glaze with 340g powder, 5g CMC gum and 5g of Veegum. Blender mixing is a must to get the gelled consistency.

G2917 floating blue vs. Amaco PC-20

The PC-20 Rutile Blue is on the left. It has higher melt fluidity and more white crystallization. G2917 could be altered by substituting some or all of the rutile for titanium dioxide.

Alternate Code Number:GR6-M

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Ravenscrag Floating Blue" id="60534" key="hPHujYHE" date="2023-07-20" codenum="G2917" picturebasename=""> <recipelines> <recipeline material="Ravenscrag Slip" amount="40.000" tolerance=""/> <recipeline material="Ravenscrag Slip 1000F Roast" amount="39.000" tolerance=""/> <recipeline material="Ferro Frit 3134" amount="20.000" tolerance=""/> <recipeline material="Ferro Frit 3124" amount="10.000" tolerance=""/> <recipeline material="Iron Oxide Red" amount="2.000" added="true"/> <recipeline material="Cobalt Oxide" amount="1.000" added="true"/> <recipeline material="Rutile" amount="4.000" added="true"/> </recipelines> </recipe> </recipes>

Born: 2013-08-30, Modified: 2023-07-20 09:37:17

Alberta Slip Floating Blue

Firing schedule is important to develop floating effects

Code #

G2908A

Materials Amt
Alberta Slip 40.000
Ferro Frit 3134 20.000
Alberta Slip 1000F Roasted 40.000
Additions
Rutile 4.000

Total:104.00

Auto Unity Formula

CaO 0.48
MgO 0.24
K2O 0.09
Na2O 0.19
(KNaO) 0.28
TiO2 0.15
B2O3 0.20
Al2O3 0.39
SiO2 2.70
Fe2O3 0.08

Ratios

Si:Al: 7.0:1
SiB:Al: 7.5:1
R2O:RO: 0.3:0.7

Expansion

7.9 (Molar:7.5)

LOI

4.9

Notes

*This is also known as GA6-C at PlainsmanClays.com.

This requires the C6DHSC or similar firing schedule.

We have tested it using Fusion Frit F-12 instead of Ferro Frit 3134 with good results.

We mix this as a slurry using the same procedure as for the GA6-B base recipe.

Pictures

Ravenscrag vs. Alberta Slip floating blues at cone 6

Usable, reliable, non-crazing floating blue glazes are difficult to achieve at cone 6. Not these, they pass all the tests yet fire like the original classic G2826R floating blue from David Shaner. Both have been applied at moderate thickness on Plainsman M325 (using a slurry of about 1.43-1.45 specific gravity, higher values end up getting them on too thick). The Ravenscrag version (left) highlights contours better (the edges are black because of the black engobe underneath). It also produces the blue color whether or not the kiln is slow-cooled (although drop-and-hold PLC6DS schedule usually fires more blue). The Alberta Slip version has zero cobalt so it is less expensive to make (but it does require the C6DHSC slow-cool firing schedule). It produces a deeper color over the L3954F black engobe on these pieces. Both of these produce a wide range of effects with different thicknesses, bodies and firing schedules.

GA6-C glaze on M390 dark stoneware

GA6-C floating blue on M370 whiteware

GA6-C on M340 buff stoneware

GA6C Floating Blue at cone 5R

Cone 5R.

Cooling is critical for GS6-C

Left: GA6-C fired using the PLC6DS schedule. Right: The same glaze fired using the C6DHSC slow cool schedule. Both are Plainsman Coffee clay.

AB slip floating blue, slow cool down

May have applied to thick, ran a bit and blue colour was not well developed.

Links with Schedules

To: Plainsman Cone 6ox drop-hold-slow-cool

Alternate Code Number:MA6C

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Alberta Slip Floating Blue" keywords="Firing schedule is important to develop floating effects" id="36534" key="mgksgJ21" date="2024-02-14" codenum="G2908A"> <recipelines> <recipeline material="Alberta Slip" amount="40.000" tolerance=""/> <recipeline material="Ferro Frit 3134" amount="20.000" tolerance=""/> <recipeline material="Alberta Slip 1000F Roasted" amount="40.000" tolerance=""/> <recipeline material="Rutile" amount="4.000" added="true"/> </recipelines> </recipe> </recipes>

Born: 2006-08-30, Modified: 2024-02-14 20:44:59