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White Cone 6 Engobe, New Alberta Slip base glazes for Plainsman M340, M390

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

Make flawless cone 6 ware with clean functional surfaces, even on red burning bodies, using these recipes and this firing schedule.


White Engobe for M390, M340

Code #

L3954B

Batch #

3

Materials Amt
Nepheline Syenite 18.000 10.27%
Silica 15.000 8.56%
M23 Ball Clay 54.000 30.82%
Zircopax 10.000 5.71%
Bentonite 3.000 1.71%
*Mason 6336 Stain 0.200 0.11%
Water 75.000 42.81%

Total:175.20

Notes

More information on this recipe (especially mixing instructions) can be found on its https://plainsmanclays.com/data/index.php?product=12940page/a> at http://plainsmanclays.com.

This recipe has been tuned to have about the same drying and fired shrinkage as the target clay bodies (Plainsman M390, M340). It has more Zircopax, more stain and less flux than previous ones. Fired shrinkage was matched using bi-clay strips (see below). Thus, this is not vitreous like a porcelain.

To prepare the slurry mix equal parts water and powder and fine tune thixotropy using Epsom Salts and Darvan (until it is gelled the right amount to stay on ware without dripping after dipping or going on to thick).

The color is whiter than previous trials (because of the zircopax), but some might prefer a little more benefit from more blue stain. Use the 6336 stain, we have found that others agglomerate and cause specking).

A black version of the stain can be made by substituting the Zircopax for burnt or raw umber (same percentage). Or black stain (about 5%). Of course, for the darkest possible black use stain and at a higher percentage.

2000 clay, 2000 water produces 1.44 specific gravity, however we recommend about 1.48. You must use Darvan to thin it or the specific gravity will be too low.

URLs

Information about .. Reference Library

Pictures

L3954B Very sensitive to over deflocculation

Only 3 drops of darvan in 3/4 gallons of slip fixed the problem on the left. The slurry was over flocculated using Epsom Salts.

L3954B engobe:red stoneware biclay cones

The white engobe was prepared in plastic form and rolled and laminated with the red body. The thin strips were dried and fired to cone 6 to find incompatibilities in drying and firing shrinkage.

Results are very good, slight curling toward M390 (the Plainsman red burning body) on drying, a little more toward the white slip on firing.

M390:3954B engobe BiClay strips after drying

These were laminated in plastic form. Two were dried red body side up, two with the engobe side up. Results are very flat, very good drying shrinkage fit.

10% black and red stains in L3954B Engobe

Black is Mason 6666. Although color is good, Mason 6600 is the recommend one for bodies.
Red is Mason 6021. Much more will be required to get good color.

L3954B with Burnt Umber and Black Stain

Both replace the 10% zircopax with a black pigment. They darken the engobe to near black. But the stain version (Mason 6600) on the right fires blacker and develops the color of this rutile glaze (Alberta Slip rutile blue) much better. It also produces a perfect glass surface whereas the Umber version on the left develops some pinholing in the inside glaze (GA6A Alberta Slip base).

Testdata

SHAB - Shrinkage/Absorption

DLEN FLEN FWT BWT CONE DSHR FSHR ABS
1 92.89 86.63 40.38 41.3 6.0 7.1% 6.7% 2.3%

EBCT - Engobe Body Compatibility Test

MATA MATB BNDR BNFR BCON
1 M390 L3954B 1.5mm/A 3.0mm/B 6.0

Born: 2016-12-12, Modified: 2017-09-17 07:47:51

Alta Slip Cone 6 Base w/Frit 3249

Code #

L3500E

Materials Amt
Alberta Slip 40.000 21.05%
Ferro Frit 3249 20.000 10.53%
Alberta Slip Calcined 40.000 21.05%
Water 90.000 47.37%

Total:190.00

Auto Unity Formula

CaO 0.33
MgO 0.47
K2O 0.10
Na2O 0.10
(KNaO) 0.20
TiO2 0.01
B2O3 0.27
Al2O3 0.50
SiO2 2.93
Fe2O3 0.08

Si:Al Ratio

5.9:1

SiB:Al Ratio

6.4:1

Calculated
Expansion

6.5

LOI

1.9

Cost

0.00 per kg

Notes

This is part of a program to compare the results of fluxing Alberta Slip for cone 6 using 4 different frits (3134, 3124, 3195 and 3249).
Frit 3249 is a low expansion frit, it reduces the expansion of the Alberta Slip base such that it works well on even P300 porcelain.

Even though this recipe calculates to a low Si:Al ratio and a very high MgO level (both indicative of a matte glaze), this one fires ultra glossy.

2700 water, 3000 dry gives 1.43

Pictures

GA6A base using Frit 3249 and 3195 on buff body

The body is buff burning Plainsman M340 (cone 6). The amber colored glaze is 80% Alberta Slip (raw:calcine mix) with 20% of each frit. The white engobe on the inside of mug 1 is L3954A (also glazed inside using transparent G2926B). These frits are producing an amber gloss glaze of high quality. On the outside of mug 1 we see it this glaze on the white slip until midway down, then on the bare buff clay. These mugs are fired using a drop-and-soak firing schedule.

P300 and M370 mugs with GA6A Alberta Slip (using Frit 3249)

Rather than the normal 80:20 AlbertaSlip:Frit3134 recipe, this one substitutes Frit 3249 (super low expansion). The glaze is less runny and even glossier. These are fired at cone 6 in a cool-and-soak firing. They survived boiling water:ice water tests without crazing. The finish is dazzling, a brilliant amber glass with no defects and perfectly even coverage. Of course, the iron in the glass prevents the colors of the blue underglaze from showing through. But the black is great.

Melted glaze for thermal expansion test has bubbled

GA6A base using Frit 3249 - P300 cone 6

Surface is flawless. Drop and soak firing.

L3500 Frit 3249, 3195, 3124 ingots ready to fire

9 12gram balls in each refractory crucible.

GA6-A glaze with four frits (flow tests)

Four frits in GA6-A at cone 6

Frit 3195 (top left), 3134 (top right)
3214 (bottom left), 3249.
10 gram melt balls.

Born: 2006-08-30, Modified: 2017-08-31 13:06:56

Alta Slip Cone 6 Base w/Frit 3195

Code #

L3500C

Materials Amt
Alberta Slip 40.000 21.05%
Ferro Frit 3195 20.000 10.53%
Alberta Slip Calcined 40.000 21.05%
Water 90.000 47.37%

Total:190.00

Auto Unity Formula

CaO 0.44
MgO 0.28
K2O 0.11
Na2O 0.17
(KNaO) 0.27
TiO2 0.01
B2O3 0.22
Al2O3 0.51
SiO2 3.14
Fe2O3 0.08

Si:Al Ratio

6.1:1

SiB:Al Ratio

6.5:1

Calculated
Expansion

7.2

LOI

1.9

Cost

0.00 per kg

Notes

This is part of a program to compare the results of fluxing Alberta Slip for cone 6 using 4 different frits (3134, 3124, 3195 and 3249).
3249 and 3195 both produce a brilliant, stunning ultra gloss result. They work on porcelains, buff and dark stonewares. On M390 they produce a micro-bubble-free glass that really showcases the rich color of the body below.

This glaze is more stable, less runny that GA6A, yet is just as glossy.

Links with Schedules

To: Plainsman Cone 6ox drop-hold

Pictures

GA6A base using Frit 3249 and 3195 on buff body

The body is buff burning Plainsman M340 (cone 6). The amber colored glaze is 80% Alberta Slip (raw:calcine mix) with 20% of each frit. The white engobe on the inside of mug 1 is L3954A (also glazed inside using transparent G2926B). These frits are producing an amber gloss glaze of high quality. On the outside of mug 1 we see it this glaze on the white slip until midway down, then on the bare buff clay. These mugs are fired using a drop-and-soak firing schedule.

GA6A Alberta Slip base using Frit 3124, 3249 and 3195

The body is dark brown burning Plainsman M390 (cone 6). The amber colored glaze is 80% Alberta Slip (raw:calcine mix) with 20% of each frit. The white engobe on the inside of two of the mugs is L3954A (those mugs are glazed inside using transparent G2926B). The Alberta Slip amber gloss glaze produces an ultra-gloss surface of high quality on mugs 2 and 3 (Frit 3249 and 3195). On the outside we see it this glaze on the white slip until midway down, then on the bare red clay. The amber glaze on the first mug (with Frit 3124) has a pebbly surface that is not working nearly as well. These mugs are fired using a drop-and-soak firing schedule.

Untitled

M390 clay with white engobe inside

L3954A engobe inside, clear glazed inside (G2926B). Outside is GA6A base using Frit 3195 instead of 3134. The result is a glossier more defect free glass.

L3500C 3195 Alberta Slip glaze does not crystallize

Melted glaze for thermal expansion test has bubbled

Alberta Slip on P300 with Frits 3134, 3124, 3249, 3195

This porcelain can be difficult to fit glazes to.
Thermal shock tested: 300F to ice water
Frit 3134 version (top left) crazing.
3124 slight crazing (top right).
3249 and 3195 (bottom) are uncrazed.
3134 version has the cleanest surface but 3195 is close behind.
These were not slow cooled or drop-soaked during firing.

P300 cylinder with AlbertaSlip:Frit 3195 glaze

Cone 6. Flawless results. Rutile firing schedule.

L3500C GA6A Base using Frit 3195 does not make rutile blue

Left is the standard GS6A with Frit 3134. Right has the rutile also, and was in the same firing, but the higher Al2O3 prevents its variegating action.

L3500 Frit 3249, 3195, 3124 ingots ready to fire

9 12gram balls in each refractory crucible.

Alberta Slip as a Celadone at cone 6 and 10R

Left: Alberta Slip 80, Frit 3195 20. On Plainsman M370.
Right: Alberta Slip/Ravenscrag Slip 50:50 mix. On Plainsman P700.

Born: 2006-08-30, Modified: 2017-09-21 17:09:49

Firing Schedule Name

Plainsman Cone 6ox drop-hold

Cone-Art 2818D, exhaust fan on at start of firing

Degrees (Fahrenheit or Celcius)

F

Schedule Type

Rate

Start Time and Temperature

10:00 pm at 70F

Program

Step Degrees/Hr Temperature
Monitor
Hold
Time
Accumulated
hrs:min
Time Note
1 300 240 60 1:34 11:34 pm
2 350 2080 15 7:04 5:04 am
3 108 2180 15 8:14 6:14 am
4 500 1910 30 9:16 7:16 am 270F drop
5 150 1400 12:40 10:40 am 2195 in large kiln

Notes

Plainsman kiln cone 6: 2188 Jan 2016 as verified by cones.

Use for defect free glazes that need to crystallize during cooling (e.g. rutile blues). And to get defect free glaze surfaces in others.

If the kiln is full, lengthen the first step hold time to drive out all residual or remaining water from body and glaze (depending on the ventilation in your kiln). This schedule assumes that a good bisque has been done.

If cone 6 still does not completely fall (e.g. you fire heavy loads), increase the hold time in Step 3 by 5 minute increments.