N505 and Val Cushing Satin White #71 recipes Vs G2934 and G1214Z

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What are the pros and cons of the popular base recipes, are they better or worse that G2934 and G1214Z


Project Name

N505, Cushing Satin #71 matte cone 6 glazes

Project Codenumber

UnAssigned

Notes

This project compares N505 (our code number G3955) with our commonly used G2934 MgO matte and G1213Z1 CaO mattes.

Some obvious things can be noted about N505:

-N505 contains no silica and very little clay, it is thus surprising that it even works at cone 6. Low SiO2 and Al2O3 generally mean cutlery marking, running - this is a low temperature glaze being fired at cone 6.

-N505 has a lot of Cornwall Stone, that normally means high KNaO and crazing (however it also has lots of MgO to keep the thermal expansion down).

-N505 contains magnesium carbonate, it can matte glossy glazes at almost any temperature, simply because the particles don't melt with the glaze and affect its ability to smooth out. The MgO is the matteness mechanism and the MagCarb is helping stablize against running. The degree of matteness of N505 is very likely to change with different firing schedules.

Satin White #71 has a more promising chemistry (higher SiO2 and Al2O3). It melts to a satin surface with much less frit or Gerstley Borate than normal, thus being lower in cost.

N505 Base Satin White - Opaque

Code #

G3955

Materials Amt
Dolomite 12.000 11.32%
Gerstley Borate 14.000 13.21%
Wollastonite 10.000 9.43%
Fusion Frit F621/19 8.000 7.55%
Cornwall Stone 46.000 43.40%
EPK 10.000 9.43%
Magnesium Carbonate 6.000 5.66%

Total:106.00

Auto Unity Formula

CaO 0.52
MgO 0.34
K2O 0.05
Na2O 0.10
(KNaO) 0.14
B2O3 0.16
Al2O3 0.27
SiO2 1.87

Ratios

Si:Al: 7.0:1
SiB:Al: 7.6:1
R2O:RO: 0.1:0.9

Expansion

7.1 (Molar:6.9)

LOI

13.6

Cost

0.09 per kg

Notes

*This recipe is from page 2 of booklet: 15 Tried & True Cone 6 Glaze Recipes. The Fusion frit used here is the equivalent for Ferro Frit 3124 in the recipe they quote.

This recipe has very very low Al2O3 and also low SiO2. It is a low-temperature glaze being fired at cone 6, it is thus very runny. It was not a matte until someone added that 6% MagCarb, that is crowbarring the surface to matteness (and roughness). When controlled this produces a more interesting surface and is thus popular with artists and potters.

We were actually suspicious that this glaze would have more issues than it actually does. Although the surface is rough and it does mark and stain, it can be cleaned with effort. The low SiO2 suggests it would cutlery mark but it does seem quite hard. However, on the matter of leaching the jury is still out (a stain needs to be added for testing in an acid). Crazing is another likely problem. Our G3924 recipe, although more boring, excels on all four of these tests.

Equal parts water and powder produced a good slurry.

Pictures

P7033 G2934 Cone 6 Matte vs. the N505 recipe

The G2934 (left) is not running as much as normal, but the melt looks and works great, the surface is very functional and smooth. The difference could be the use on the Fusion frit instead of Ferro.

P7033 G2934 production run vs. G3955

G2934 (right), G3955 (left).
Cone 6 standard drop-and-hold firing.
Results are fantastic, the G2934 surface is perfect.
The G3955 thickens markedly on an contour and runs (thickness of application is light so it could easily have run much more on a longer dip).

G2934 (left) vs G3955 (right) mattes at cone 6

The G2934 is very smooth and this felt marker cleaned off effortlessness. The other required scrubbing and could not be removed completely.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="N505 Base Satin White - Opaque" id="183847" key="B1fCBmaw" date="2022-11-14" codenum="G3955"> <recipelines> <recipeline material="Dolomite" amount="12.000" tolerance=""/> <recipeline material="Gerstley Borate" amount="14.000" tolerance=""/> <recipeline material="Wollastonite" amount="10.000" tolerance=""/> <recipeline material="Fusion Frit F621/19" amount="8.000" tolerance=""/> <recipeline material="Cornwall Stone" amount="46.000" tolerance=""/> <recipeline material="EPK" amount="10.000" tolerance=""/> <recipeline material="Magnesium Carbonate" amount="6.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2020-09-11, Modified: 2022-11-14 11:15:56

Cone 6 Magnesia Matte Base

Code #

G2934

Materials Amt
Ferro Frit 3124 19.400 19.01%
EPK 18.300 17.93%
Dolomite 23.500 23.03%
Silica 26.960 26.42%
Calcined Kaolin 13.900 13.62%

Total:102.06

Auto Unity Formula + Analysis

CaO 0.54 9.77%
MgO 0.39 5.06%
K2O 0.01 0.19%
Na2O 0.06 1.23%
(KNaO) 0.07
TiO2 0.00 0.07%
P2O5 0.00 0.04%
B2O3 0.12 2.61%
Al2O3 0.45 14.85%
SiO2 2.71 52.42%
Fe2O3 0.00 0.14%

Ratios

Si:Al: 6.0:1
SiB:Al: 6.2:1
R2O:RO: 0.1:0.9

Expansion

5.8 (Molar:5.7)

LOI

13.6

Cost

0.17 per kg

Notes

*This matte recipe was developed at Plainsman Clays. It descends from a high-dolomite recipe that was originally used to compare shipments of dolomite for consistency. In our standard firings this recipe produces both good mattenss and a very functional surface coupled with very low chance of crazing. It is not as interesting as reactive mattes but this is better for functional and durable surfaces. This is also adjustable, the degree of matteness can be controlled by blending in a glossy.

WARNING: The degree-of-matteness is very dependent on cooling rate in the kiln. Fast cooling (e.g. our PLC6DS firing schedule in a lightly-loaded or smaller kiln) produces a silky matte or even glossy surface. Slower cooling (e.g. a heavily loaded kiln or the C6DHSC schedule) may produce a matter surface than you need (which is more subject to cutlery marking). Control the degree of mattness by either adapt the firing curve or blending in some glossy G2926B (simply the slurries pouring together, volumetrically is a good way to determine the ratio needed).

https://plainsmanclays.com/g2934 documents this recipe using a variety of stains.

Pictures

G2934 with Hemlock Green, Pansy Purle Stains

10 gram balls have been melt down onto a tile at cone 6.
Top: G2934 with normal flow
Left: 8% 6213 Hemlock Green. Needs significant flux.
Right: 8% 6305 Violet stain. Flowing a little less, needs a little flux.

True mattes should still be matte if overfired

The G2934 is a high-MgO matte, it melts well and does not cutlery mark or stain easily. As evidence that it is a true matte, notice that it is still matte when fired to cone 7 or 8. VC71, while having a similar pleasant silky matte surface at cone 6, converts to a glossy if fired higher (suggesting that its cone 6 matteness is due to incomplete melting). For the same reason the VC71, it is whiter in color (but as soon as it begins to melt and have depth the color darkens).

G2934 + 5% Titanium thinner/thicker on M390

Incredible cone 6 speckle body with G2934 matte glazes

This clay, L4115J3S, a Plainsman 3D-based body, fires vitreous and dense, yet there is no hint of bloating. With these matte glazes very durable and functional pieces are produced.

Outside glaze on both is G2934W (adds 10% zircopax). In our C6DHSC firings this produces as matte a surface as is possible without having excessive staining problems. To add a little gloss we blend in 15% of the G2926B Glossy clear.

Inside glazes:
Left mug: L4423A (85:15 mix of G2934 matte/G2926B clear glossy). It does not contain any zircopax.
Right mug: G2926B ball milled glossy, producing a striking visual yet highly functional surface.

These mugs look as close to cone 10R dolomite-glazed ware as we have ever seen! Especially the L4423A recipe

Melt flow comparison: G2934 with Frit 3124, Frit F-19

Fusion Frit F-19 is giving a more fluid melt.

The difference cooling-rate makes

These are the G2934 black glaze at cone 6. The piece on the left was fired using the C6DHSC firing schedule (drop-and-hold at 2100F then 150F/hr to 1400F). The one on the right was fired using the PLC6DS schedule (drop-and-hold at 2100F then free-fall from there). The slow cool gives the glaze on the left time to crystallize, creating a stony matte.

G2934 Cone 6 Matte + 4% iron oxide

Left: PLC6DS firing
Right: C6DHSC firing

URLs

Prepared public do..om Plainsman Clays

Typecodes

C6-Cone 6 Glazes

Alternate Code Number:MG6CDM

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 6 Magnesia Matte Base" id="56852" key="wnPxBauh" date="2024-03-08" typecodes="C6" codenum="G2934" picturebasename=""> <recipelines> <recipeline material="Ferro Frit 3124" amount="19.400" tolerance=""/> <recipeline material="EPK" amount="18.300" tolerance=""/> <recipeline material="Dolomite" amount="23.500" tolerance=""/> <recipeline material="Silica" amount="26.960" tolerance=""/> <recipeline material="Calcined Kaolin" amount="13.900" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2014-03-21, Modified: 2024-03-08 20:40:00

Cone 6 Calcium Matte v2

Code #

G1214Z1

Materials Amt
Wollastonite 27.000 26.73%
Ferro Frit 3124 36.000 35.64%
EPK 20.000 19.80%
Silica 5.000 4.95%
Calcined Kaolin 13.000 12.87%

Total:101.00

Auto Unity Formula

CaO 0.89
Na2O 0.10
(KNaO) 0.10
B2O3 0.19
Al2O3 0.46
SiO2 2.50

Ratios

Si:Al: 5.5:1
SiB:Al: 5.9:1
R2O:RO: 0.1:0.9

Expansion

7.0 (Molar:7.1)

LOI

2.9

Cost

0.19 per kg

Notes

*This is an adjustment to the original G1214Z recipe. The chemistry of this is the same, but the 37 raw kaolin in the original has been split to a combination of raw:calcined kaolin to reduce drying shrinkage (preventing cracking as it dries and crawling during firing). If unavailable, you can make your own calcined kaolin by roasting the powder in a container in a bisque firing.

For 3000 grams we use 2600 water to get 1.45 specific gravity and good flow properties (no Epsom salts should be needed to gel the slurry, it is naturally thixotropic).

Pictures

3 opacifiers on Coffee Clay, M390 in G1214Z

G1214Z2 on M340, M390 at cone 6

G1214Z at cone 6 with 10% Zircopax and 5% tin oxide

The body is Plainsman M390. The firing schedule is Plainsman PLC6DS. The tin is on the right.

Alternate Code Number:GS6-B

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 6 Calcium Matte v2" id="156545" key="vLL9D86n" date="2023-06-19" codenum="G1214Z1" picturebasename=""> <recipelines> <recipeline material="Wollastonite" amount="27.000" tolerance=""/> <recipeline material="Ferro Frit 3124" amount="36.000" tolerance=""/> <recipeline material="EPK" amount="20.000" tolerance=""/> <recipeline material="Silica" amount="5.000" tolerance=""/> <recipeline material="Calcined Kaolin" amount="13.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 1998-04-21, Modified: 2023-06-19 19:38:59

Val Cushing Satin White #71

Code #

G3892

Materials Amt
Talc 9.000 8.91%
Whiting 16.000 15.84%
Ferro Frit 3124 9.000 8.91%
Custer Feldspar 40.000 39.60%
EPK 10.000 9.90%
Silica 16.000 15.84%
Bentonite 1.000 0.99%

Total:101.00

Auto Unity Formula

CaO 0.56
MgO 0.22
K2O 0.13
Na2O 0.09
(KNaO) 0.22
B2O3 0.05
Al2O3 0.35
SiO2 2.98

Ratios

Si:Al: 8.6:1
SiB:Al: 8.8:1
R2O:RO: 0.2:0.8

Expansion

7.2 (Molar:6.7)

LOI

9.1

Cost

0.27 per kg

Notes

*A long time favorite cone 6 matte glaze recipe.

Pictures

Val Cushing #71 at cone 6

Fast cool, drop and soak.
The surface is similar to G2934Y

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Val Cushing Satin White #71" id="161479" key="vA4aajR9" date="2023-01-19" codenum="G3892" email="gallagher.peggy@gmail.com"> <recipelines> <recipeline material="Talc" amount="9.000" tolerance=""/> <recipeline material="Whiting" amount="16.000" tolerance=""/> <recipeline material="Ferro Frit 3124" amount="9.000" tolerance=""/> <recipeline material="Custer Feldspar" amount="40.000" tolerance=""/> <recipeline material="EPK" amount="10.000" tolerance=""/> <recipeline material="Silica" amount="16.000" tolerance=""/> <recipeline material="Bentonite" amount="1.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2019-08-26, Modified: 2023-01-19 10:52:02