The 20x5 Recipe Has Been Improved

50:30:20 Gerstley Borate Cone 6 base

Total:100.00

Auto Unity Formula

Notes

This is recipe has been around for a long time. It is the base for many others, mainly because of its high melt fluidity (e.g. Butterscotch (Rust) added: 4% rutile, 4% tin oxide and 1% lithium carboante.

This fires with plenty of boron blue and bubble clouding, but that was seen as part of the aesthetic. It has a low thermal expansion and fitted most clay bodies.

Mixing this 50:50 with water produces 1.44 specific gravity, but it will be pure gel. Adding 0.5% Darvan helps to thin it for long enough to dip bisque samples (but the glaze goes on very thin). The slurry re-gels within seconds.

For making flow tester balls this slurry dewaters very slowly on a plaster bat.

GB is a clay, capable of suspending and dry hardening a glaze at only 25% concentration. Yet this has double that plus adds kaolin which would further increase drying shrinkage! It is amazing that it was even possible to make a usable slurry out of this!

Pictures

G2826A vs G2826A1 low test

A1 supplies boron using frit 3134.
Since the frit contains less boron the full B2O3 cannot be supplied and it has a little more Al2O3 and SiO2.
But the A1 has 6 times lower LOI.
G2826A is a good recipe for comparing GB substitutes.

G2826A Gerstley Borate 50:30:20 base as jelly

G2826A on M390 - lots of boron blue

You might think this looks nice. But it comes at a cost (bubbling, jelling, running, cracking on drying, crawling). Boron blue is considered a glaze fault.

That being said, many people like gerstley borate for this very reason.

Fired at 1700F G2826A 50:30:20 GB

Fired at 1700F
G2826A 50:30:20 GB
G2826A1 same chem using frit
G2826A2 50:30:20 using Gill Borate (should be crawling??)
G2826A3 50:30:20 makeover using GillBor
G2826A3-2 same but with calcine kaolin

50:30:20 Frit 3134 cone 6 base

Total:105.00

Auto Unity Formula

Notes

This was a product of substituting Ferro Frit 3134 for Gerstley Borate in the long-time G2826A base transparent recipe. This was originally done in the 1970s.

The result is a poor match of the overall chemistry of the original. The KNaO is doubled, the Al2O3 is 50% higher, the SiO2 25% higher and there is no MgO.

A big downside of this recipe is cost because of the extremely high frit content. This one also has a higher thermal expansion, which means it crazes on some bodies that the original G2826A fitted.

This being said, this recipe has been popular for 50 years or more. It is the base of many, one common one is a bright opal blue made by adding 2-3% cobalt oxide.

An upside of this version, compared to the original 50:30:20 G2926A recipe, is the 20% kaolin that produces a nice slurry that suspends and applies well (rather than the bucket of jelly that the Gerstley Borate produced).

Pictures

Typecodes

RCP-Undefined

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="50:30:20 Frit 3134 cone 6 base" id="63485" key="uNA29Sb4" date="2024-10-02" typecodes="RCP" codenum="77C04E" picturebasename=""> <recipelines> <recipeline material="Ferro Frit 3134" amount="50.000" tolerance=""/> <recipeline material="EPK" amount="30.000" tolerance=""/> <recipeline material="Silica" amount="25.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 1980-01-01, Modified: 2024-10-02 19:20:26

Hansen 20x5 Clear Cone 6 Base Glaze

Total:100.00

Auto Unity Formula + Analysis

Notes

This recipe goes back to the 1980s, it was formulated by Tony Hansen as an alternative to the then popular 77C04E recipe of 50:30:20 frit3134:silica:kaolin.

If you cannot get Frit 3134 but have Gillespie Borate then this recipe, G1214M1, sources the same chemistry:
18 Wollastonite
18 Gillespie Borate
18 EPK
25 Silica
22 Minspar 200

Common Additions:
0-15% superpax for white.
4% cobalt oxide for a deep Arabia blue.
1.5% cobalt carbonate and 1% copper carbonate for a bright medium blue.
U1.3% cobalt and 0.8% chrome for deep blue green, vary to adjust shade toward green or blue.
0.2% cobalt oxide and 5% rutile for a light variegated blue.
7% copper carbonate for a vivid metallic green (soluble).
1-3% lithium to variegate and flux to add exciting effects (i.e. with cobalt, copper, iron). One user adds 3% lithium, 1% cobalt carbonate and 0.5% nickel in one variation and 3% lithium, 2% copper carbonate and 1% iron in another.

Pictures

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Hansen 20x5 Clear Cone 6 Base Glaze" id="83886" key="XhZPNGN9" date="2025-04-14" codenum="G1214M" picturebasename=""> <recipelines> <recipeline material="Wollastonite" amount="20.000" tolerance=""/> <recipeline material="Ferro Frit 3134" amount="20.000" tolerance=""/> <recipeline material="EPK" amount="20.000" tolerance=""/> <recipeline material="Silica" amount="20.000" tolerance=""/> <recipeline material="Custer Feldspar" amount="20.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 1997-02-07, Modified: 2025-04-14 19:13:02

Cone 6 Clear Glossy Base

Total:110.10

Auto Unity Formula + Analysis

Notes

The base recipe of the product sold by Plainsman Clays.

There are lots of pages and pictures online about this recipe and stain-added versions (e.g. at digitalfire.com and plainsmanclays.com). The page at Plainsman Clays has mixing and usage information.

This recipe has proven to work very well as a general purpose cone 6 transparent. It works best if ball milled (for lowest possible thermal expansion, best surface quality, least surface defects, best clarity). Unlike many others, this has very high SiO2, that means the best possible durability. It also has significant Al2O3, further contributing to stability of the melt and glass.

Although EP Koalin is used here, we have produced even better results using Grolleg and New Zealand kaolins. Using all three it is possible to get a slurry with excellent suspension and applications properites if attention is paid to the thixotropy.

This fits most Plainsman Clays bodies (and those of other manufacturers). But it does not fit Plainsman P300, a cone 6 whiteware, unless ball milled or a 325mesh silica is used.

Some clay bodies having very low silica content may craze this, in this case consider using the G1214U recipe.

Pictures

URLs

Technical informat..at digitalfire.com

Mixing, adjustment..PlainsmanClays.com

Alternate Code Number:MG6CG

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 6 Clear Glossy Base" id="180072" key="b2opWfcW" date="2024-10-02" codenum="G2926B" picturebasename=""> <recipelines> <recipeline material="Nepheline Syenite" amount="18.300" tolerance=""/> <recipeline material="Ferro Frit 3134" amount="25.400" tolerance=""/> <recipeline material="EPK" amount="19.600" tolerance=""/> <recipeline material="Vansil W-30 Wollastonite" amount="6.900" tolerance=""/> <recipeline material="Silica 325 mesh" lookup="Silica" amount="37.600" tolerance=""/> <recipeline material="Silverline 303 Talc" amount="2.300" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2014-05-15, Modified: 2024-10-02 19:22:40