Our new ultra-clear cone 04 transparent base glazes for 2021

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

See Also:
Replacing Talc with Nepheline Syenite or Dolomite in Cone 04 White Bodies

G1916Q and G3879 and low-expansion versions of each. These are excellent bases and enable expansion-adjustability (by blending).

Cone 05+ Expansion Adjustable Gloss Base

Code #


Materials Amt
Ferro Frit 3195 65.000
Ferro Frit 3110 10.000
Ferro Frit 3249 10.000
No. 5 Ball Clay 15.000


Auto Unity Formula + Analysis

CaO 0.56 8.38%
MgO 0.12 1.25%
K2O 0.01 0.36%
Na2O 0.31 5.24%
(KNaO) 0.33
TiO2 0.01 0.19%
B2O3 0.96 17.87%
Al2O3 0.50 13.75%
SiO2 3.19 51.46%
Fe2O3 0.00 0.12%


Si:Al: 6.3:1
SiB:Al: 8.3:1
R2O:RO: 0.3:0.7






*This recipe provides great thermal expansion adjustability in a low fire clear glaze. It combines a middle-of-the-road thermal expansion frit with a very low and very high expansion frit (they cancel each other out but increase gloss of the otherwise silky Frit 3195). The frits in this recipe are common (the 3249 less so but it deserves to be common because of its utility).

This melts well from cone 05 and is stable to cone 2 or higher.

Do not assume the glaze fits because a piece emerges from the kiln without crazing or shivering. Thermally stress it (by two minute boiling-water and ice-water immersion cycles). We refer to this as the 65:10:10:15 recipe.
If this crazes, try 65:20:15 (3195:3249:EPK).
If it shivers, use 65:20:15 (3195:3110:EPK).

The ball clay also imparts good working properties and it has a lower LOI than EPK (to generate less micro-bubbles in the glaze).

Add 2% iron oxide on terra cotta bodies to enhance the red color of (when used as a transparent) and acts as a fining agent to remove the microbubbles they produce.

Because this employs ball clay, it the glass will have am slightly amber color (from the Fe2O3 in the clay). If that is an issue, try using a kaolin instead (we recommend New Zealand or Grolleg).

Although drop-and-soak firing schedule helps clarity of transparent glazes at higher temperatures this glaze will produce crystal clear results with fast firing.

We found about 3800 water for 4000 water to get 1.44SG. The slurry gels more than with EPK.


G1916Q at Cone 01 on 3D+iron

Very nice results on L3724E red body at cone 01. Piece is very strong.

1916J and Q fired to 1450F

These glazes are starting to melt, the surface having reached the consistency of a porcelain and have densitfied to very low porosity. Notice the iron in the ball clay really shows up at this stage (it will be less evident later).

G1916Q Cone 04 using 04DSSC schedule

Counterclockwise: L212, Raku, Buffstone, L213, L210, L215 Crazing out-of-the-kiln on Raku and buffstone. Bisque 04-03.

G1916Q and J fired 1650-2000F

Ten-gram balls melted and flattened as they fired. They soften over a wide range, starting well below cone 010! At 1650F carbon material is still visible (even though the glaze has lost 2% of its weight to this point), it is likely the source of the micro-bubbles that completely opacify the matrix even at 1950F (cone 04). This is an 85% fritted glaze, yet it still has carbon; think of what a raw glaze might have! Of course, this is a thick layer, so the bubbles are expected. But they still can be an issue on a piece of ware. So to get the most transparent possible result it is wise to fire tests to find the point where the glaze starts to soften (1450F in this case), then soak the kiln just below that (on the way up) to fire away as much of the carbon as possible.

Success with cyrstal clear glaze cone 03

Uses Cone 03 soak-soak-slow cool schedule. Left: P6282 with 3685U slip and 1916Q. Clear and very good. Glaze is thicker than the other two. Shivering on lip, the slip is not fitting the body. Center: P6282 with G2931F Ulexite clear. Better clarity even though it is applied very thin. Shivering on lip, the slip is not fitting the body. Right: L3724F with 3685U slip. No shivering. Very good coverage of the glaze, very clear, the best I have seen yet!

G1916Q on L215, L212, L210, L213, Buffstone at cone 03

All exited from the klin without crazing. The L215, L213, L210 and L212 samples subsequently survived a 300F/Icewater test without crazing, but the Buffstone did not. The L213 would not likely survive a cold-to-hot test without shivering.

1916Q cone 04, 03

Both were slow cooled. While the cone 04 version is glassy and ultra-gloss, it has significant clouding of micro-bubbles. The cone 03 version, right, is completely transparent.

G1916Q on L210 fired at cone 04

G1916Q+2%Iron on L212 talc body fired at cone 05

This will likely shiver over time. But the speckle that happens on white bodies is clearly visible.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 05+ Expansion Adjustable Gloss Base" id="56565" key="Wtf3bGzT" date="2021-09-11" codenum="G1916Q"> <recipelines> <recipeline material="Ferro Frit 3195" amount="65.000" tolerance=""/> <recipeline material="Ferro Frit 3110" amount="10.000" tolerance=""/> <recipeline material="Ferro Frit 3249" amount="10.000" tolerance=""/> <recipeline material="No. 5 Ball Clay" amount="15.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2014-03-04, Modified: 2021-09-11 21:59:03

Cone 05+ Lower Expansion glaze

Code #


Materials Amt
Ferro Frit 3195 60.000
Ferro Frit 3249 25.000
New Zealand kaolin 10.000
45 micron Silica (Silica) 5.000


Auto Unity Formula

CaO 0.51
MgO 0.28
Na2O 0.21
(KNaO) 0.21
B2O3 1.12
Al2O3 0.51
SiO2 3.08


Si:Al: 6.0:1
SiB:Al: 8.2:1
R2O:RO: 0.2:0.8






296.00 per kg


*This is a much-lower-thermal-expansion version of our standard G1916Q low fire clear recipe (which was delay-crazing on the L4410C, L4410K, L4410L cone 04 test bodies). The lower expansion was achieved by eliminating all high-expansion 3110 and more than doubling the low-expansion 3249. This now shivers on our L4170B terra cotta (use the G1916Q for it).

This also switches the ball clay for New Zealand kaolin, producing a much more transparent glass. And this is melting better (since frit 3249 is a very active flux).

The lower surface tension of this make it a better candidate than G3879 for opacification with zircon.

1500g powder, 1200g water produced a specific gravity of 1.49 and yield just over 1.80 litres. Sieving to 80 mesh was required to break down the kaolin agglomerates.



Joe: August 12/21
1500 grams powder
1200 grams water.
Screened 80 mesh. S.G. 1.49
At this S.G. yield is just over 1.80 litres.
Glaze seems a little thick, maximum 5 second vigorous stir time to stettling after allowing to saturate overnight. Glaze falls off spatula very easily so am leaving here for Tony to evaluate. This glaze was difficult to screen at this S.G. but any more water and it might be too thin.

Joe: I am thinking if you want to properly assess glazes with New Zealand Kaolin in them that you have to screen the glazes first. This kaolin does not break down easily and you can see tiny dots of clay on the spatula when you stir glaze even after it is allowed to saturate overnight. Once screened 80 mesh, these agglomerations disappear.


G3879C, G1916Q, G1916QL1 on L213 Cone 04

The move from ball clay to New Zealand kaolin (centre mug vs right mug) greatly improves the clarity (because of the reduction in iron and titanium).

Cone 04 G1916QL1 vs G3879C melt flow comparison

G1916QL1 is more melt fluid so it is likely useful before cone 04. But G3879C is also very fluid (it also has a higher surface tension). Both are producing textbook high quality flows.

Spectrum 705 Black, G1916QL clear on L4410K at cone 03

The quality of this piece is amazing! The evenness of coverage that can be achieved with brush-on glazes is impressive. This was my favourite coffee mug. However it did finally craze after about 2 weeks of use.

G3879C, G1916QL1 on L4410L Bisque 1800 glaze cone 04

No crazing after weeks, ultragloss Frit 524 has much less iron.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 05+ Lower Expansion glaze" id="202545" key="WWrRDMoe" date="2021-09-19" codenum="G1916QL1"> <recipelines> <recipeline material="Ferro Frit 3195" amount="60.000" tolerance=""/> <recipeline material="Ferro Frit 3249" amount="25.000" tolerance=""/> <recipeline material="New Zealand kaolin" amount="10.000" tolerance=""/> <recipeline material="45 micron Silica" lookup="Silica" amount="5.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2014-03-04, Modified: 2021-09-19 19:10:03

Cone 04+ UltraClear Glossy Base

Code #


Materials Amt
Fusion Frit F-524 850.000 82.93%
Fusion Frit F-69 40.000 3.90%
EPK 90.000 8.78%
Silica 45.000 4.39%


Auto Unity Formula

BaO 0.04
CaO 0.44
MgO 0.05
K2O 0.10
Na2O 0.12
(KNaO) 0.21
SrO 0.25
B2O3 0.66
Al2O3 0.47
SiO2 3.91


Si:Al: 8.4:1
SiB:Al: 9.8:1
R2O:RO: 0.2:0.8






3.17 per kg


*I developed this for cone 04 to fit as many clay bodies (without crazing) as possible (my Zero3 clear works well on specific bodies but does not melt enough at cone 04 and its thermal expansion is too high to fit some bodies). The frits in this recipe are less common among potters but common in industry.

I found the inspiration for this on testing many commercial clears and finding one that stood above the others regarding fit and clarity at 04 (I had it analyzed and reverse engineered it using the materials I have). I had it analyzed at a lab and then created a recipe to source the same chemistry. A stroke-of-luck was that a frit we already use to produce another glaze, Fusion Frit F-524, is close to the complete chemistry needed. F-524 is an expensive frit, but you get what you pay for! The glaze is heads-above a number of commercial clear glazes I have tested (they are not ultra clear, they pinhole or blister or craze, they are not glossy enough, their slurries do not permit dipping, they are not adjustable). F-69 is also expensive, but it enables fitting this to any body.

I have been surprised by other aspects of this recipe. It is crystal-clear on any body at any thickness (at cone 04 and above)! Additions of tin and zircon produce a white that melts just as well as the clear. It is amazing how the mobile the melt is, how it runs right off my fluidity checker! Yet it is not significantly more mobile at cone 1 than cone 04 (I glazed lots of pieces up to cone 2, it seems the higher the temperature the better this works!). And it has the amount of SiO2 and Al2O3 that a cone 6 glaze has! There is some kind of magic with this chemistry that I am anxious to learn more about.

While it hardens to a powdery surface, it is amazing how little gum solution is required to make it dry hard and hang on to the bisque when other layers are added on top.

If you want to make bright colored glazes this should be an excellent base (remember, this is the clear glaze recipe currently used by at least one commercial supplier of bright coloured glazes). Encapsulated stains are fantastic at low fire and they can be mixed to fine tune to color. If you are targeting a specific or exotic color then the ability to achieve it will be determined by your ability to source an exotic stain!

For the first mix I added 3000g of powder to 2400g of water to produce a specific gravity of 1.48SG. This produced a watery slurry. I added epsom salts to the point where further additions did not thicken the slurry (up to a total of 7g). This improved it considerably but it was still a little thin (although it covered and applied like a typical dipping glaze, drying in seconds on bisque ware). However the surface was too powdery so I removed 400g of water and replaced it with 400g gum solution. This slowed dip time to about a minute (waiting for the dripping to stop) but it now tolerates thick overlaying of Majolica colors (without them pulling it away from the bisque). For a single-coat dipping (where no overglaze work will be done) I would use about half the amount of gum solution.

I am continuing work on determining how to mix a good slurry of this recipe. It appears it may need to be gelled with VeeGum, that will also harden it and may remove the need for CMC..

This recipe also has implied adjustability (by increasing the low expansion Frit F-69 at the expense of Frit F-524).



Mike ODonnell and Fusion Frits says many customers use F280 and F38. He suggested F5 might be most similar to this. But I found that F524 was by far the closest.


If you want to make this into a air brushing glaze, which actually applies better to the sample board side discs, the glaze must be screened 200 mesh and then specific gravity adjusted to 1.40 and at this S.G. the powder to water ratio would be approx. 54% glaze powder and 46% water content.


Joe: Made some this glaze up in March of 2020 and checked June 2020 ( 3 months later), and glaze has hard panned quite badly, but was able to remix with a little effort. The next day it was easier to remix. The Specific Gravity was adjusted to 1.50 and a moisture content was taken at this point in time and found to be 54.25% glaze powder and 45.75% water content. This glaze was used on the low temperature sample boards for the L215 "bottom" side samples, as well as the L210 "top" side samples. The samples were bisqued in the cone 06-05 range and glaze fired at the same temperature more or less.


Joe: June 4/21
Powder: 3000 grams
Water: 2000 grams
Screened 80 mesh after making and S.G. was 1.59
Glaze seems slightly thick, but falls off spatula surface very easily when tapped against bucket. A vigorous stir of bucket stops in about 4 seconds or so. Leave here to saturate. Yield at these quantities should be 3.14 litres of glaze.


G3879 Clear glaze on Plainsman L211 - Cone 04

Glossy, crystal clear, no crazing! And this is a 42 mesh body containing zero talc.

Melt fluidity comparison with #1 commercial clear

We tested half-a-dozen commercial clears and found G3859 to be the best all-around one. This one has a very similar melt fluidity.

G3879 on Plainsman L210, L215 at cone 04

These are 42 mesh low fire bodies. They normally have issues with pinholing but using this glaze the results are stunning. The L210 contains no talc, the L215 has 10%, yet this glaze does not craze on either one (over time it shivers on the L215).

G3878 has a high surface tension

As can be seen in the way it has melted here.

G3879 on SIAL 25F, Plainsman J2, L4170 TerraCotta

These are very different bodies. The leftmost contains talc to raise the thermal expanison to help prevent crazing with commercial glazes. The center one contains nepheline syenite (for the same purpose). The terra cotta on the right is just Redart and ball clay. This glaze fits are all three! After a year, both the 25F and J2 were difficult to break, very strong!

Sial 10F, 25F with G3879 clear glaze at cone 03

Tile like these were done on a variety of bodies and fired at different temperatures. After a year: Sial 10F Cone 02: No crazing Cone 04: Moderate crazing over time Cone 06: Severe crazing Cone 03: No crazing Sial 25F Cone 1: No crazing Cone 03: No crazing Cone 04: Crazing badly L215 Cone 04: No crazing L210 Cone 04: No crazing L212 Cone 04: Crazing Cone 1: No crazing L213 Cone 04: No crazing

G3879 Clear on L4170 TerraCotta Casting

The clear glaze is G3879. The white on the outside of the one on the left has 10% added zircopax. The overglaze colors are Spectrum Majolica colors.

G3879 with 5% Tin Oxide on SIAL 10F

When mixing Tin (as an opacifer), it is very important to mix it well. The one on the left was mixed poorly (at high speed with my propeller mixer but not for long enough). The one on the right was mixed much better and so produces better opacity. Tin is expensive so this is important. This was not crazed after a year (cone 03).

G3879 on Plainsman Buffstone - cone 03

Buffstone is an entry-level low-price body not intended to fit commercial glazes. Yet this glaze fits at cone 03 (still fitting after a year)! And without any surface defects. At cone 04 it does craze over time.

G3879 Zircon White on SIAL 25F, 10F - cone 03

10% zircopax has been added. It is melting well so the percentage could be increased for great opacity on red burning bodies.

G3879 at cone 1 on SIAL 10F, 25F

Crystal clear, no running. Perfect!

GBMF test on G3879 at cone 1

It is not running and flowing nearly as much as expected. The melt surface tension holds it in place, so it should be able to fire to cone 2 and beyond.

G3879 on terra cotta at cone 04, 02, 1

This is on the L4170 body, it is a lighter firing product, 25F, from SIAL. After use on various bodies, it was clear that fit at cone 03 is better than at 04 and much better than 06.

G1916M, G3879, G2931K on L215 - Thick

Thickly applied encourage poor fit to show up. Clearly, as shivering and cracking demonstrate, G3879 is under excessive compressive on L215. The other two are not showing any issues (other than heavy bubbling because of the thickness). G1216M is a blend of 3124/3124 with kaolin. G2931K is the Zero3 clear.

L213 with G3879 glaze at cone 04

Survived 325F:IceWater test with almost no crazing. However there was a little shivering on the rim after a month. Another mug had no crazing on the inside after several months.

G3879 on L4115J2 buff body at cone 04

Glaze is ultra clear. It was refired at cone 022 to apply a decal. It was 325F to icewater tested without crazing. It was waterlogged (the bottom is bare clay) and then put in a microwave for two minutes. Despite getting incredibly hot it did not fracture or craze! Was still fitting after a year+.

G3879 on SIAL 10F at cone 02

No crazing after several months. Flawless service.


B - Tin White

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 04+ UltraClear Glossy Base" id="154451" key="EqaztWi8" date="2021-09-11" codenum="G3879"> <recipelines> <recipeline material="Fusion Frit F-524" amount="850.000" tolerance=""/> <recipeline material="Fusion Frit F-69" amount="40.000" tolerance=""/> <recipeline material="EPK" amount="90.000" tolerance=""/> <recipeline material="Silica" amount="45.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2019-04-15, Modified: 2021-09-11 21:59:33

Cone 04 UltraClear Low-Expansion

Code #


Materials Amt
Fusion Frit F-524 750.000 73.17%
Fusion Frit F-69 140.000 13.66%
New Zealand kaolin 90.000 8.78%
Silica 45 micron (Silica) 45.000 4.39%


Auto Unity Formula

BaO 0.04
CaO 0.39
MgO 0.18
K2O 0.08
Na2O 0.10
(KNaO) 0.18
SrO 0.22
B2O3 0.75
Al2O3 0.47
SiO2 3.81


Si:Al: 8.1:1
SiB:Al: 9.8:1
R2O:RO: 0.2:0.8






262.63 per kg


*An adjusted version of G3879 to reduce thermal expansion. It switches the silica to 45 micron (325 mesh) for better dissolution in the melt. And it increases the frit low-expansion F-69 (the Fusion equivalent of Ferro 3249) at the expense of F-524.

This also switches to whiter burning kaolin (New Zealand), that improves transparency and removes the amber coloration.

It still fires to the same crystal clear. And is fitting pieces better, especially the L4410L body.

We mixed 1500g powder to 1125g water (57%/43%) to get a specific gravity of 1.54. This produced 1.7 litres.
After allowing to saturate overnight and screening to 80 mesh it worked well.



Joe: August 12/21
Tried the same powder/water ratio as G3879B: 1500/1125 (57%/43%). SG 1.54. 1.7 litres.
Initial glaze was too thin, allowing to saturate overnight thickened it and a vigorous stir settled a 4-5 seconds. Screened 80 mesh,( a lot of material on screen for this amount of powder).
New Zealand Kaolin does not break down easily. Once screened 80 mesh, these agglomerations disappear.


G3879C is firing much whiter, why?

Cone 04. All three clear glazes are on the same body. Left to right: Amaco LG10, G3879C recipe, Crysanthos SG213. The middle one employs Fusion Frit F-524, it is more expensive. But look at the benefit: It fires much more transparent so the piece is much whiter. And it is not crazing or pin holing. And it is glossier.

G3879C, G1916Q, G1916QL1 on L213 Cone 04

The move from ball clay to New Zealand kaolin (centre mug vs right mug) greatly improves the clarity (because of the reduction in iron and titanium).

G3879C vs. G1916QL on L4410K low fire white

The iron from the ball clay is the reason the glaze on the right is off-white.

Cone 04 G1916QL1 vs G3879C melt flow comparison

G1916QL1 is more melt fluid so it is likely useful before cone 04. But G3879C is also very fluid (it also has a higher surface tension). Both are producing textbook high quality flows.

G3879C, G1916QL1 on L4410L Bisque 1800 glaze cone 04

No crazing after weeks, ultragloss Frit 524 has much less iron.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 04 UltraClear Low-Expansion" id="202474" key="Yaw8EZ73" date="2021-09-11" codenum="G3879C"> <recipelines> <recipeline material="Fusion Frit F-524" amount="750.000" tolerance=""/> <recipeline material="Fusion Frit F-69" amount="140.000" tolerance=""/> <recipeline material="New Zealand kaolin" amount="90.000" tolerance=""/> <recipeline material="Silica 45 micron" lookup="Silica" amount="45.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2019-04-15, Modified: 2021-09-11 21:43:29