Cone 6 Glaze with Low Calcium

[HenryBurlingame]

What is the source of boron people are using to get a cone 6 glaze with low calcium? Seems like gerstley borate as well as the common ferro Frits all have calcium…

Edited August 23 by HenryBurlingame

[HenryBurlingame]

OK, so after looking through the analysis of every ferro frit, it looks like ferro frit 3269 could get you boron with a very low amount of calcium. Just in case someone else was interested in this as well.  Cone 6 glazes seem to naturally come with a lot of calcium from the usual ingredients.

Edited August 25 by HenryBurlingame

[Marilyn T]

Cone 6 glaze G3906E from Digitalfire site has 0.24 calcium and uses the following ingredients.  Boron is sourced from FF3110 and FF3249 but totals only 0.11 which is slightly low for a cone 6 glaze however it seems to melt well at cone 6.   How low do you want the calcium to be?   

G3906E

Materials	Amt
silica	32.000
Dolomite	8.000
Bentonite	2.000
EP Kaolin	11.000
Strontium Carbonate	5.000
Ferro Frit 3110	22.000
Ferro Frit 3249	6.000
Zinc Oxide	3.000
Spodumene

[Hulk]

Thanks Henry, I'd looked some, but hadn't found one that didn't also include something I didn't want, e g. the high K2O and Na2O in FF3269, which may be ok for some of my glazes (will check), however, not for the liner glaze, which is very low in those two oxides on purpose, anti-crazing...

How low, good question!

Added:
Looking over my glaze recipes - the ones I use, looks like two could be converted to FF3269, in terms of Na and K (but then the Ca would be low).

Picking frits that have low (less than 5%) calcium* and the "things I didn't want"
CC257              barium, no boron
FB284-M         barium, low boron
3225                   high temperature frit
3249                   "
3269                   that's a maybe, err, high K, Na
3403                    lead, no boron
3482                    lead
5301                    maybe, "high expansion leadless fluorine frit"

Looking at other charts/sources, picking frits with less than 5% calcium*, boron at least 15%
3278                   Ca 6.8%
F38                      high MgO
F69                      also high MgO
F567                   high Na

There may be more.
The high MgO Fusion frits are intriguing, for I use "Texas talc" in a few glazes for the MgO.
I'm not finding the comprehensive chart of all frits; above gleaned from vendor charts/lists, where they list what they have in stock or could maybe get.
    

*There are several more that have between 5-15% calcium, hence "how low" question.

Edited August 26 by Hulk
echo; added; intrigue

[Min]

On 8/23/2024 at 7:48 AM, HenryBurlingame said:

What is the source of boron people are using to get a cone 6 glaze with low calcium? Seems like gerstley borate as well as the common ferro Frits all have calcium…

Just curious, why low calcium requirement?

[HenryBurlingame]

 As low as possible pretty much. So I can use other alkaline earths for the colors they give with the colorants in the glaze. Guess I actually should have said a source of boron with low alkaline earth content, but it was easy to find one with no magnesium, strontium, barium, or zinc :-).

Edited August 26 by HenryBurlingame

[HenryBurlingame]

12 hours ago, Hulk said:

I'd looked some, but hadn't found one that didn't also include something I didn't want, e g. the high K2O and Na2O in FF3269

The 3269 is interesting because you could theoretically make a cone 6 base glaze with only 4 ingredients. The frit (which gives you the boron AND the alkali metals), silica, clay, and your choice of alkaline earth. Glazes would be a bit more expensive though, but not by too much. I'm probably going to order 10lbs or so of the 3269 and play around with it.

Edited August 26 by HenryBurlingame