Substitute For Frit 3195

[Babs]

What is the closest Ferro frit to this frit, and what would I have to add to replace the difference.. I have ample supply of 3124, 3110, trying to convert what they are sold as in Aus, and AUs is 4113.

I'd post the entire recipe but it is from a book,  the authors may not like me posting their recipe...

Is this a time when I should be taking out my formula worksheet and using my own brain. 

Be honest! But kind.

And ok I should be testing.....

[Tyler Miller]

COE of 3124 and 3195 are different (3195's COE is much lower), but they are comparable. The typical 90% frit + 10% kaolin glaze works for both, with 3124 more prone to crazing, and 3195 more prone to shivering.

 

3124 on Digitalfire

 

3195 on Digitalfire

[Babs]

Yes, thanks Tyler I looked at the frits and their composition and noted that if the shivering and crazing occurs to sub a little

% of the other.

I'll make a test run using the 3124  and see what I get.

I'll look again to get the difference in my head.

[Dick White]

Babs, would you feel comfortable posting just a list of the ingredients and amounts of the base, i.e., no colorants, etc., no name, no attribution so we won't know who it came from. I'll punch it through a glaze calc and see what else needs to be adjusted when subbing 3124 or 3110 for the 3195. (Or email it to me, you have my contact.)

[Babs]

Thanks Dick

100.00% High Calcium Semi-Matte #1

20.0% Ferro Frit 3195

29.0% Wollastonite

4.0% Nepheline Syenite

30.0% Kaolin - EPK

17.0% Silica

 

Think you know it:-)

Frit is pretty expensive here , another consideration. just looking for another glaze

[Dick White]

Babs, I think I've seen that one somewhere before. And I might know the guy, been to his house even... He's not so picky about the recipe moving around, it's all over the internet. I'll fiddle with the recipe some to see what I can do with other materials and the frits you have - 3110, 3124, and your Aussie 4113.

[Dick White]

Try this:

Aussie frit 4113 - 9.4%

Frit 3124 - 9.4%

Wollastonite - 26.0%

Neph Sye - 3.3%

Kaolin - 14.9%

Calcined Kaolin - 14.7%
Colemanite - 5.2%
Silica - 17.1%

 

I am making some assumptions completely out of my own head about the availability of these materials Down Under (e.g., the colemanite vs. Gerstley). Let me know if you want me to put something different in the mix.

[Babs]

Thanks Dick, I'll calcine the kaolin nest bisque, other ingredients are fine but will have to more Wollastinite, beats me why the numbers have to be different globally!

Thanks for your time, much appreciated

B

[Dick White]

Babs, here is a completely different take on it, using only natural materials, no frits. I don't know how this will work, haven't tried it, but the chemistry math is the same as the Ron/John's high Ca #1.

 

First note - wollastonite (calcium silicate), which you say you are running low on, is chemically equivalent to whiting (calcium carbonate) with silica thrown in. An issue with whiting is the huge LOI when it breaks down to CaO and CO2, and then the CO2 (which was about 1/3 of the original whiting) goes up the stack. Sometimes it does not make it all the way to the stack, and remains trapped as bubbles in the glaze. Then you switch to wolly to get rid of the gas, but since wolly is half silica, you have to cut the silica elsewhere in the recipe. Or if you are starting with wolly and going the other direction as with this one, sub with whiting and add silica.

 

Second note - this particular glaze has a LOT of calcium, as suggested by the name. Not a problem in itself, but that much calcium needs a fair amount of boron to melt at ^6. A primary source of B in natural materials is Gerstley or colemanite, whichever is more readily available to you Down Under. (The boron came from the 3195 in the original.) I've used Gerstley in this one. Then I added whiting to get the calcium, and neph sye to get the needed alkalies. That leaves us with the alumina/silica to deal with. This particular glaze is on the upper end of the alumina and silica limits, which is why it is so durable and stable. However, getting there is problematic. In the absence of alumina coming from a feldspar flux, which there is very little of in this recipe as it is mostly calcium, leaves you with clay (kaolin in this case) as your source of alumina and silica. But getting that much alumina requires a ton of kaolin, which is going to cause the glaze slurry to shrink and crack as it dries. The solution is to use half and half uncalcined EPK and calcined EPK. Then fill in with however much silica is needed to finish.

 

So, here it is:

EPK - 14.2%

Calcined EPK - 14.3%

Gerstley - 15.8%

Whiting - 17.3%

Neph sye - 7.5%

Silica - 30.9%

 

Have fun with it.

[Babs]

Thank you, I was reading about Wollastonite and its chemical composition, then thought, not being a chemist but did do High School Chem in the early 60's, that as I have a  lot of Talc, that I could go for  a high Mag Matte instead!!!!, putting off calcining Kaolin here...

But when the relies leave I will calcine some as I have another glaze which cracks off the pot as it dries, and it has a bunch of Kaolin in it.

I'll give the above recipe a go as well, as I would happily not pay the price of  the frits. I then unscientifically do another test, simply??? subbing the Talc for the Wollastonite........ whole new set of molecular weights right??And ratios of elements, but maybe I'll discovet THE glaze!!. 

Another question.The rutile I have is a dark colour, I have some light as well, chemically the difference?

Thanks a lot for your info.

Babs

[Dick White]

Light vs. dark rutile (Luke vs. Darth?) - a copy and paste from Tony Hanson's excellent digitalfire reference website -

 

"Rutile is available in light calcined ceramic grade powder (very fine particle size), dark uncalcined powder, and granular form. Either grade of powder can be ground very fine (e.g. 325 mesh). In glazes it is generally better to use the ceramic grade since the decomposition of raw rutile during firing can be a source of glaze imperfections like pinholing and bubbles (even larger amounts of the ceramic grade, e.g. 8%, can also cause problems)."

 

https://digitalfire.com/4sight/material/index.html

 

Regarding the calcined EPK, you can't just take the original amount in the recipe and replace half of it with an equal amount of calcined, as the calcined portion is "more concentrated" (for lack of a better word) than the raw stuff. You can see that in the % by weight table in the Seger spreadsheet I sent you. This is where the glaze calc software comes in handy. It does all the math instantly, you just tweak the quantities up and down until the UMF numbers are back to where you want them.

 

And sure, have at it with the talc. Do some line blends to see what happens.

[Dick White]

One other thing to consider when working with a high Mg glaze - there will be no blue colors. Cobalt and Mg = purple.

[Babs]

yeh, right, hmmm...ponder time here..

[High Bridge Pottery]

I don't agree about LOI and bubbles.

I bought wollastonite and traded out whiting and it made no difference to bubbles. I got rid of everything with high LOI, still bubbles. Personally I would stick with whiting/dolomite as they are much easier to sieve. Wollastonite is a pain in the butt to work with, 20-30min plus to sieve it and I found it to make no difference really.