Does Frit 3124 bubbles?

[Didiho]

Hi all,

I’m based in Hong Kong and had been testing two glazes with ferro frit 3124, both of them bubbles a lot……. I wasn’t so sure this problem come from 3124, but this time my variant materials are only nephine syenite and 3124, while other glazes with NS doesn’t bubble.

 

I’m not sure if it is the supply contaminated or my firing schedule went wrong. I’ve changed my firing schedule to have a hold section at around 900 degree as I was trying to let the bubbles produced by  boron out. The last glaze improved but the bubbles still appear occasionally. Also there is another hold section of 20mins after the highest temp of firing. My kilns doesn’t do slow cooling schedules.

 

So, I would like to see if there is any recommendations from this community. What should I do? Any substitutes for 3124? (GB is not available in my region, how about 3134?)

Your comment would help a lot!!

Thank you!

Didi

[Chilly]

Hi @Didiho  Welcome to the forum.

When you say it "bubbles", do you mean there are bubbles in the wet glaze?  Or on the pot before firing?  On on the fired piece?

[Bill Kielb]

5 hours ago, Didiho said:

I’ve changed my firing schedule to have a hold section at around 900 degree as I was trying to let the bubbles produced by  boron out. The last glaze improved but the bubbles still appear occasionally. Also there is another hold section of 20mins after the highest temp of firing.

It sounds like bubbles might be pin holes and also sounds like you do not fire by cone so maybe post a Picture of the bubbles, your firing schedule and the glaze recipe you are using. Peak holds can be problematic. Composition can also establish just how much boron you are using which will be relevant to where this is expected to melt and of course pictures will show if bubbles are pinholes.

The frit should be less problematic than Gb so if this recipe is originally Gb please post the original as well.

[Didiho]

8 hours ago, Chilly said:

Hi @Didiho  Welcome to the forum.

When you say it "bubbles", do you mean there are bubbles in the wet glaze?  Or on the pot before firing?  On on the fired piece?

Hi Chilly,

They are bubbles of the fired pieces.

[Didiho]

7 hours ago, Bill Kielb said:

It sounds like bubbles might be pin holes and also sounds like you do not fire by cone so maybe post a Picture of the bubbles, your firing schedule and the glaze recipe you are using. Peak holds can be problematic. Composition can also establish just how much boron you are using which will be relevant to where this is expected to melt and of course pictures will show if bubbles are pinholes.

The frit should be less problematic than Gb so if this recipe is originally Gb please post the original as well.

Hi Bill, 

They are not pinholes but bubbles shown in the picture.. and it is true that i do ramp hold firing.

I was working on Katz-burke matte:

Kaolin    29.23

Frit 3124    22.56

Nepheline Syenite    20.37

Whiting    17.10

Silica    10.74

 

My firing schedule was:

100c/h to 300c

120c/h to 950 - hold 20 mins

130c/h to 1235 - hold 20 mins

 

I had done two glazes containing 3124 and both of them were fired with these kind of huge bubbles. Other glazes that are without 3124 fired with the same firing schedule didn't bubble.

 

Thank you so much for helping!!!

[Roberta12]

@Didiho what clay are you using?  I recently had a clay body do that very thing and had to reduce the firing temperature.

Roberta

[neilestrick]

Frit 3124 itself is not prone to bubbling, so it's all a matter of how it works in the recipe. It's not a great recipe. Calcium is really high, silica is low, so getting into the range of a fake ash glaze, which are prone to bubbling if they're not just right. If you're not going for that rivulet ash glaze look then increase the silica and it should smooth out.

[Min]

A few thoughts about what could be going on with this glaze. Two of the main ingredients, the 3124 frit and the nepheline syenite both begin melting at low temperatures. What this means is any gasses that didn't get fired out during the bisque can get trapped when the glaze starts to melt which seals off the surface of the claybody not allowing any remaining gasses to escape. When the gasses can't escape through the glaze surface they can cause the blisters/bubbles like you are experiencing. Do you vent the kiln well during bisque firing? What's your bisque schedule?

Second thought is you might be firing way too hot. 130C / hr / 1235C peak plus a 20 minute soak could very well be putting you in the cone 7 - 71/2 range. Are you using cones to verify what the kiln is actually getting to? Overfiring can also cause blisters/bubbles.

Third thought after looking at the glaze recipe is there is a lot of raw kaolin and also whiting in the recipe. That much raw kaolin (epk) could very well lead to a crawling glaze. Also, if you have access to wollastonite I would supply the calcium from that instead of the whiting. This will reduce off gassing and the glaze will also melt better. I redid it, using part calcined kaolin and wollastonite below if you are interested.

Being in Taiwan we don't know the chemistry of your materials but this should get you in the ballpark for this high alumina matte. 

 

 

 

 

[Bill Kielb]

On 8/26/2021 at 10:32 AM, Didiho said:

My firing schedule was:

100c/h to 300c

120c/h to 950 - hold 20 mins

130c/h to 1235 - hold 20 mins

I have fired that matte with good result actually. I would definitely make your last segment of the firing match the Orton cone chart which means 60 c per hour in the last 100 c of the firing. So cone 6 = 1222 (from the middle column) and 1222-100 = 1122 so …… 60c per hour starting at 1122 and shut off at 1222. Presently we really don’t know how fast your kiln can go at top temperature and even if it’s 130c you likely are reaching cone 7.  So that I would suggest to fix first and use witness cones in the future. I would see if that helps, but beyond that having used this glaze with lots of folks on Glazy using this glaze, maybe the 3124 is suspect. I see versions of this recipe listed  and tested for cone 6-8 . All the above reasons presented throughout the thread  seem reasonable but I would also check if  that is 3124.

I have seen similar odd results when 3124 / 3134 were errantly mixed up..

[Didiho]

Thanks all,

I’m a bit touched by how helpful you are!!

true that I don’t often use cones in firing, will definitely purchase them after this long way failing

I’m going to do the below tests:

- adding silica in 3 scales

-using the wollastonite recipe

-lowering portion of kaolin

-do 60c/h starting from 1122c

 

will reach you guys back again after they are fired!thank a lot :):)

[Bill Kielb]

5 hours ago, Didiho said:

adding silica in 3 scales

Since I have used this exact recipe and it appears many others have as well with great success just judging by the number of colorant variations posted:

(1) The recipe mix-  If accidentally something was mixed or some quantity was added in error. I would remix and be very sure I had it correct. This has happened to many over time so maybe make a nice precise 100 g  test just to be sure before heading out to reengineer something that seems to have proven very successful for many.

(2) Last thought: Adding silica to this recipe should simply make it go from matte to gloss as the SI:Al rises towards 7:1 and beyond. It is a typical test for a true matte recipe. This recipe is a true matte and requires no slow cooling to be a matte.

[PeterH]

1 hour ago, thiamant said:

In my humble opinion, using Wollastonite instead of whiting wont be of any help at all. By the time your glaze starts to melt all the gas from calcium carbonate is more than gone.

From https://digitalfire.com/oxide/loi

To my untutored eye this supports  both your point, and Bill's comment about the dangers of confusion between 3124 / 3134.

Norm Stuart in https://cone6pots.ning.com/forum/topics/ferro-frit-3124-verses-3134
Ferro Frit 3124 has alumina and melts at ^05, while 3134 has no alumina but more borax and calcium flux so melts at a much lower temperature of ^015.

[PeterH]

On 8/26/2021 at 9:05 PM, Min said:

A few thoughts about what could be going on with this glaze. Two of the main ingredients, the 3124 frit and the nepheline syenite both begin melting at low temperatures. What this means is any gasses that didn't get fired out during the bisque can get trapped when the glaze starts to melt which seals off the surface of the claybody not allowing any remaining gasses to escape. When the gasses can't escape through the glaze surface they can cause the blisters/bubbles like you are experiencing. Do you vent the kiln well during bisque firing? What's your bisque schedule?

Min, would giving a test-piece two bisques before the glaze firing provide a minimally disruptive test of this hypothesis?

[Min]

On 8/28/2021 at 5:45 AM, thiamant said:

In my humble opinion, using Wollastonite instead of whiting wont be of any help at all. By the time your glaze starts to melt all the gas from calcium carbonate is more than gone.

Think of wollastonite as natures frit of silica and calcium which can be taken into the melt easier than a chemically equivalent mixture of silica and calcium carbonate and has a far lower LOI. Boron frits such as Ferro 3124 are starting to melt by 760C. Calcium carbonate decomposes between 750C - 1000C, so the frit is definitely going to be melting prior to the calcium carbonate being finished off gassing. Since it has one of the highest loss on ignition of all the materials we use it just makes sense to supply the calcium from wollastonite rather than calcium carbonate when there is a significant amount of calcium required for the recipe as is the case with this glaze recipe.

10 hours ago, PeterH said:

Min, would giving a test-piece two bisques before the glaze firing provide a minimally disruptive test of this hypothesis?

Perhaps, kind of impossible to know for sure though, especially since we don't know how "dirty" the op's claybody is. When people have just re bisque fired dark bodies with a typical schedule to clean out more of the problem inorganics, organics and sulphur it isn't necessarily successful. It takes slowing down between 700 - 900C range to allow time for the inorganic carbons to burn out.

[thiamant]

9 hours ago, Min said:

Think of wollastonite as natures frit of silica and calcium which can be taken into the melt easier than a chemically equivalent mixture of silica and calcium carbonate and has a far lower LOI. Boron frits such as Ferro 3124 are starting to melt by 760C. Calcium carbonate decomposes between 750C - 1000C, so the frit is definitely going to be melting prior to the calcium carbonate being finished off gassing. Since it has one of the highest loss on ignition of all the materials we use it just makes sense to supply the calcium from wollastonite rather than calcium carbonate when there is a significant amount of calcium required for the recipe as is the case with this glaze recipe.

I think a single material melting range is not as relevant as the whole glaze melting stage, which only happens in the last 100 C of firing. I have fired the same glazes using wollastonite and whiting, and the result is exactly the same. 

[Min]

8 hours ago, thiamant said:

I think a single material melting range is not as relevant as the whole glaze melting stage, which only happens in the last 100 C of firing. I have fired the same glazes using wollastonite and whiting, and the result is exactly the same. 

The op is using approx 22% of a boron frit. Boron frits melt early. From your posts on this forum I believe you are firing to cone 10 and your glazes do not contain boron.  Cone 10 glazes contain materials that get taken into the melt later in the firing than lowfire or midfire glazes. If you have ever had the misfortune of having to stop a firing part way through because of a power or kiln issue and open the kiln you will probably see partially fused glazes well below the firing peak temperature, particularly with fritted boron glazes.

Melt fluidity article here that starts getting into this. How glazes melt article here that goes through the glaze melt process. There is also the article discussing the importance of looking at LOI from Peter's chart above with which he included a link.

 

 

 

 

[Bill Kielb]

44 minutes ago, Min said:

Melt fluidity article here that starts getting into this. How glazes melt article here that goes through the glaze melt process. There is also the article discussing the importance of looking at LOI from Peter's chart above with which he included a link.

 

While wollastonite is likely a better option, many glazes seem to work sufficiently well with calcium carbonate. This one in particular seems to have a wide variety of color tests posted which may indicate the off gassing from CaCO3 is not usually problematic for this recipe. 22% of this recipe is boron Fritt, which means over three quarters is something other than. Or  over 50% of the recipe excluding CaCO3 is something other. I think the off gas issue is a valid argument and  might come into play, but for glazes that have a reasonably successful record maybe initially be sure it  was mixed right, correct materials, correct firing.

[Min]

Had a look at some of those test tiles from Glazy using this recipe. I'm seeing pinholes in the red clay one for sure and smaller pinholes and semi healed pinholes in others, couple examples below. Pins on the red clay could also be from offgassing of the body. Agreed that mixing the recipe with the appropriate frit is important.

 

[Min]

@thiamant, I started a new thread concerning pinholes using your last post as the lead. This thread has evolved into one concerning pinholes rather than the op's original issue. New thread here. https://community.ceramicartsdaily.org/topic/26118-glaze-pinhole-causes-and-remedies/