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RICHARD SE

Clear oxidation glaze

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Hi all

hope you can help

i found this recipe below   I have translated it to this
Have I got it right

K FELDSPA  40-45  %                         POTASSIUM  FELDSPA

Si02.     20 %                                              SILOCON DIOXIDE
CaCo3. 8.  %                                             CALCIUM CARBINATE
Zn0.      6    %.                                            ZINC OXIDE
Sro3      5-8   %.                                       STRONTIUM CARBONATE
A1203.  5-7   %                                     ALUMINA calcined 300#
CLAY    8-10  %                                     Kaolin
 
but has turned out a white instead of clear see picture 


 

8A073FAA-9136-406F-870F-1F03BAB1F66B.jpeg

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It's unusual to see calcined alumina added to a glaze recipe. Alumina is usually supplied mostly by the clay content of the glaze, ie the epk or ball clay. I don't think your glaze is melting enough, probably because of a high alumina level and is appearing white because of being unmelted. Where is the original glaze recipe from and what cone is it meant for?

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4 hours ago, RICHARD SE said:

Hi all

hope you can help

i found this recipe below   I have translated it to this
Have I got it right

K FELDSPA  40-45  %                         POTASSIUM  FELDSPA

Si02.     20 %                                              SILOCON DIOXIDE
CaCo3. 8.  %                                             CALCIUM CARBINATE
Zn0.      6    %.                                            ZINC OXIDE
Sro3      5-8   %.                                       STRONTIUM CARBONATE
A1203.  5-7   %                                     ALUMINA calcined 300#
CLAY    8-10  %                                     Kaolin
 
but has turned out a white instead of clear see picture 


 

8A073FAA-9136-406F-870F-1F03BAB1F66B.jpeg

Generally Alumina is not added to recipes as it’s really hard to distribute throughout in this form. Generally something most avoid. Certainly different.

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Agree it looks underfired just from the picture.  That satiny-matte-like finish with a surface that is not quite smooth looks like other underfired work I have seen.   Also the opaqueish whiteness (as opposed to transparency/clearness) suggests that there are underfired ingredients in the glaze which have not combined in to the melt.

also, eyeballing the ratio of outright silica to alumina in this glaze - before even including the kaolin - already firmly suggests matte glaze to me.  Add in the kaolin and it would be even more matte I think.  Perhaps the stains were meant to add some (a lot?) of additional fluxing power to the base glaze and hence it cannot be used without them? 

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A few thoughts...

- As we don't have the analysis for the Chinese feldspar it could be that it's higher in fluxes and lower in alumina than what you use, this might explain why they added alumina oxide to the recipe.

- There is quite a bit of wiggle room in the glaze recipe, 4 of the 7 ingredients have a range of amounts to add, this leads me to think there is some variance with the materials being used in the original recipe.

- We don't know the claybody that this glaze was intended for, if it's a highly fluxed porcelain that would help the glaze melt. If you are using it on a stoneware it's not going to have the same interface therefore won't be as melted. I don't think this would amount to a huge difference in the fired surface but perhaps contributes to the underfired look of your glaze.

What are you looking for? A clear glaze for ^10 for functional pots? Do you need it to contain the same fluxes? 

  

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Hi Min

thanks for your help

the stains I am using are reds and yellows 

they are not coming out as bright as I would like when I use them in the standard clear I have 

40% feldspar 

30%silaca

20%whiting

10% kaolin 

thanks again Min

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The red and yellow stains, are they cadmium inclusion stains, if not do you know what they contain? If they are cd stains, how fast are you cooling the kiln and have you tried adding 2% zirconium to the base to brighten the glaze? (it's not enough to opacify the glaze but helps cd inclusion stains brighten) With your 4321 base are you getting a smooth melt with no bubbles when using the stains? 

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Since you're firing in oxidation, is there any particular reason you're firing to cone 10 instead of cone 6? You'll get better color response at lower temps. Also, red and yellow inclusion stains do not behave like normal stains. They don't go into melt like typical stains, so you often need more stain to get good color, and they often lack depth in appearance.

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comparing Richard's clear with the cone 10 clear I use regularly.  

The recipe units are in grams

Richard se              ::           mmr    
----------      -----    ::      ----  -----------
feldspar      45       ::       49     feldspar
silica            20        ::        22     silica
CaCO3         8        ::        17     whiting (CaCO3)
zinc oxide   6         : :         2      zinc oxide
SrCO3         8         ::          0    
Alumina      7         ::          0    
kaolin        10         ::        10      kaolin
total        104         ::     100      total 


I would keep the mix you have tested and add whiting in small steps until you get the "clarity" you want,  or/and  lower the alumina amount until get "clarity".  I have removed the zinc and still gotten a good glaze.  The mmr glaze is a base for at least 5 glazes in the studio. It works in both oxidation and reduction.  We get a bright white by adding Zircopax.  I would expect that the alumina would also produce a white. 

LT

Edited by Magnolia Mud Research
for grammer

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7 hours ago, Min said:

The red and yellow stains, are they cadmium inclusion stains, if not do you know what they contain? If they are cd stains, how fast are you cooling the kiln and have you tried adding 2% zirconium to the base to brighten the glaze? (it's not enough to opacify the glaze but helps cd inclusion stains brighten) With your 4321 base are you getting a smooth melt with no bubbles when using the stains? 


I will try and find out about cadmium 

12 hour cooling 

I have not tried Zirconium 
see samples I tested  top row in white 4/3/2/1/ base and bottom row in 4/3/2/1/ clear base1F03D3C2-B924-471A-BD62-BF5BAC3F9E8A.jpeg.806ea3af44cdffa45bb866eb1733faac.jpeg

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Those do look like encapsulated zirconium-cadmium-selenium inclusion stains and I see what you mean about your tests looking flat. I would double check they are rated to go to cone 10 even though most are. I think it's going to take adjusting to a more fluid base or alternatively using the stains in an underglaze (or slip/engobe) then putting a clear glaze overtop. I wouldn't add any more spar, it's my understanding that you want to keep the alkali metals low when using these type of stains (wouldn't add lithium either for that reason). 

How does the Leach 4321 work for you without the stains? Are you getting a nice gloss? What's the white glaze base opacified with?

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Hi Min

yes I’m quite sure they are up to 1300 Celsius 
4321 works very well with anything else I have tried ,well at least as far as I know anyway 

10% zircosil added  for white base 

thanks again Min

regards richard 

 

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4 hours ago, RICHARD SE said:

Hi Min

yes I’m quite sure they are up to 1300 Celsius 
4321 works very well with anything else I have tried ,well at least as far as I know anyway 

10% zircosil added  for white base 

thanks again Min

regards richard 

 

Just a quick add here

4321 has been a time tested glaze with a durable flux ratio for many years. Easy to remember also

version with neph sy has a Slightly more durable flux ratio near 0.3::0.7

  1. neph sy 40
  2. Silica 30
  3. whiting 20
  4. Epk 10

 

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7 hours ago, Bill Kielb said:

also

version with neph sy has a Slightly more durable flux ratio near 0.3::0.7

  1. neph sy 40
  2. Silica 30
  3. whiting 20
  4. Epk 10

Except with Nepheline Syenite the KNaO bumps up from 0.23 with Custer feldspar to 0.29 with Nepheline Syenite (using Insight) and Cd inclusion stains do better without too high a level of alkali metals. Agreed the Leach 4321 is a time tested glaze, I just wanted to confirm that Richard is getting a good melt with it using his ingredients, kiln and firing profile. I do think Neil brings up a really good point about ^6 versus ^10, is this an option for you?

Edited by Min
added a thought

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1 hour ago, Min said:

Except with Nepheline Syenite the KNaO bumps up from 0.23 with Custer feldspar to 0.29 with Nepheline Syenite (using Insight) and Cd inclusion stains do better without too high a level of alkali metals. Agreed the Leach 4321 is a time tested glaze, I just wanted to confirm that Richard is getting a good melt with it using his ingredients, kiln and firing profile.

Yeah, at this point I am lost in this conversation. What started as a recipe adding alumina confused me the most. I mentioned the neph sy because it gets this recipe to a gloss ratio of about 8:1 vs a not so glossy with let’s say Custer at about 10.5:1. His fired results appear more matte than gloss so maybe a bit dull. His white base actually looks bright though.

As far as moving from .23 ish to .29 ish, not sure this is materially different. The Inclusion (encapsulated )  stains should be inert so not sure a minor change will hurt. The color effect is definitely derived from the refraction angle though so I think we are agreeing somewhat.

So thinking about this now:
I would definitely clear this up and get it to a gloss which means trying the neph sy which may or may not affect the color  with the small change in RO (as you mentioned) but also has a good chance to improve the gloss and clarity which might get him the brighter look he seeks.

In the end something to try I think, but agree 100% good melt etc..... is wise.

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11 hours ago, Bill Kielb said:

The Inclusion (encapsulated )  stains should be inert so not sure a minor change will hurt.

In theory but not in practice. Examples would include a chrome green stain in a zinc glaze equals brown, chrome tin red or pink in a low calcium glaze equals loss of red/pink colour, alumina pink causing refractory effect in glaze etc. Host glaze needs to be compatible with the stain composition. 

18 hours ago, RICHARD SE said:

10% zircosil added  for white base

Okay, this is good info, it confirms that the addition of some zirconium is helping clear the bubbles/pinholes that are seen in your tests without it. For a clear try just 2% zircosil plus and minus 0.50% 

I would attack this problem from a few angles, well melting gloss base plus some zircosil, Bill's suggestion of using  Nepheline Syenite (with and without zircosil) in place of a potash spar, a cone 6 gloss if ^6 is an option for you (again with a titch of zircosil). I would also try adding another flux to your 4321, perhaps some strontium, if your glaze will tolerate more whiting without developing crazing then you could try bump that up, same for the original glaze you posted as @Magnolia Mud Research suggested. Keep fast cooling the kiln (don't do a slow cool down).

edit: forgot to add that I wouldn't use barium as a flux, apart from issues inherent with barium it can also impede the colour development of these stains.

Edited by Min
added a thought

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On 12/25/2019 at 5:22 AM, neilestrick said:

Since you're firing in oxidation, is there any particular reason you're firing to cone 10 instead of cone 6? You'll get better color response at lower temps. Also, red and yellow inclusion stains do not behave like normal stains. They don't go into melt like typical stains, so you often need more stain to get good color, and they often lack depth in appearance.

Hi Neil 

 

I did not know they would work at cone 6. 
The 4/3/2/1/ recipe will work at cone 6 I take it

I can try this and add more stain 

I have added 10% normally but a test I did last week I added 15 % and the colour did come up stronger 

The stains I was told were firing temperature of 1300    I thought that was the temperature they needed to go to So  1300 is anything up to ? Ok thats good 

I am inexperienced at this game   Started this year. Bought my first kiln about 6 months ago 3.3 cubic ft.  That’s why I’m looking to get a bigger kiln as I have nearly out grown it

Been a real challenge but an awful lot of fun with the firing side of things a much bigger challenge 

Throwing pots etc got nothing on getting the firing part right 

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2 hours ago, Min said:

In theory but not in practice. Examples would include a chrome green stain in a zinc glaze equals brown, chrome tin red or pink in a low calcium glaze equals loss of red/pink colour, alumina pink causing refractory effect in glaze etc. Host glaze needs to be compatible with the stain composition. 

Okay, this is good info, it confirms that the addition of some zirconium is helping clear the bubbles/pinholes that are seen in your tests without it. For a clear try just 2% zircosil plus and minus 0.50% 

I would attack this problem from a few angles, well melting gloss base plus some zircosil, Bill's suggestion of using  Nepheline Syenite (with and without zircosil) in place of a potash spar, a cone 6 gloss if ^6 is an option for you (again with a titch of zircosil). I would also try adding another flux to your 4321, perhaps some strontium, if your glaze will tolerate more whiting without developing crazing then you could try bump that up, same for the original glaze you posted as @Magnolia Mud Research suggested. Keep fast cooling the kiln (don't do a slow cool down).

edit: forgot to add that I wouldn't use barium as a flux, apart from issues inherent with barium it can also impede the colour development of these stains.

Hi all    Thanks for all your help

So much information from such experts

to someone with no expertise 

Will try these options and see what happens. The less zircosil and the cone 6 idea. Both sound like worth a try

Will have to make some more test tiles first and will let you know 

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3 hours ago, Min said:

n theory but not in practice. Examples would include a chrome green stain in a zinc glaze equals brown, chrome tin red or pink in a low calcium glaze equals loss of red/pink colour, alumina pink causing refractory effect in glaze etc. Host glaze needs to be compatible with the stain composition.

Not disagreeing but low is relative so I would be careful with considering that practice  as opposed to a general guideline. Chrome oxide and zinc and chrome oxide and  tin are a different subject.

 A practical example for me would be of the hundreds of things that we decorate with encapsulated stains most retain their color pretty accurately with a zinc free clear glaze. Some clear glazes influence some colors more than others because of composition so trial and verification is always the in practice part. Clarity on the other hand always influences the perceived brightness.  I am not at all certain  0.23 would be considered low as opposed to 0.29 

I agree  that the general knowledge is fluxes affect color and variations in fluxes can have an effect but that is the theory. The in practice part is to test and determine how much and at what point for a color or set of colors becomes unacceptable. When someone says low to me it has little  specific meaning. What is low and what is high?

I would test with the neph sy if clear gloss or at least gloss is the goal. Easy to try with various stains and colors actually. . I think you  could get a representative idea by painting the stains on a color pallet, bisque fire, and glaze  them with several clears leaving a section of them unglazed just to see all the potential changes involved and which look is preferred. 
 
So in the end compatibility or suitability would be a function of the tested or fired result. Speculating on the outcome over a few tenths is speculation, testing to see the magnitude change if any,  would be the in practice part to me. 

Edited by Bill Kielb

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56 minutes ago, RICHARD SE said:

I did not know they would work at cone 6. 
The 4/3/2/1/ recipe will work at cone 6 I take it

In general, 4321 is a cone ten glaze and may not melt well at cone six. There are many cone six clear glazes out there. What are you looking for ? Gloss/ matte/ semi gloss/ satin?

We routinely use a high gloss cone six clear as a base glaze and then along with various amounts of stain it provides a celadon or solid look that can be dialed in with respect to color. 

The clear high gloss version in the picture below is used over the painted design and then also used with 2% concentration of the same stain for the bottom of the votive To produce a color matching celadon over  the chatter.

since my wife is a skilled brush artist, she prefers to paint with stains so that what she paints and accents color wise, is pretty much what she gets. Of course testing in advance is always necessary just to be sure the glaze does not significantly affect the color. This clear has an RO of 0.22 btw and does not appear to affect her colors significantly.

31B67BB9-DBCC-4556-91D3-B4FB2A882B84.jpeg.9009c1dece0a4002bb42505eaefcecf1.jpeg

Edited by Bill Kielb

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@RICHARD SE, if you are going to try a cone 6 clear then make sure the clay you use is a midrange clay if you plan on making functional pots. If you use a cone 10 clay at cone 6 then in all likelihood the pots will leak and the glaze(s) will craze over time. Firing to cone 6 will save a lot of wear and tear on both your elements and your kiln versus firing to cone 10.

I'm sorry if we did an information overload on you, it's difficult to get a read with new members regarding their experience / knowledge levels. 

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4 hours ago, Min said:

In theory but not in practice. Examples would include a chrome green stain in a zinc glaze equals brown, chrome tin red or pink in a low calcium glaze equals loss of red/pink colour, alumina pink causing refractory effect in glaze etc. Host glaze needs to be compatible with the stain composition. 

Okay, this is good info, it confirms that the addition of some zirconium is helping clear the bubbles/pinholes that are seen in your tests without it. For a clear try just 2% zircosil plus and minus 0.50% 

I would attack this problem from a few angles, well melting gloss base plus some zircosil, Bill's suggestion of using  Nepheline Syenite (with and without zircosil) in place of a potash spar, a cone 6 gloss if ^6 is an option for you (again with a titch of zircosil). I would also try adding another flux to your 4321, perhaps some strontium, if your glaze will tolerate more whiting without developing crazing then you could try bump that up, same for the original glaze you posted as @Magnolia Mud Research suggested. Keep fast cooling the kiln (don't do a slow cool down).

edit: forgot to add that I wouldn't use barium as a flux, apart from issues inherent with barium it can also impede the colour development of these stains.

Hi all    Thanks for all your help

So much information from such experts

to someone with no expertise 

Will try these options and see what happens. The less zircosil and the cone 6 idea. Both sound like worth a try

Will have to make some more test tiles first and will let you know 

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