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Cone 6 Black

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Anyone have a ^6 black recipe that is reliable in that kiln-to-kiln way? I've tried a couple off the net, including one that had Ron Roy's name on it, and they were less than acceptable.

Would anyone care to share a nice glossy black in trade for my humble appreciation?

 

Joel.

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Can you please post a picture of "less than acceptable"?

People have very different ideas of "acceptable", including me :) 

I'v got really nice black surface out of thin coat (and undrefired to cone 6/7, needs >9) black oil spot glaze.

BTW; did you try clear glaze + black stain for start? You can mix a tiny cup-full and test it out. I have seen people swear by Mason Stain 6600 Best Black (Cr Fe Co Ni)

It's sold in US so I have not tested this personally, so I have no idea will this actually work.

 

Cheers!

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The glossy black in Mastering ^6 Glazes is great, called Licorice.  Very deep black, non runny, good with other colors over it. wide firing range.  Base is good with other colorants.

All my recipes are in the studio and I am not.  class there all day, if no one has posted it by afternoon, I will have it in hand and will post it then.

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This is a  from the Van Gilder book. I don't know if it is from te Rob Roy or not, but I have used it with nice effect with other glazes that are posted at his web site. the second and third set of numbers are for 5000 and 7500 grams-this from my glaze compendium spread sheet.

 

Black Licorice       Compound Empirical 50 75 Custer spar 22 1100 1650 Frit 3134 26 1300 1950 whiting 4 200 300 EPK-Kaolin 17 850 1275 Talc 5 250 375 Silica-Flint 26 1300 1950 Total in grams 100 5000 7500         Cobalt carb 1 50 75 red iron oxide 9 450 675 bentonite 2 100 150                         Van Gilder      

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Anyone have a ^6 black recipe that is reliable in that kiln-to-kiln way? I've tried a couple off the net, including one that had Ron Roy's name on it, and they were less than acceptable.

 

Would anyone care to share a nice glossy black in trade for my humble appreciation?

 

Joel.

 

Can you relate what the problem was with the Ron Roy recipe? I've had great results with that one... it's especially nice when overlaid with other glazes.

 

It needs to be applied evenly and a bit on the thick side, though. If it's too thin, it's uglier than the proverbial turd in the punch bowl.

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thank you kohaku,  i describe the awful color i get differently, but the idea is the same.  i must be using it too thin because it looks like the end of the black licorice stick once you have bitten it.  a kind of darkish, brownish ishiness that is not black.  i will try again.  

 

would also welcome any other black glaze suggestions.

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thank you kohaku,  i describe the awful color i get differently, but the idea is the same.  i must be using it too thin because it looks like the end of the black licorice stick once you have bitten it.  a kind of darkish, brownish ishiness that is not black.  i will try again.  

 

would also welcome any other black glaze suggestions.

 

Yup- sounds like it was applied too thin. It's very unforgiving of unevenness as well.

 

It's really a lovely glaze, though- I'd encourage you to experiment.

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thank you kohaku,  i describe the awful color i get differently, but the idea is the same.  i must be using it too thin because it looks like the end of the black licorice stick once you have bitten it.  a kind of darkish, brownish ishiness that is not black.  i will try again.  

 

would also welcome any other black glaze suggestions.

 

Yup- sounds like it was applied too thin. It's very unforgiving of unevenness as well.

 

It's really a lovely glaze, though- I'd encourage you to experiment.

 

 

Any glaze that has 9 RIO and 2 cobalt carb to achieve black is going to look better if you use high purity colorants or increase the RIO if you are using Spanish RIO. If you are getting a brown cast to the glaze then I would suspect weak cobalt. Synthetic RIO is 95% Fe2O3, Spanish is approx 87% Fe2O3, that is enough of a difference to effect the blackness of the glaze. Perhaps by applying the glaze thickly you are achieving the same result as if more iron/cobalt was in the recipe? Slow cooling the kiln might produce a slight off colour also.(think what happens with slow cooled iron reds)

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This gives a slightly metallic looking waxy black glaze

 

Glaze Composition Ingredient Parts

Ball clay                  25
Manganese dioxide 21.5
Talc                         17
Rutile                       11
Red iron oxide         10
Frit 3134                   7
Silica                         6
Copper carbonate     2.7

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Guest JBaymore

This glaze comes up well short in both alumina and silica for cone 6 firing.  Low alumina is .29 and can go as high as .64.  Silica low limit is .24 and can go as high as 4.7. 

 

With the high molecular equivalents of the three metallic colorant oxides shown..... and particularly the very high manganese (is that number you listed correct?)....... I'd guess it will leach. The mettalic surface is likely a result of the precipitation of microcrystaline MgO based structures onto the surface during the cooling cycle...... as coloring oxides and some MgO/SiO2/Al2O3 comes out of the solution melt.

 

OM #4 Ball Clay.............    25.00 
Talc........................    17.00 
Ferro Frit 3134.............     7.00 
Silica......................     6.00 
Iron Oxide Red..............    10.00 
copper carbonate............     2.70 
Manganese Dioxide...........    21.50 
                              =========
                                  89.20

          CaO       0.06*    
          MgO       0.32*   
          K2O       0.01*    
          Na2O      0.03*   
          TiO2      0.01     
          Al2O3     0.16    
          B2O3      0.05     
          SiO2      1.32    
          Fe2O3     0.14    
          MnO2      0.58*   
                      
               
                       Si:Al:    8.23
                      SiB:Al:    8.57
           Thermal Expansion:    7.16
              Formula Weight:  192.48

 

 

best,

 

.......john
 

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This glaze comes up well short in both alumina and silica for cone 6 firing.  Low alumina is .29 and can go as high as .64.  Silica low limit is .24 and can go as high as 4.7. 

 

With the high molecular equivalents of the three metallic colorant oxides shown..... and particularly the very high manganese (is that number you listed correct?)....... I'd guess it will leach. The mettalic surface is likely a result of the precipitation of microcrystaline MgO based structures onto the surface during the cooling cycle...... as coloring oxides and some MgO/SiO2/Al2O3 comes out of the solution melt.

 

OM #4 Ball Clay.............    25.00 

Talc........................    17.00 

Ferro Frit 3134.............     7.00 

Silica......................     6.00 

Iron Oxide Red..............    10.00 

copper carbonate............     2.70 

Manganese Dioxide...........    21.50 

                              =========

                                  89.20

 

          CaO       0.06*    

          MgO       0.32*   

          K2O       0.01*    

          Na2O      0.03*   

          TiO2      0.01     

          Al2O3     0.16    

          B2O3      0.05     

          SiO2      1.32    

          Fe2O3     0.14    

          MnO2      0.58*   

                      

               

                       Si:Al:    8.23

                      SiB:Al:    8.57

           Thermal Expansion:    7.16

              Formula Weight:  192.48

 

 

best,

 

.......john

 

 

Any concern about the high percentage of manganese dioxide? 

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This glaze comes up well short in both alumina and silica for cone 6 firing.  Low alumina is .29 and can go as high as .64.  Silica low limit is .24 and can go as high as 4.7.

 

yeah... but it works, I never ment for it to be used in dinnerware.

 

Also what are your numbers I get somthing entirly different

Oxide   Wt%    Mol%  Unity

Li2O    .00     .00   .00

Na2O    .82    1.17   .30

K2O     .14     .13   .03

MgO     .06     .12   .03

CaO    1.56    2.48   .63

SrO     .00     .00   .00

BaO     .00     .00   .00

ZnO     .00     .00   .00

PbO     .00     .00   .00

Al2O   4.00    3.49   .89

B2O3   1.74    2.20   .56

Fe2O3 35.02   19.49  4.99

SiO2  21.55   31.85  8.16

TiO2  35.11   39.06 10.01

P2O4    .00     .00   .00

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This glaze comes up well short in both alumina and silica for cone 6 firing.  Low alumina is .29 and can go as high as .64.  Silica low limit is .24 and can go as high as 4.7.

 

yeah... but it works, I never ment for it to be used in dinnerware.

 

Also what are your numbers I get somthing entirly different

Oxide   Wt%    Mol%  Unity

Li2O    .00     .00   .00

Na2O    .82    1.17   .30

K2O     .14     .13   .03

MgO     .06     .12   .03

CaO    1.56    2.48   .63

SrO     .00     .00   .00

BaO     .00     .00   .00

ZnO     .00     .00   .00

PbO     .00     .00   .00

Al2O   4.00    3.49   .89

B2O3   1.74    2.20   .56

Fe2O3 35.02   19.49  4.99

SiO2  21.55   31.85  8.16

TiO2  35.11   39.06 10.01

P2O4    .00     .00   .00

 

 

Using Insight my number are nearly identical to John's. Silica being 1.32 and Alumina being 0.15 Which glaze calc program do you use?

 

CaO 0.10* 2.69 3.49

MgO 0.28* 5.21 9.43

K2O 0.01* 0.24 0.19

Na2O 0.03* 0.88 1.04

TiO2 0.30 11.12 10.16

Al2O3 0.15 7.10 5.08

B2O3 0.05 1.73 1.82

SiO2 1.32 36.35 44.13

Fe2O3 0.16 11.53 5.26

MnO2 0.58* 23.03 19.34

ZrO2 0.00 0.12 0.07

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Guest JBaymore

I'm using Insight and the Level II online North American database with many of the materials then adjusted to my local materials supplier typical analysis.  Since this is to be electric fired, I kept the RIO in the ampoteric oxide form.... but MnO is a flux in both oxidation and reduction... so that is set to go into the flux unity.  You are correct...... I made the mistake of simply omiting the small amount of CuO in the flux unity... so if included that will drop the other flux numbers just a tiny bit.

 

Yes... the manganese at that percentage level is of GREAT concern in this particular case... and will account for a huge proportion of the surface microcrystaline materials.

 

An important point I make in my materials classes is that it is always possiblke that while the person who has the original recipe knows enough not to put certain formulations onto food contact (or even POTENTIAL food contact) surfaces... the people that get the information shared to them (via workshops, books, or things like this forum) may not necessarily realize this fact.  Too often the "non-food use" message is left out or assumed to be obvious.,....... and for many people, particularly the less experienced, it is NOT obvious.   

 

Additionally another related point I make is that just because someone is a "famous ceramic artist" and is seen absolutely everywhere and in every significant exhibition and other venue ....... and their work is absolutely stunning........ that does NOT guarantee that they have a solid technical understanding of things like glaze chemistry or firing theory or the like.  SO it is possible that the technical information they share is not all that accurate.  That does not take away from the visual power of claywork they produce.

 

best,

 

................john

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Guest JBaymore

Ahhhhh... I missed the rutile there also...... that will add iron and titanium.  Won't affect the flux unity.  Will up the metalic oxide content though.

 

best,

 

...............john

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I agree with John. If you post a glaze that is not food safe, you should mention that. Most people looking for glazes are looking for recipes that are most likely food safe. Yes, everyone is responsible for getting glazes tested, but if it doesn't even come close to food safe, they need to know. If for no other reason than not wasting their time with testing it.

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Guest JBaymore

Recalc with the rutile put in.........  

 

Ferro Frit 3134.............     7.00 
  Talc........................    17.00 
  OM #4 Ball Clay.............    25.00 
  Silica......................     6.00 
  Iron Oxide Red..............    10.00 
  Copper Carbonate............     2.70 
  Manganese Dioxide...........    21.50 
  Rutile......................    11.00 
                              =========
                                 100.20

          CaO       0.10*    
          MgO       0.28*    
          K2O       0.01*    
          Na2O      0.03*   
          TiO2      0.30    
          Al2O3     0.17     
          B2O3      0.05     
          SiO2      1.28    
          Fe2O3     0.16    
          MnO2      0.58*   
          ZrO2      0.00     
                        
           Thermal Expansion:    6.97
              Formula Weight:  217.35
 

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I used Insight Level II also but I've got a bug in the program and copper isn't recognized. One last point on that amount of MnO2, the firing fumes coming off are going to be nasty to say the least, 

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I have a sweet black glaze for cone 10

You could tweek it for cone 6

Its only colorant is cobalt ox at about 3-4% if I recall-this may put you out as its a bit pricy but its very stable without all the other colorants in a lot of blacks.

the other two ingredients are

Nepy sye

and  Alberta slip clay

You would need to flux it more to work at lower temps

It now has a range of cone 9-11 from metallic gunmetal (cone 9)to shiny gloss at higher temps

Its out in studio and I'm not now

Mark

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Ravenscrag Black ^6

 

Ravenscrag slip 80

3134  20

RIO  13

Cobalt Ox  0.50  

Chrome Ox  0.50 

 

CaO 0.57* 7.32 8.96
MgO 0.15* 1.39 2.36
K2O 0.12* 2.47 1.80
Na2O 0.16* 2.25 2.49
TiO2 0.02 0.32 0.27
Al2O3 0.45 10.36 6.97
B2O3 0.27 4.23 4.17
SiO2 4.32 59.08 67.45
CoO 0.02 0.29 0.26
Fe2O3 0.34 12.30 5.27

Cost: 0.00
Calculated LOI: 3.76
Imposed LOI:
Si:Al: 9.68
SiB:Al: 10.27
Thermal Expansion: 7.24
Formula Weight: 439.66

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Min are you happy with ravenscrag glazes? Do you use other ravenscrag based glazes? I've read up on them looks very promising.....

 

Wish I could use them  but the expansion is too high for the pseudo porcelain I'm currently using. Several people in the guild I go to use them on stoneware with success.

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Wish I could use them  but the expansion is too high for the pseudo porcelain I'm currently using. Several people in the guild I go to use them on stoneware with success.

Does this mean the same as porcelain shrinks too much for the glaze.

How would one correct this with traditional glazes?

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Guest JBaymore

Biglou,

 

There is a property of ceramic materials called Coefficient of (Reversible) Thermal Expansion......usually abbreviated C.O.E. or COE.  What it means is that upon heating all ceramic materials expand a certain amount.  Upon cooling they also shrink a certain amount.  Hence my appending of the term "reversible" to make it conceptually clearer.

 

This is NOT the shrinkage that happens when clay and glass forming materials are heated to mature them.  Important point to understand.  That shrinkage is usually called firing shrinkage.

 

The goal is to have the COE of the FIRED Body and the COE of the FIRED glaze layer in roughly similar ranges.  This means that the glaze "fits" the clay body.  If the mismatch in this expansion number if too far off..... then the glaze wither shrinkis MORE than the claybody as the kiln cools.... or the glaze shrinks LESS than the claybody.

 

Glass is striong in comptression, and weak in tension.  If the glaze shrinks MORE than the claybopdy, then the glaze eventually relieves this tension by cracking as it is trying to be pulled apart...... and you get the thing we call crazing.

 

If the glaze shrinks LESS than the claybody...... the layer of glass gets put under compression pressure... and eventially it shears off the bond with the undelying clay body (usually at edges or sharp breaks in curves).... and you get what we call shivering.

 

A particularly problematic defect is when you put a glaze that shrinks LESS than the claybody on the inside of a form, and one that shrinks MORE on the outsisde.  The stress across the body can cause the piece to literally explode into pieces in the cooling kiln.  WORSE... if the differential is very close to the general strength of the claybody of the form...... you can get a piece that is like a ticking timebomb.  Take the bowl with this condition and drop in some hot soup... and BANG!

 

best,

 

...............john

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