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C.Banks

clay plasticity/water content

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4 minutes ago, glazenerd said:

CB:

i knew when you first started posting that you had a working knowledge of clay. All I am doing is connecting the dots: many websites about clay formulation: but very few give the theorem of why. 

 

I was called away and the hurried tone was more abrupt than i intended.

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Measuring the plasticity of clays: A review

"Plasticity is the outstanding property of clay–water systems. It is the property a substance has when deformed continuously under a finite force. When the force is removed or reduced, the shape is maintained. Mineralogical composition, particle size distribution, organic substances and additives can affect the plasticity of clays. Several measuring techniques and devices were proposed to determine the optimal water content in a clay body required to allow this body to be plastically deformed by shaping. In this review, methods of evaluating the plasticity of clay–water systems are presented. Despite the advance in the theory of the plasticity and the methods of measurement, a common procedure for all types of materials does not exist. The most important methods are those that simulate the conditions of real processing." (F.A.Andradea, H.A.Al-Qureshiab, D.Hotzaac, https://www.sciencedirect.com/science/article/pii/S0169131710003601)

This explains plasticity and some testing procedures. I thought a link might help anyone else looking over the edge of this rabbit hole.

Edited by C.Banks

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Understanding Clay Body Formulation

"This three-part series will discuss the many business and technical issues that should be considered when creating/evaluating a clay body formulation. " (Jeff Zamek, https://www.ceramicindustry.com/articles/90298-ppp-evaluating-clays)

Another helpful online resource for anyone else mucking about at the bottom of a hole.

Edited by C.Banks

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20 hours ago, glazenerd said:

At cone 10 -2.89 to 3.19% molar KnaO.   Si/Al should not exceed 5:0 , the lower this number is: the stronger the body  if you are wood or salt firing where thermal resistance/ shock is needed: keeping SiAL closer to 4.0 helps.

These numbers look very specific. Do they come from a chart or formula?

Plainsman has a clay I like and because they are generous with their data, unlike some others I won't mention, I can use them as a bit of a guideline.

H555

 CaO       0.6
 K2O       2.0
 MgO       0.5
 Na2O      0.3
 TiO2      0.7
 Al2O3    20.9
 P2O5      0.0
 SiO2     65.5
 Fe2O3     1.1
 MnO       0.0
 LOI       8.3%

This is, I'm presuming, a percent by weight but I can still get a sense of where the Si:Al falls in relation to KNaO. I'm sure there is a way to input the percents into Hyperglaze and convert them but I'm tired of trying and failing.

and I just remembered about a garage sale I'm missing

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The CnC version looks like it has a nice Si:Al right out of the box. The molar KNaO is only 2.66% but it's not far off.  
              
Code Number:  CNC                                Code Number: new Plainsman clay
=========================================     =========================================
                                              
  EP Kaolin...................    20.00         EP Kaolin...................    25.00
  Silica......................    20.00         Silica......................    15.00
  Custer Feldspar.............    20.00         Custer Feldspar.............    20.00
  Hawthorne Bond..............    20.00         A2 Ball Clay................    20.00
  C & C Ball Clay.............    20.00         Plainsman Fire Clay.........    20.00
                              =========                                     =========
                                 100.00                                        100.00
                                              
  Oxide   Formula  Analysis    Molar%           Oxide   Formula  Analysis    Molar%
  CaO       0.00     0.19%w    0.23%m           CaO       0.00     0.21%w    0.26%m
  MgO       0.00     0.21%w    0.36%m           MgO       0.00     0.16%w    0.28%m
  K2O       0.03     2.59%w    1.87%m           K2O       0.03     2.86%w    2.07%m
  Na2O      0.01     0.72%w    0.79%m           Na2O      0.01     0.89%w    0.98%m
  P2O5      0.00     0.05%w    0.02%m           P2O5      0.00     0.06%w    0.03%m
  TiO2      0.01     0.84%w    0.71%m           TiO2      0.00     0.41%w    0.35%m
  Al2O3     0.23    24.85%w   16.59%m           Al2O3     0.22    23.82%w   15.87%m
  SiO2      1.08    69.84%w   79.12%m           SiO2      1.08    70.49%w   79.71%m
  Fe2O3     0.00     0.70%w    0.30%m           Fe2O3     0.01     1.08%w    0.46%m
                                              
                        Cost:    0.08                                 Cost:    0.08
              Calculated LOI:    6.70                       Calculated LOI:    7.62
                 Imposed LOI:                                  Imposed LOI:
                       Si:Al:    4.77                                Si:Al:    5.02
                      SiB:Al:    4.77                               SiB:Al:    5.02
           Thermal Expansion:  221.22                    Thermal Expansion:  237.63
              Formula Weight:   93.30                       Formula Weight:   92.38
                                              
                 Recipe Date: 2019-01-27                       Recipe Date: 2019-01-26
                Today's Date: 27/01/2019                      Today's Date: 27/01/2019
           Recipe name or ID: 184                        Recipe name or ID: 180
                    Location:                                     Location:
                   Typecodes:                                    Typecodes:
                  Batch Size: 0                                 Batch Size: 0
                                              
STANDARD.XML                                  STANDARD.XML
                                              
Edited by C.Banks

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CB

those numbers came from an expansive database I have been collecting. The lower and upper 10% were omitted because they were custom mixes for specific purposes. The median values I tested for absorption. 

Study the LOI: notice when kaolin goes up, the LOI goes up. When kaolin goes down and ball clay goes up: the LOI lowers. Silica and feldspar both have LOI under 0.50%. 

If you read the description of the Plainsman clay you posted: "fine grained."  If the entire body is fine particle then you can lower KnaO a bit, but as the % of large grain fire clay increases; KnaO likewise increases.

So if both recipes have 20% spar additions; then what change in recipe caused the molar% to change? 

Tom

 

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clay                                          clay
Code Number: NPC2                             Code Number: NPC3
=========================================     =========================================
                                              
  EP Kaolin...................    25.00         EP Kaolin...................    25.00
  A2 Ball Clay................    15.00         A2 Ball Clay................    15.00
  Plainsman Fire Clay.........    20.00         Plainsman Fire Clay.........    25.00
  Custer Feldspar.............    20.00         Custer Feldspar.............    20.00
  Silica......................    20.00         Silica......................    15.00
                              =========                                     =========
                                 100.00                                        100.00
                                              
  Oxide   Formula  Analysis    Molar%           Oxide   Formula  Analysis    Molar%
  CaO       0.00     0.20%w    0.24%m           CaO       0.00     0.21%w    0.25%m
  MgO       0.00     0.14%w    0.24%m           MgO       0.00     0.15%w    0.26%m
  K2O       0.03     2.81%w    2.01%m           K2O       0.03     2.94%w    2.12%m
  Na2O      0.01     0.88%w    0.96%m           Na2O      0.01     0.94%w    1.04%m
  P2O5      0.00     0.06%w    0.03%m           P2O5      0.00     0.06%w    0.03%m
  TiO2      0.00     0.37%w    0.31%m           TiO2      0.00     0.41%w    0.35%m
  Al2O3     0.21    22.65%w   15.00%m           Al2O3     0.22    24.22%w   16.17%m
  SiO2      1.11    71.91%w   80.80%m           SiO2      1.08    69.98%w   79.32%m
  Fe2O3     0.01     0.98%w    0.41%m           Fe2O3     0.01     1.09%w    0.46%m
                                              
                        Cost:    0.08                                 Cost:    0.08
              Calculated LOI:    7.09                       Calculated LOI:    7.52
                 Imposed LOI:                                  Imposed LOI:
                       Si:Al:    5.39                                Si:Al:    4.90
                      SiB:Al:    5.39                               SiB:Al:    4.90
           Thermal Expansion:  232.41                    Thermal Expansion:  242.83
              Formula Weight:   92.91                       Formula Weight:   92.48
                                              
                 Recipe Date: 2019-01-27                       Recipe Date:
                Today's Date: 28/01/2019                      Today's Date: 28/01/2019
           Recipe name or ID: 185                        Recipe name or ID: 186
                    Location:                                     Location:
                   Typecodes:                                    Typecodes:
                  Batch Size: 0                                 Batch Size: 0
                                              
STANDARD.XML                                  STANDARD.XML
                                              
Edited by C.Banks

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20 minutes ago, glazenerd said:

So if both recipes have 20% spar additions; then what change in recipe caused the molar% to change? 

The easy answer is the fireclay but I have a suspicion this is not what you are getting at.

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27 minutes ago, glazenerd said:

 If the entire body is fine particle then you can lower KnaO a bit, but as the % of large grain fire clay increases; KnaO likewise increases. 

I'm unsure how particle size increases KNaO amounts.

Unless the KNaO amounts must be increased out of necessity.

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EPK has a formula weight of 272.92, and OM4 is 390.40.

without getting into finite chemistry: ball clay is denser than kaolin. Being denser, it dilutes the concentration (molar%).

2 hours ago, C.Banks said:

I'm unsure how particle size increases KNaO amounts.

Unless the KNaO amounts must be increased out of necessity.

The temperature & flux required to melt. 400 mesh, 200 mesh, 100 mesh changes. Actually it plays into particle distribution as well. The higher the % of large particle fire clay! coupled with the actual particle size: means finer mesh must increase along with the KnaO to encapsulate them.  As this USB pic shows a cone 6 body with 15% 35 mesh Hawthorne bond. 

large.1869582075_MeshDistribution.jpg.4ba4192aaa9b62081132e0d3123675dc.jpg

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I was trying to understand this in terms of particle size and surface are but if large particle fireclay has less surface area this should, in my mind, mean less KNaO is required to encapsulate.

More dense, smaller particles have more surface area so would require more KNaO to encapsulate.

:unsure:

"ball clay is denser than kaolin. Being denser, it dilutes the concentration (molar%) "

Dilute to indicate a weaker solution so less available ... KNaO?

Edited by C.Banks

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I should have noted earlier; the KnaO levels were for functional use. If non functional, much more freedom.

in stoneware, particle distribution is just as relative as KnaO levels.

http://www.christyco.com/pdf/cmc/hawthorn_bond.pdf.  See mesh distribution at bottom of page.

in my testing, once I crossed 17% recipe addition of Hawthorne 35m, I noticed absorption climbing. I compensated by increasing fines and KnaO. I ran a series of tests using 1200 mesh SiC as a tracer to see how fine particles distributed in the body. I found it interesting that they tended to pack around large particle 35-60 mesh.

Knao molar% changes because formula weight increases. Solution is more relative to liquids. You have several recipes posted: mix them, fire them, and test them.

one way to see how individual materials effect KnaO levels is using your glaze calculator.

80% silica 20% Custer! then 80% alumina, 20% Custer! then 80% EPK, 20% Custer! then 80% OM4, 20% Custer  easier sometimes to see it.

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6 hours ago, glazenerd said:

You have several recipes posted: mix them, fire them, and test them.

That's the plan as long the three I'm looking don't have any obvious issues like creeping LOI values.

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On 1/27/2019 at 5:38 PM, glazenerd said:

ball clay is denser than kaolin. Being denser, it dilutes the concentration (molar%)

My suggestion of a 'solution' was my way of trying to understand a dense (fine?) kaolin 'diluting' a molar %

12 hours ago, glazenerd said:

Knao molar% changes because formula weight increases. Solution is more relative to liquids.

I'm sure more of this will will sink in over time. I have to re-read stuff  to try to untangle and think through the more complicated ideas.

I'm looking forward trying these adjustments when my materials arrive. I may have been able to stumble around on my own but this save me a bunch of trial and error and error.

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After a few tests this clay still requires about the same water.

I'm hoping when the studio comes out of winter storage the performance on the wheel might improve.

I'm looking at dropping the epk alltogether. I knew it was a bit out of place next to a fireclay.

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