**Adjusting the SAS Formula** - **Part 2** - FOR YOUR SPECIFIC PLASTICITY PREFERENCE.

The recipes given as examples above, include the amount of ball clay I prefer to achieve the plasticity that I like. There is however a minimum amount of fines required to encapsulate the large particles of fire clay.

Silicon Carbide was used as a tracer in this blend experiment to establish a visible marker. The large particle in the center of the picture is completely encapsulated with SiC tracers. In this particular blend experiment; 15% of large particle (category one) fire clay was used. While the interpretation of data is somewhat subjective: some will view it as overly populated, others will view it as acceptable. The baseline objective is to formulate a body that is vitrified (encapsulated) for functional use. While porcelain does become fully vitrified: stoneware is acceptable with absorption around one percent. So the primary goal of SAS formulation is to provide enough sub-micron particles to completely encapsulate large mesh fire clay: coupled with the correct Si/Al levels, and the adequate flux molarity. The end goal being functional use. However, the SAS formula can be used for non-functional bodies to create the strongest, densest bodies achievable.

The minimum sub micron fines required for SAS formulation is 0.75% of category one fire clay.

EX> 15% category one fire clay times 0.75 = 11.25 Round up to 12 ( Clay formula does not require the precision of glaze.)

The easiest way to establish a median SAS value that reflects your personal preferences for plasticity, is to convert one of your favorite recipes to the SAS formula. The final median SAS value given after you have adjusted for large particle fire clay is your preferred range. However, if that median value falls below the minimum required for functional use: then adjustments need to be made.

*Minimum sub- micron particles*

15 parts Hawthorne 40m 15 parts x 20 SAS = 340 SAS x 1.27 = 381 SAS Cat. 1

**Minimum fines required: 15 parts fireclay x 0.75= 11.25 round up to 12 *

12 parts ball clay 12 parts x 25 SAS = 300 SAS Cat.2

48 parts Imco 400 200m 48 parts x 21 SAS = 1008 SAS Cat.2

10 parts silica 10 parts x 7 SAS reporting value. Cat.3

13 feldspar 13 parts x 9 SAS reporting value. Cat.4

1689 SAS divided by 77 parts (clay only) = 21.94 median SAS

This would be a lower plasticity body, heavy body; suitable for a cone 10 firing. It would be suspect however for a cone 6 application. The high population of 200 mesh category 2 clay would be suspect if flux levels were too low: or if it was fired incorrectly. For cone 6, I would like to see more fines.

15 parts Hawthorne 40m 15 parts x 20 SAS = 340 SAS x 1.27 = 381 SAS Cat.1

*Minimum fines required: 15 parts fireclay x 0.75= 11.25 round up to 12

12 parts ball clay 12 parts x 25 SAS = 300 SAS Cat.2

**38 parts Imco 400 200m ** 38 parts x 21 SAS = 798 SAS Cat.2

**10 parts EPK ** 10 parts x 28.56 = 286 SAS Cat.2

10 parts silica 10 parts x 7 SAS reporting value. Cat.3

13 feldspar 13 parts x 9 SAS reporting value. Cat.4

1765 SAS divided by 77 parts (clay only) = 22.92 median SAS

Or if you like high plasticity bodies:

15 parts Hawthorne 40m 15 parts x 20 SAS = 340 SAS x 1.27 = 381 SAS Cat. 1

*Minimum fines required: 15 parts fireclay x 0.75= 11.25 round up to 12

**18 parts ball clay** 18 parts x 25 SAS = 450 SAS Cat.2

- Plus 6 additional ball clay for plasticity:

32 parts Imco 400 200m 32 parts x 21 SAS = 672 SAS Cat.2

10 parts EPK 10 parts x 28.56 = 286 SAS Cat.2

10 parts silica 10 parts x 7 SAS reporting value. Cat.3

13 feldspar 13 parts x 9 SAS reporting value. Cat.4

1789 SAS divided by 77 parts (clay only) = 23.23 median SAS

Want more plasticity: then use a higher SAS rated ball clay. Remember, as the SAS value rises: the PSD becomes finer, and the plasticity increases.

15 parts Hawthorne 40m 15 parts x 20 SAS = 340 SAS x 1.27 = 381 SAS Cat. 1

*Minimum fines required: 15 parts fireclay x 0.75= 11.25 round up to 12

18 parts ball clay 18 parts x **28 SAS** = 504 SAS Cat.2

• Plus 6 additional ball clay for plasticity:

32 parts Imco 400 200m 32 parts x 21 SAS = 672 SAS Cat.2

10 parts EPK 10 parts x 28.56 = 286 SAS Cat.2

10 parts silica 10 parts x 7 SAS reporting value. Cat.3

13 feldspar 13 parts x 9 SAS reporting value. Cat.4

1843 SAS divided by 77 parts (clay only) = 23.93 median SAS

This body works fine using a SAS 25 ball clay, if you want more plasticity use SAS 28 ball clay. If you plan on making grog additions: you are adding more large particles. Compensate by using only SAS 28 clay, or increase the EPK slightly, and subtract that change from the Imco 400.

As you can see by the final median SAS values: formulation falls into the mid 20 range: 22.00 up to 24.00 SAS. This range is acceptable for most bodies designed for functional use. However, after absorption testing and weep testing: if a problem exists: then increase the sub micron fines; either by increased ball clay, finer ball caly (higher SAS), or additions of EPK (SAS 28.56)

Nerd