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Redart

Red Firing Earthenware

Chemistry %

CaO0.26
MgO1.59
K2O4.15
Na2O0.38
P2O50.22
TiO21.09
Al2O315.51
SiO264.95
Fe2O37.05
 

Volatiles %

LOI4.80
WABS - Water absorption Cone 04: 11% Cone 2: 1%
FSHR - Firing Shrinkage Cone 04: 3% Cone 2: 8%
DSHR - Drying Shrinkage 5.5%

Redart is a red firing earthenware of moderate plasticity and low shrinkage. It fires light orange to dark red depending on firing temperature from cone 06 to 3. It fires much stronger and denser at cone 04 than 06 and achieves its best color/strength compromise at cone 02 and gives deep red color and stoneware properties at cone 1. It is airfloated to 200 mesh and is very clean and has a long firing range. This is a very popular ingredient in clay bodies made across North America and it has been available for many years.

This material is quite high in iron thus the powder is a deep red color and quite messy to work with. Redart is also used by potters in glaze recipes, sometimes up to 60%.

Redart can be used as a primary component in plastic modeling and throwing bodies, however some plastic additions of ball clay will be necessary. It can be used as a casting body without any additions, although it is desirable to diversify recipes to achieve better consistency and less dependence on the quality of one material alone.

While redart can be used as a source of iron in high temperature bodies, it will produce brown rather than red coloration. This is because the fluxes are intimately mixed with the iron and fuse it to a darker color. To get red in oxidation or reduction at higher temperatures you must use refractory clays with iron or iron bearing fireclays. However there is good reason not to use low fire reds as fluxes in high fire bodies: The fluxes in the red clays don't dissolve cristobalite like feldspar does, the result can be thermal expansion related ware failure.

This material is mined from a large deposit and the company is confident in its consistency and long term availability.

Sample body recipes for low fire terra cotta:

Redart Casting mix #1062
---------------
10 Kaolin
50 Redart
25 Nepheline Syenite
15 Large Particle size kaolin
33.7 Water
0.15 Soda Ash
0.65 N Brand Sodium Silicate

For redder color you can replace the kaolin with more Redart but dry strength will be lower. You can even use straight redart for casting.

Redart very plastic throwing body #3322A
----------------
40 Redart
40 Banta Red Clay
10 Talc
10 Ball clay

This body has remarkably good plasticity yet its drying performance is also very good. It is melting by cone 4 and is quite vitreous by cone 02. Talc in low fire bodies can really improve drying while not reducing plasticity as much as other fillers, talc also increases the thermal expansion for better fit to commercial glazes.


Mechanisms

Out Bound Links

In Bound Links


Pictures
Test bars of Red art clay (left) fired from cone 06 (top) to 5 (bottom). On the right is Plainsman Blue Grey Plastic fired across a similar temperature range.


M2 (left) vs. Redart (right). These bars are fired from cone 04 to 4. Fired color is almost identical. M2 has a little more soluble salts and is a little more plastic. Redart casts better.


XML for Import into INSIGHT

<?xml version="1.0" encoding="UTF-8"?>
<material name="Redart" descrip="Red Firing Earthenware" searchkey="Red Art" loi="0.00" casnumber="70694-09-6">
<oxides>
<oxide symbol="CaO" name="Calcium Oxide, Calcia" status="" percent="0.260" tolerance=""/>
<oxide symbol="MgO" name="Magnesium Oxide, Magnesia" status="" percent="1.590" tolerance=""/>
<oxide symbol="K2O" name="Potassium Oxide" status="" percent="4.150" tolerance=""/>
<oxide symbol="Na2O" name="Sodium Oxide, Soda" status="" percent="0.380" tolerance=""/>
<oxide symbol="P2O5" name="Phosphorus Pentoxide" status="" percent="0.220" tolerance=""/>
<oxide symbol="TiO2" name="Titanium Dioxide, Titania" status="" percent="1.090" tolerance=""/>
<oxide symbol="Al2O3" name="Aluminum Oxide, Alumina" status="" percent="15.510" tolerance=""/>
<oxide symbol="SiO2" name="Silicon Dioxide, Silica" status="" percent="64.950" tolerance=""/>
<oxide symbol="Fe2O3" name="Iron Oxide, Ferric Oxide" status="" percent="7.050" tolerance=""/>
</oxides>
<volatiles>
<volatile symbol="LOI" name="Loss on Ignition" percent="4.800" tolerance=""/>
</volatiles>
</material>


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