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Barnard Slip

High Iron Clay

Barnard clay has long been used by potters as a source of iron in dark firing glazes. It offers price advantages over using iron oxide and being a clay aids in suspending the materials in the slurry. Barnard has proven valuable for iron slip glazes requiring high clay content. For example, a mixture of 90% Barnard and 20% calcium carbonate will produce a nearly black glaze around cone 9.

Published chemistries appear to be highly variable. We have seen iron amounts as low as 14% and as high as 34% (the other oxides are likewise variable).

Barnard clay is a silty material with very low plasticity; so low that it is difficult to form test specimens from it in the plastic state. The material is extremely messy to work with and stains containers and everything it touches. There is some variation in the color (and thus of thevfired results of glazes and slips employing it).

This is one of the most stained clay materials available. Fired bars are very dark brown at cone 02 proceeding to black at cone 4. At cone 6 it is beginning to melt.

To duplicate this material the base clay needs to have low plasticity and be high in iron and silica and low in alumina and flux. Since iron oxide and silica need to be added flux containing clays could possibly be diluted enough to work. If you would like more information please email us and we can give you trial recipes in return for your reports on their testing.

Out Bound Links

• (Materials - Unspecified) Albany Slip - High iron silty low melting clay

  New York Slip, Albany Clay

• (Materials - Unspecified) Ravenscrag Slip - Silty fusible low iron clay
• (Materials - Substitute) SG 758 - Barnard Slip substitute from Laguna Clays

  Barnard Clay Sub SG758

• (Typecodes) 1: CLO - Clay Other
• (MDT) Ron Roy

  This is the traditional Ron Roy materials file. He...

• (MDT) North America

  The decision about what materials to include in th...

XML for Import into INSIGHT

<?xml version="1.0" encoding="UTF-8"?>
<material name="Barnard Slip" descrip="High Iron Clay" searchkey="Blackbird Slip, Blackbird Clay, Barnard Clay" loi="0.00" casnumber="70694-09-6">
<oxides>
<oxide symbol="CaO" name="Calcium Oxide, Calcia" status="" percent="0.600" tolerance=""/>
<oxide symbol="MgO" name="Magnesium Oxide, Magnesia" status="" percent="0.700" tolerance=""/>
<oxide symbol="K2O" name="Potassium Oxide" status="" percent="1.100" tolerance=""/>
<oxide symbol="Na2O" name="Sodium Oxide, Soda" status="" percent="0.600" tolerance=""/>
<oxide symbol="TiO2" name="Titanium Dioxide, Titania" status="" percent="0.200" tolerance=""/>
<oxide symbol="Al2O3" name="Aluminum Oxide, Alumina" status="" percent="7.600" tolerance=""/>
<oxide symbol="SiO2" name="Silicon Dioxide, Silica" status="" percent="47.000" tolerance=""/>
<oxide symbol="Fe2O3" name="Iron Oxide, Ferric Oxide" status="" percent="33.900" tolerance=""/>
</oxides>
<volatiles>
<volatile symbol="LOI" name="Loss on Ignition" percent="8.310" tolerance=""/>
</volatiles>
</material>

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