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CALCIUM

Miscellaneous

• Family: Raw Mineral
• Region: None
• Mined At: Unspecified
• Raw Mineral: Yes
• Generic: No

Notes

(Richard Willis)

Element, with the symbol Ca and atomic weight of 40.08 Water insoluble
As does alumina, calcium oxide turns soluble metals, like lead, to insolubles. When used in its carbonate form, the normal way, as with all carbonates CO₂ is released (825ºC for calcium) and the escaping gas can create bubbles and leave pinholes if not then given time and temperature to smooth over.
Benefits are similar to those of lithium but at lower temperatures (under 1100ºC) as well as high temperatures. Though a strong flux with silica at low temperatures it is stronger still at high temperatures, thus a popular flux in porcelain clays and glazes.
Since insoluble it is a bit easier to add to recipes in oxide forms than are sodium and potassium without too much trouble in blending, but recommendable, nevertheless, to introduce via a clay or mineral containing it, such as the borates and feldspars and calcites when there is no strong reason to do otherwise. The “live” calciums (usually sulfates) should be avoided and guarded against at all cost. Plaster, for instance, will leave pockets of powder that not only resist adhesion to glazes but wi ll later absorb humidity, swell, and break up the clay or glaze around it.
water solubility & fusion ºC
— oxide — insoluble — 2570
— carbonate — insoluble — discomposes
— dolomite — insoluble — discomposes
— bone ash — breaks up in hot water — 1670
— fluor spar — insoluble — 1360
commonly used forms
— wollastonite CaO, SiO₂
— dolomite CaCO₃, MgCO₃
— calcinated oxide CaO
— nepheline talc 2CaO, 5MgO, 8SiO₂
— hydroxide (“dead”) Ca(OH)₂
— sulfate (plaster) CaSO₄, 2H₂O
— chloride CaCl₂, 6H₂O
— feldspar CaO, Al₂O₃, 2SiO₂
— fluor spar CaF₂
— borate 2CaO, 3B₂O₃, 5H₂O
— phosphate (bone ash) Ca(PO₄)₂
— carbonate (“Crete”, “white of Spain”, “Whiting”, etc.) CaCO₃

Authors

• Richard Willis (Owner)

XML

<?xml version="1.0" encoding="UTF-8"?>
<material name="CALCIUM" descrip="" generic="0" rawmineral="1" searchkey="" loi="0.00">
<families>
<family name="Raw Mineral"/>
</families>
<notes>
<note>Element, with the symbol Ca and atomic weight of 40.08 Water insoluble&lt;BR&gt;
As does alumina, calcium oxide turns soluble metals, like lead, to insolubles. When used in its carbonate form, the normal way, as with all carbonates CO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt; is released (825&amp;ordm;C for calcium) and the escaping gas can create bubbles and leave pinholes if not then given time and temperature to smooth over.&lt;BR&gt;
Benefits are similar to those of lithium but at lower temperatures (under 1100&amp;ordm;C) as well as high temperatures. Though a strong flux with silica at low temperatures it is stronger still at high temperatures, thus a popular flux in porcelain clays and glazes.&lt;BR&gt;
Since insoluble it is a bit easier to add to recipes in oxide forms than are sodium and potassium without too much trouble in blending, but recommendable, nevertheless, to introduce via a clay or mineral containing it, such as the borates and feldspars and calcites when there is no strong reason to do otherwise. The &amp;#147;live&amp;#148; calciums (usually sulfates) should be avoided and guarded against at all cost. Plaster, for instance, will leave pockets of powder that not only resist adhesion to glazes but wi
ll later absorb humidity, swell, and break up the clay or glaze around it.&lt;BR&gt;
&lt;B&gt;water solubility &amp;amp; fusion &amp;ordm;C&lt;/B&gt;&lt;BR&gt;
&amp;#151; oxide &amp;#151; insoluble &amp;#151; 2570&lt;BR&gt;
&amp;#151; carbonate &amp;#151; insoluble &amp;#151; discomposes&lt;BR&gt;
&amp;#151; dolomite &amp;#151; insoluble &amp;#151; discomposes&lt;BR&gt;
&amp;#151; bone ash &amp;#151; breaks up in hot water &amp;#151; 1670&lt;BR&gt;
&amp;#151; fluor spar &amp;#151; insoluble &amp;#151; 1360&lt;BR&gt;
&lt;B&gt;commonly used forms&lt;/B&gt;&lt;BR&gt;
&amp;#151; wollastonite CaO, SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;&amp;#151; dolomite CaCO&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;, MgCO&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;&lt;BR&gt;
&amp;#151; calcinated oxide CaO&lt;BR&gt;
&amp;#151; nepheline talc 2CaO, 5MgO, 8SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;&amp;#151; hydroxide (&amp;#147;dead&amp;#148;) Ca(OH)&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;&amp;#151; sulfate (plaster) CaSO&lt;FONT SIZE=2&gt;&lt;SUB&gt;4&lt;/SUB&gt;&lt;/FONT&gt;, 2H&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;BR&gt;
&amp;#151; chloride CaCl&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;, 6H&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;BR&gt;
&amp;#151; feldspar CaO, Al&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;, 2SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;&amp;#151; fluor spar CaF&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;&amp;#151; borate 2CaO, 3B&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;, 5H&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;BR&gt;
&amp;#151; phosphate (bone ash) Ca(PO&lt;FONT SIZE=2&gt;&lt;SUB&gt;4&lt;/SUB&gt;&lt;/FONT&gt;)&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;&amp;#151; carbonate (&amp;#147;Crete&amp;#148;, &amp;#147;white of Spain&amp;#148;, &amp;#147;Whiting&amp;#148;, etc.) CaCO&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;

</note>
</notes>
</material>

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