OPACIFIERS

Miscellaneous

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Raw Mineral: Yes
Generic: No

Notes

(Richard Willis)

For the most part, opaque-making agents are metals, though many non-metals, such as carbon and sulfur, will enhance if not directly produce varying effects contributing to opacity. Tin is one of the strongest and most used opacifiers at any temperature: an addition of 10% of total molecular weight of most any otherwise transparent, uncolored glaze formula will whiten the glaze. Any opacifier, tin especially, added to colored transparent glaze formulas will lighten or dull the colors as well as opacify them. Opacifying strengths vary greatly, and depend largely on firing temperatures and conditions and with what other ingredients the agent is reacting to. As a rule of thumb, the weaker opacifiers at temperatures under 1100ºC are the alkalis, though they become very strong opacifiers over 1100ºC, and are often preferred over tin for whitening in over 1300ºC glazes — on porcelains, for example.
The listing below is a guide, not a definitive overall solution, toward finding the right opacifier for the right occasion. Generally, opacifying agents should be used with caution: increasing amounts at random simply on the thought that a higher percentage of opacifier will increase the glazes opacity is often counterproductive; and the same is true in reverse: reducing an agent's percentage is not always the right direction toward diminishing opacity without prejudicial results. On further guides, note in tried and proven formulas and recipes specifically using opacifiers what percentages are used with what other ingredients in particular, and at what temperatures and in what conditions is the firing to proceed.
commonly used molecules
Sb₂O₃ or Na₂O, Sb₂O₅, 1/2 H₂O — whites w/ alkalines, cream yellows w/ leads; calcinate (900º) to avoid bubbles.4-6% w/ borax and alkalines and/or 1% w/ leads
CeO₂— mattes, alone; creams and whites when reinforced by Sn or Zr
ZnO or ZnO, Al₂O₃— stronger w/ Ti.strengthens Ca,Ba, Mg and Al.Best w/ Pb
ZrO₂ or ZrSiO₄ — industrial (large quantities) replacement for more expensive SnO₂ — solid whites with either alkalines or leads
CaO, ZrO₂, SiO₂ or MgO, ZrO₂, SiO₂or BaO, ZrO₂, SiO₂ or ZnO, ZrO₂, SiO₂— common frit combos when formulated with Al and B and/or Pbto give whites — can produce “virtual” frits when calcinated prior to mixing with either crude or fritted boraxes and/or leads — can be used alone to whiten a transparent recipe, to gloss and/or whiten a matte recipe, or t o strengthen and whiten a borax recipe — if they are all used together in one batch with borax and/or lead and Al, depending on the proportions of borax and/or lead and Al, the opacification can run the full gambit from gloss-white to chalk-white in an equally long temperaturerange of 650to 1000^ºC
CaF₂— calcinate to avoid bubbles — with ochres and alkalines can give “rock-tan” in emulation of travertine rock
As₂O₃— soluble in water —strong color enhancer w/ Pb
Ca₃ (PO₄)₂ or Mg₃(PO₄)₂ or Na₃P₂O₇or Na₂HPO₄, H₂O or Na₃PO₄, (0H₂) — phosphates normally associated with high-fire (1100º plus) but are good candidates for low-fire chalk whites when combined withliberal portions of Si and B/Pb low fusion-temperature frits
commonly used elements
aluminum Al — barium Ba — magnesium Mg — zinc Zn — antimony Sb — calcium Ca — tin Sn — zirconium Zr — arsenic — As — iron — Fe — titanium Ti
popular molecular forms
CaF — Al₂O₃ — MgCO₃— TiO₂— NaF — As₂O₃ — ZrSiO₄—SnO₂ — FeO — Sb₂O₃ — BaCO₃ — Ca(PO₄)₂ — ZnS — CaO, Sb₂O₃— Pb₃(SbO₄)₂— 3MgO, 4SiO₂ — ZrO CaO₃, MgCO₃— 2CaO, 5MgO, 8SiO₂₂

Authors

Richard Willis (Owner)

XML

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<notes>
<note>For the most part, opaque-making agents are metals, though many non-metals, such as carbon and sulfur, will enhance if not directly produce varying effects contributing to opacity. Tin is one of the strongest and most used opacifiers at any temperature: an addition of 10% of total molecular weight of most any otherwise transparent, uncolored glaze formula will whiten the glaze. Any opacifier, tin especially, added to colored transparent glaze formulas will lighten or dull the colors as well as opacify them.
Opacifying strengths vary greatly, and depend largely on firing temperatures and conditions and with what other ingredients the agent is reacting to. As a rule of thumb, the weaker opacifiers at temperatures under 1100&ordm;C are the alkalis, though they become very strong opacifiers over 1100&ordm;C, and are often preferred over tin for whitening in over 1300&ordm;C glazes &#151; on porcelains, for example. 
The listing below is a guide, not a definitive overall solution, toward finding the right opacifier for the right occasion. Generally, opacifying agents should be used with caution: increasing amounts at random simply on the thought that a higher percentage of opacifier will increase the glazes opacity is often counterproductive; and the same is true in reverse: reducing an agent\'s percentage is not always the right direction toward diminishing opacity without prejudicial results. On further guides, note in
tried and proven formulas and recipes specifically using opacifiers what percentages are used with what other ingredients in particular, and at what temperatures and in what conditions is the firing to proceed. 
commonly used molecules 
Sb2O3 or Na2O, Sb2O5, 1/2 H2O &#151; whites w/ alkalines, cream yellows w/ leads; calcinate (900&ordm;) to avoid bubbles. 4-6% w/ borax and alkalines and/or 1% w/ leads 
CeO2 &#151; mattes, alone; creams and whites when reinforced by Sn or Zr 
ZnO or ZnO, Al2O3 &#151; stronger w/ Ti. strengthens Ca, Ba, Mg and Al. Best w/ Pb 
ZrO2 or ZrSiO4 &#151; industrial (large quantities) replacement for more expensive SnO2 &#151; solid whites with either alkalines or leads 
CaO, ZrO2, SiO2 or MgO, ZrO2, SiO2 
or BaO, ZrO2, SiO2 or ZnO, ZrO2, SiO2 &#151; common frit combos when formulated with Al and B and/or Pb to give whites &#151; can produce &#147;virtual&#148; frits when calcinated prior to mixing with either crude or fritted boraxes and/or leads &#151; can be used alone to whiten a transparent recipe, to gloss and/or whiten a matte recipe, or t
o strengthen and whiten a borax recipe &#151; if they are all used together in one batch with borax and/or lead and Al, depending on the proportions of borax and/or lead and Al, the opacification can run the full gambit from gloss-white to chalk-white in an equally long temperature range of 650 to 1000&ordm;C 
CaF2 &#151; calcinate to avoid bubbles &#151; with ochres and alkalines can give &#147;rock-tan&#148; in emulation of travertine rock 
As2O3 &#151; soluble in water &#151;strong color enhancer w/ Pb 
Ca3 (PO4)2 or Mg3(PO4)2 or Na3P2O7 
or Na2HPO4, H2O or Na3PO4, (0H2) &#151; phosphates normally associated with high-fire (1100&ordm; plus) but are good candidates for low-fire chalk whites when combined with liberal portions of Si and B/Pb low fusion-temperature frits 
commonly used elements 
aluminum Al &#151; barium Ba &#151; magnesium Mg &#151; zinc Zn &#151; antimony Sb &#151; calcium Ca &#151; tin Sn &#151; zirconium Zr &#151; arsenic &#151; As &#151; iron &#151; Fe &#151; titanium Ti 
popular molecular forms 
CaF &#151; Al2O3 &#151; MgCO3 &#151; TiO2 &#151; NaF &#151; As2O3 &#151; ZrSiO4 &#151; SnO2 &#151; FeO &#151; Sb2O3 &#151; BaCO3
 &#151; Ca(PO4)2 &#151; ZnS &#151; CaO, Sb2O3 &#151; Pb3(SbO4)2 &#151; 3MgO, 4SiO2 &#151; ZrO CaO3, MgCO3 &#151; 2CaO, 5MgO, 8SiO22</FON
T> 

</note>
</notes>
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OPACIFIERS

Miscellaneous

Notes

(Richard Willis)

Authors

XML