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Pioneer 2661 Talc

Alternate Names: Pioneer Ceramic Talc, Pioneer Talc, Pioneer 2882

Description: White Texas Talc

Oxide Analysis Formula
CaO 3.50% 0.08
MgO 29.50% 0.92
Al2O3 0.50% 0.01
SiO2 53.50% 1.12
Fe2O3 0.50% -
TiO2 0.10% -
K2O 0.30% -
LOI 11.00%n/a
Oxide Weight 110.21
Formula Weight 123.83


Now called AmTalc
Texas Talc has a darker grey raw color and a rounder fluffier particle than other talcs. However it fires very white and is desired for its consistency. It is commonly used in ceramic slurries for low temperature greenware. Pioneer talcs are non-asbestiform.

Various grades are available.

Acid Solubles: 2-4
pH: 9.5
LOI: 11.5
Water Solubles: -.1
Dry Brightness: 58-65
Dry Brightness after firing: 88+
Specific gravity: 2.7
Tapped Density: 75-85 lbs/ft3
Loose Density: 35-45 "
One Lb. Bulks, Gallons: .04
Shrinkage: 0.60
Oil Absorption: 32
Hegman Fineness: 1.0

Thru 200 mesh, %: 97.0
Thru 325 mesh, %: 85.0
Median Particle Size: 19.0 microns

2882 Talc is the same except:
Fe2O3: < .69
Dry Brightness: 62.0

Pioneer 1599 is a platy Texas general purpose industrial talc.

Related Information

Texas talc (left) and Montana talc (right)

Texas talc contains some amorphous carbon. The carbon is not stand-alone, but as CO2 in the dolomitic part of the ore. It produces ~7% LOI between 750-850C. Even though the powder color is so much darker in the raw form, it fires whiter! But there is more going on here. On paper, both contain about 0.5% Fe2O3. But the iron species in the two talcs are different. In Texas talcs, the iron is part of the crystal lattice. But, in the Montana material, that 0.5% Fe2O3 is an external iron oxide mineral species, a physical contaminant. While the Montana material fires much darker because of this that iron seems to have little affect on the color of the raw white powder.

Montana talc vs Texas talc - Powder fire at cone 6

Although this Montana talc (Silverline 303) is white as a raw material (vs. dark grey for the Texas material, Natural Minerals C-98), it does not fire nearly as white (even though their data sheets both claim 0.5% Fe2O3). The Montana material is often suitable as a substitute in glazes where percentages are low. If higher percentages are employed (e.g. 10% to achieve a silky matte) then color will darken if Montana talc is substituted for Texas talc. In bodies, where talc is used as a flux in low percentages (e.g. 1-3%) the color should be OK. In low temperature clay bodies, where talc was employed to adjust thermal expansion, as much as 50% is used - of course in these cases the color will be far too dark.

Permeability demonstration of Texas and Montana talcs

Texas talc (left) quickly absorbs all the water poured on it. Montana talc (right) resists whetting of the particles much more, the water is just sitting on top and has not penetrated at all.


Product Information
Replace Talc with Nepheline Syenite in low temperature white bodies
Materials Suzorite 325-PE
Materials Talc
A source of MgO for ceramic glazes, a flux or thermal expansion additive in clay bodies, also used in the manufacture of cordierite.
Materials Amtalc-C98
Materials Desertalc
Typecodes Flux Source
Materials that source Na2O, K2O, Li2O, CaO, MgO and other fluxes but are not feldspars or frits. Remember that materials can be flux sources but also perform many other roles. For example, talc is a flux in high temperature glazes, but a matting agent in low temperatures ones. It can also be a flux, a filler and an expansion increaser in bodies.
Hazards Talc Hazards Overview
Talc is invaluable in the ceramics industry, it is used as a glaze and body ingredient and as a parting a release agent in various processes. Is it safe?
Hazards Talc Toxicology
By Tony Hansen
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