Natural iron oxide pigments or iron oxide earth pigments, collectively referred to as iron oxides, comprise both oxides and oxide hydroxides of iron. Hematite (α-Fe2O3) is the most common iron oxide in red earth pigments and the iron oxide hydroxide goethite (α-FeOOH) is the most frequently found iron compound in yellow earth pigments. Umbers are brown earth pigments containing both oxides of iron and manganese.
Names for natural iron oxide pigments are complex and inconsistent. Yellow pigments based on iron oxide hydroxides are referred to by many different names, including goethite, limonite, raw sienna, Mars yellow, yellow earth, yellow ocher, yellow iron oxide, yellow hydrated oxide and iron hydroxide pigment. Similarly, references to natural red pigments, based on anhydrous iron oxide, are referred to with such names as hematite, red earth, red ocher, burnt sienna, Mars red and red iron oxide.
The problem is compounded further when manufacturers label synthetic iron oxide pigments with names typically associated only with earth pigments, such as a artificial yellow iron oxide labeled as yellow ochre.
The general term iron oxide pigment is an appropriate name when referring to both natural and synthetic materials that may contain mixtures of iron oxides and iron oxide hydroxides. The names earth and ocher are suitable when it is clear that the pigment comes from a natural source. Earth is a more general term, since ocher refers to a specific type of iron oxide deposit containing kaolinite (clay) and quartz. Hematite is used to differentiate the crushing of mineral hematite, which contains iron oxide in a finely divided form and is usually associated with clay or other minerals. Umber refers to a chemically distinct class of brown earth pigment containing manganese and iron.
The Colour Index (1982, 1:16-17, 120-122, 64-65) lists natural red iron oxide pigments as CI Pigment Red 102 (nos. 77015, 77491 and 77538). Synthetic red iron oxide pigments are listed as CI Pigment Red 101 (nos. 77015, 77491 and 77538). The natural and synthetic yellow iron oxide pigments are listed as CI Pigment Yellow 43 and 42 (no. 77492), respectively. CI Pigment Brown 6 and 7 (nos. 77491, 77492 and 77499) designate the synthetic and natural brown iron oxide pigments, including umbers.
Generally, we can summarize the various iron oxide pigment names and their Colour Index designations as follows:
Colour Index Pigment Names
Yellow Earth Pigments Pigment Yellow 43 Limonite, goethite, jarosite, yellow ocher, yellow earth, yellow iron oxide, raw sienna
Red Earth Pigments Pigment Red 102 Hematite, red earth, red ocher, burnt sienna, red iron oxide
Brown Earth Pigments Pigment Brown 7 Pyrolusite, umber, burnt umber
To determine whether a pigment is from a natural source, such as an earth iron oxide pigment, look for the Colour Index designation, such as Pigment Yellow 43 (PY43), Pigment Red 102 (PR102) or Pigment Brown 7 (PBr7).
George O'Hanlon-----------------------Natural Pigments888-361-5900http://naturalpigments.com
Thank you for the valuable information about earth iron oxide pigments. I find that each color in pigment format as different textures and can't be resolved or mixed same way. It would be great decussing such subject and what is the best way to desolve pigments powder?
Regards,
Mona
Pigment powders are not dissolved, but are mixed with paint vehicle. This forms a collodial suspension and not a solution, which is the result of dissolving one substance in another. To mix pigment powder with paint vehicle, does not require much. It can be done with a palette knife, but best results are obtained when using a muller on a flat, smooth slab of glass or stone.
Thank you Goerge,
You are right pigments do not get resolved for the fact that some colors remain very rough and sandy like. But what medium do you use to mix them with. I tried sulable wax, oil, safflower oil and others but they do not really give me the desirable result.
The texture of rough and sandy occurs with some pigments, but most pigments will benefit by using a muller on a stone or glass slab so that you can grind the mixture to a smooth paste.
Thank you once agian Goerge but you still did not tell me what do you miix the pigments with?!
You can mix it with linseed oil, walnut oil or if you intend to paint in encaustics with different types of waxes.
Thank you George, will try it and let you know. When y say Muller, did you mean electronic blender?
A muller is a simple hand tool used to grind pigments to make your own paint. Here is an example you can see.
Thank you George, I have visited the website and might make order form there in Walleck's do not have it here!
Are you well familiar with this website? Do you trust it to make orders from there?
Yes, I trust the web site and the company, because I am a director of the company, Natural Pigments.
HI GEORGE! I just wonder if you can give me some idea what would be the best Gesso preparation for canvas surface that would be a bit thinner in nature yet it will still enhance the canvas texture and would make a charcoal drawing lasts on it....thanks in advance for any information on this matter....
You need to describe some more specifics as to the materials you are using. By gesso do you mean acrylic gesso? What do you mean by the charcoal drawing last?
Acrylic dispersion grounds (we do not call this type of grond 'gesso,' because gesso is the Italian word for 'gypsum') are not absorbent, so charcoal will not adhere to this ground. Your only option is to use a fixative. Make sure the fixative contains a non-yellowing resin, such as ketone resins.
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