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Information about pigments we use in P.C. everyday. by Linda H. Dixon, MD
Synthetic iron oxides are manufactured to eliminate the contamination of naturally occurring iron oxides. These metals are basically inert, although iron oxide blacks (magnetite) do have magnetic properties. Iron oxides are a softer metal than titanium dioxide.Iron oxide molecules are crystals and are in different shapes. Some are spherical, others are rhomboids and yet others look like a pencil shaped crystal (long and narrow). Ultraviolet light can affect the crystalline structure and result in loss of color activity. Light fastness or "reflectance" describes a particle's ability to reflect light at a certain wavelength. Most synthetic iron
Common in inks used for tattooing, the carbon black particle is without shape or "amorphous" and the size is a tiny .03 microns. This means it is from 10-20 timessmaller in size than an iron oxide pigment particle. My personal belief is that this ultra-small size is why we will often see migration or "bleeding" of pigment into surrounding tissues when using carbon black based inks.
By definition, a pigment is a particle and NOT soluble in solution. If a colorant dissolves in solution then it becomes a dye. Various dispersal agents such as glycerin, ethyl alcohol, Witch Hazel, water, castor oil, propylene glycol and others are used to keep the particles from forming clumps.Remember that these particles are weakly attracted to each other. Organic Many colorant molecules are organic because they contain a carbon molecule. You don't have to look any further than your dinner table to find examples of organic Properties of pigments The smaller a pigment becomes the more translucent it becomes. This is true of even the most opaque pigment, titanium dioxide. Adverse Effects Iron oxides contain nickel and a large percentage of the population tested is allergic to nickel (17.9%). Tattoo needles,including surgical grade stainless steel needles, contain nickel (8.2%). So sensitivity to pigments can and does occur, even to iron oxides. The fact that organic colorants do not contain nickel is good. However, the inert iron oxides are very safe despite the presence of nickel. Organic pigments can cause severe allergic reactions and granulomas that are difficult to treat. Fortunately, this is rare. Most adverse effects come from sensitivity to antibiotic ointments applied after the permanent cosmetic procedure. IIron Oxide Colors In nature, iron oxides exist in reds, yellows, blacks, ochre, umbre and burnt umber. Synthetic iron oxides come in several shades of red, yellow and black. A pigment has both a "top tone" and an "undertone". So in addition to dealing with the undertones in Titanium Dioxide Compared to iron oxides, titanium dioxide is very opaque. However, although white in appearance, it also has undertones (DuPont) which may be blue on the light spectrum in some cases. It is often mixed with blacks, Loss of color over time a) Exposure to sunlight or UV light by Linda H. Dixon MD |
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Inorganic Pigments Iron oxides (Fe2O3 and Fe3O4) lack a carbon molecule and are therefore "inorganic". Iron oxides in nature (dirt) are often combined