Sienna, burnt

For brown, burnt sienna, umber, sepia, and mixtures of red with black, are employed. 

Inorganic pigments are found in the earth. Iron and lead oxides provide earth colors. Copper calcium silicate and cobalt stannate provide blues. The colors burnt sienna and burnt umber come from iron oxides. Green pigments come from chromic oxide, calcinated cobalt, and zinc and aluminum oxides. Red pigments come from cadmium sulfide, cadmium selenide, and barium sulfate. All these chemical compounds come from the earth. 

Burnt siennas are reddish brown in masstone with a salmon-colored tint. The difference in hue between raw and burnt sienna results from the conversion of yellow iron oxide to red iron oxide during calcination, during which the water of crystallization is driven off. Burnt siennas typically contain 55-80% Fe203. 

Natural iron oxides are not widely used in plastics because they are coloristically inferior to their synthetic counterparts. They are chemically less pure, less chromatic, less uniform in particle size and size distribution, and 50% weaker.The burnt siennas and umbers are, however, heat stable to about 525°C. The raw siennas and umbers are less suited for plastics, as they begin to lose their water of hydration at temperatures in excess of 200°C. 

An increasing number of colored inorganic pigments are FDA-compliant. Historically, yellow iron oxide, red iron oxide, black iron oxide, zinc ferrite, burnt umber, raw and burnt sienna, channel carbon black, chromium oxide green, ultramarine blue, cobalt blue and copper chrome black have enjoyed FDA—compliant status, under 21 CFR 178.3297, Colorants for Polymers . More recently, the FDA has been successfully petitioned with regard to nickel titanium yellow, chrome titanium yellow, and cobalt green under 21 CFR 170.39, Threshold of Regulation for Substances Used in Food-Contact Articles . 

Natural reds such as persian red (found at Hormuz in the Persian Gulf), spani.sh red and burnt sienna contain ca. 50% iron oxide and represent the most important group of natural mineral pigments. Their tinting strength increases with increasing a-Fc203 content, which can amount to 95% in the purest sorts. Their utilization is mostly limited to primers, cheap ships paints and house paints (USA, Scandinavia). 

Manasse, A. and Mellini, M., Iron(hydr)oxide nanocrystals in raw and burnt sienna pigments, Eur J. Mineral., 18, 845, 2006. 

Sienna An earthy substance, brownish-yellow (raw sienna) and orange-red or reddish-brown when burnt (burnt sienna), much used as a pigment. It owes Its colors to oxides of Iron end, usually, of manganese. 

BURNT ISLAND RED or BURNT SIENNA or BURNT UMBER (1309-37-1) see iron oxide. 

BURNT SIENNA (1309-37-1) Violent reactions with powdered aluminum (thermite reaction), hydrogen peroxide, calcium disilicide (thermite reaction), ethylene oxide (may cause explosive polymerization), calcium hypochlorite, hydrazine, hydrogen trisulfide, powdered magnesium. Incompatible with powdered calcium carbide, carbon monoxide, chlorides, guanidinium perchlorate, metal acetylides. Contact with the explosive hydrazinium diperchlorate or ammonium perchlorate can be made more heat-, shock-, or friction-sensitive. Incompatible with aluminum-magnesium-zinc alloys. 

RED BURNT SIENNA BURNT UMBER CALCOTONERED COLCOTHAR COLLOIDAL FERRIC OXIDE FERRIC OXIDE INDIAN RED IRON(in) OXIDE IRON OXIDE RED IRON SESQUIOXIDE JEWELER S ROUGE MARS BROWN MARS RED NATURAL IRON OXIDES NATURAL RED OXIDE OCHRE PRUSSIAN BROWN RED IRON OXIDE RED OCHRE ROUGE RUBIGO SIENNA SYNTHETIC IRON OXIDE VENETIAN RED VITRIOL RED YELLOW OXIDE OF IRON... 

Synonyms cas 1332-37-2 burnt sienna indianred red iron oxide red oxide rouge turkey red Isoamyl Formate... 

Properties Permanent red, bulletin red, orange, Venetian red, burnt sienna, burnt umber, raw umber, raw sienna/yel. oxide, exterior It. yel., interior yel, exterior med. yel., chrome oxide, It. grn., phthalo grn., phthalo blue, violet, lamp bik. 

Synonyms Burnt sienna Cl 77491 Copperas red Ferrous ferrite Gulf red Indian red Iron mass, spent Iron oxide Iron oxide, spent Iron sponge, spent Pigment red 101 Pigment red 102 Red haematite Red iron oxide Red oxide Turkey red Definition Sienna, siderite, Persian red, Spanish red, and red ochre are natural iron oxide ores used as red pigments Empirical FejOj... 

Burnt sienna. See Iron oxide brown Iron oxide red... 

Synonyms Burnt sienna Burn umber Iron carbonate, precipitated Iron subcarbonate Pigment brown 7... 

BARIUM SULLATE PIGMENT ALUMINUM SILICATES DIATOMACEOUS SILICA MAGNESIUM SILICATES WET GROUND MICAS PURE TOLUIDINE RED TONER BARIUM SULFATE PIGMENT MAGNESIUM SILICATE PIGM. ALUMINUM SILICATE PIGM. DIATOMACEOUS SILICA RAW AND BURNT UMBER RAW AND BURNT SIENNA YELLOW IRON OXIDE SYNTHETIC FE-OXIDE INDIAN LACS PINE OIL TALL OIL... 

Pigment Insoluble, finely ground materials that give paint its properties of color and hide. Titanium dioxide is the most important pigment used to provide hiding in paint. Other pigments include anatase titanium, barium metaborate, barium sulphate, burnt sienna, burnt umber, carbon black, China clay, chromium oxide, iron oxide, lead carbonate, strontium chromate, Tuscan red, zinc oxide, zinc phosphate and zinc sulfide. 

Siennas are natural yellow iron oxide pigments with up to 50 % Fe Oj and <1 % manganese dioxide, with varying clay content. They are calcined to give burnt sienna, which is brownish-red in color. 

Earth Pigment n Class of pigments which are usually mined directly from the earth, dried, generally Calcined and ground. Typical examples are red and yellow oxides of iron, yellow ochre, raw and burnt siennas, and raw and burnt umbers. 

The technology and methods are identical to those used in the production of burnt siennas and burnt lunbers (qq.v. the iron oxide hydroxide to iron(III) oxide thermal transformation is the dominant colour-changing reaction. 

Iron oxides and hydroxides group Goethite Hematite Iron(ni) oxide, hematite type Lepidocrocite Ochre Oxford ochie Sienna Burnt sienna-. 

Burnt sienna is the calcined, oxidised equivalent of the naturally occurring earth pigment (raw) sienna q.v.). The pigment, as Church (1901) writes, has a beautiful, warm reddish hue . Heaton (1928) adds that it is a very transparent pigment with excellent colour . 

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