Burnt umbers

Burlington Biomedical Scientific Corporation, 220 Burnt umber, 28 Busulfan, 28... 

Umbers are mainly found in Cyprus. In addition to Fe203 (45-70%), they contain considerable amounts of manganese dioxide (5-20 %). In the raw state, they are deep brown to greenish brown and when calcined are dark brown with a red undertone (burnt umbers). 

In the natural state it occurs as more or less dark chestnut-brown lumps or powder, rich in moisture. It is also lixiviated and dried, before sale and then contains far less water. Burnt umber is also used, this being reddish-brown or light brown and freed from humous matter and from most of the water. 

Its examination is usually confined to the technical tests relating to fineness, covering power, etc., and to a few chemical investigations, such as those described in paragraphs 1-4, which serve mainly to distinguish natural from burnt umber. If complete analysis is required, this may be carried out by the methods already given for days (Vol. I, p. 144). 

Behaviour towards Potash.—A small quantity of the substance is boiled with about 20% caustic potash solution if the liquid becomes more or less brownish-yellow, humous substances are present (natural or dried umber) if the liquid remains colourless, these are not present (burnt umber). 

Natural umbers contain somewhat variable amounts of hygroscopic water (up to 20% or more), and the loss on ignition usually varies from 7 to 11%. The dried earth contains much less hygroscopic moisture (about 6%),but the whob of the combined water, so that the loss on Calcination is the same as with the natural earths. The burnt earth contains little hygroscopic water (usually less than 5%) and give a loss of 3-4% on calcination. In general it may be said that when an umber loses less than 5% on calcination, it is burnt —this independently of the hygroscopic water, which may be considerable even in burnt umber if this has been stored in a moist place. 

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 umber has a dark brown hue that is derived from the conversion of yellow iron oxide to red iron oxide during calcination. The Fe203 content ranges from 47-63% and Mn02 content ranges from 12-19%. Siliceous content ranges from 23-28%. 

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 . 

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

BURNT UMBER (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... 

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. 

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 siermas, and raw and burnt umbers. Syn mineral pigments and natural pigments. 

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. 

Umbers are natural brown oxide pigments with noticeable amount of manganese dioxide (5 to 20 %) in addition to Fe Oj (45 to 70 %). Raw umbers have a greenish-brown to deep brown color, but calcined umber, also known as burnt umber, has a dark reddish-brown color. 

Burnt sienna, Burnt umber, Vandyke brown Church (1901) 231-232 Salter (1869) 341... 

Burnt umber Burnt sienna Umber Euchrome, Mineral brown, Vandyke brown... 

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