Tinctorial value

Also present but not essential in permanent hair colorants are nitro dyes which dye hair without oxidation. These dyes, nitro derivatives of aminophenols and benzenediamines, impart yellow, orange, or red tones. Although they have good tinctorial value, they are not as colorfast as the oxidative dyes. They also are used in semipermanent hair colorants. 

Theoretically, the dye or chromogen can be any colored species. Of course, requirements for fastness, solubiUty, tinctorial value, ecology, and economy must be met. Most commonly used chromophores parallel those of other dye classes. Azo dyes (qv) represent the largest number with anthraquiaone and phthalocyanine making up most of the difference. Metallized azo and formazan dyes are important and have gained ia importance as a chromophore for blue dyes duriag receat years (6) (see Dyes and dye intermediates). 

Caramel is unintentionally generated in burnt carbohydrate foods (rice, oatmeal, cornmeal, etc.) and molasses (Kowkabany et al., 1953) it is the source of maple flavor and color in the concentration of maple sap to maple syrup (Stinson and Willits, 1965). In industrial manufacturing, the intended application is taken into account, because reaction conditions help determine the properties of the pyrolysate, e.g., its tinctorial value, water solubility, and alcohol stability. Tinctorial value refers to the absorbance at 560 nm of a 0.1-wt/vol% solution in a 1-cm cell. Tinctorial strength increases with acidity, temperature, and duration of heating. Caramel manufactured above pH 6.3 is biologically unstable and much below pH 3.1, it is a resin. 

The synthetic color industry dates back to the accidental discovery of the first synthetic organic dye (mauve) in 1856. Sir William Henry Perkin, in an unsuccessful attempt to synthesize quinine, succeeded in obtaining a violet dye by the oxidation of aniline. This led other scientists to experiment and discover many new colors with superior properties to the natural pigments and extracts. The use of these new and different colors in foods, drugs, and cosmetics began almost immediately because of their tinctorial value, stability, and the many shades in which they were available. 

These yellow dyestuffs, though of totally different origin, show some relationship in chemical properties, and possibly owe their tinctorial value to the same chromophor. In euxanthic acid this is a carbonyl group, which forms a ring with one oxygen atom and two benzene nuclei. 

Dye manufacturers are now considering the environmental impact of the dyes they are producing, in addition to the traditional considerations of economy, higher wet fastness, and high tinctorial value [55]. Most dyes that might potentially cause damage to the environment have been eliminated from commerce. Surprisingly, there is no environmental classification system for dyes, and weU over half are of undisclosed structure. Dyestuffs can be synthesized based on safer intermediates. 

The two major types of colorants produced today are dyestuffs and pigments. The difference between these products is evident from the definitions a dyestuff is normally a water-soluble or water-dispersible compound that, is capable of being absorbed into the substrate, whereas a pigment is normally a water-insoluble compound that requires a binder or is entrapped within the matrix of the substrate. The majority of pigments are soluble in solvents and plastics, and both dyes and pigments impart very high tinctorial value for the amount used to color a product. The major end use for dyes is in the textile, leather, and paper industries. Pigments find major uses in paint, ink, and plastic industries. 

Basic dyes were the first dye class made synthetically mauve was a basic bye. The basic dyes first were used to dye silk and wool, but they had poor fastness properties. Today basic dyes dyed on acrylics or cationic dyeable polyester have high tinctorial value they are the brightest dyes available and have unlimited color range and good fastness properties. 

A quantitative comparison of numerical values from several different sources requires some caution, because the tinctorial strength of a given pigment is largely defined by the working conditions which govern its application, as well as by the methods of determination and evaluation. 

F2 represents the K/S value at the second degree of dispersion, at which at least 90% of the ultimate tinctorial strength F is reached. 

P.Y.212 is not recommended for exterior use, but provides an excellent value for interior applications such as packaging and household durables of all types. Pigment Yellow 212 is tinctorially quite strong as metallized azos go and exhibits very good dimensional stability, making it very useful in molded items such as blow molded containers. 

P.R.48 1 is recommended especially for use in LDPE. Besides, it also affords colorations of medium tinctorial strength in PE. 0.34% pigment is required to formulate 1/3 SD colorations with 1% Ti02. Comparative values are listed for a number of other pigments. Problems may occur during vulcanization with open steam in the presence of P.R.48 1. The pigment bleeds into the wrapper (Sec. 1.8.3.6). 

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