Dyeing Techniques

A modem dyehouse is not operable without support from laboratory work. The laboratory s tasks are among others  

Laboratory dyeing technique should simulate actual production conditions as closely as possible. It also should allow for a multiplicity of tests in a short period of time. Laboratory equipment permits dyeing of small (5 g) to larger (1 kg) textile samples. Most lab dyeing machines work batchwise, but installations for continuous operation are also available [29], 

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Traditionally, these dyes are appHed from a dyebath containing sodium sulfide. However, development in dyeing techniques and manufacture has led to the use of sodium sulfhydrate, sodium polysulfide, sodium dithionite, thiourea dioxide, and glucose as reducing agents. In the reduced state, the dyes have affinity for cellulose (qv) and are subsequendy exhausted on the substrate with common salt or sodium sulfate and fixed by oxidation. 

Mordanting of Wool A Dyeing Technique to Increase the Flame Resistance of Wool Shag Carpets," WoolFacts, Vol. 1, No. 1, Wool Bureau, Inc., New York, privately presented. Wool Bureau Technical Center, Woodbury, N.Y., 1971. 

Fig. 4. Summary of dyeing techniques related to dye reactivity and affinity characteristics.

Most vat dyes are based on the quinone stmcture and are solubilized by reduction with alkaline reducing agents such as sodium dithionite. Conversion back to the insoluble pigment is achieved by oxidation. The dyes are appHed by either exhaust or continuous dyeing techniques. In both cases the process is comprised of five stages preparation of the dispersion, reduction, dye exhaustion, oxidation, and soaping. 

Level Dyeing Techniques. It is exceptionally difficult to obtain level dyeings on acryhc, and temperature and pH control depend on fiber type and are not always adequate. Sodium sulfate in limited amounts can be used to some effect. The sulfate ions compete for the dye with the fiber SO3 sites and so retard the rate of dyeing by forming a dye complex with the ions. The effect of sodium sulfate is best with dyes having the lowest... 

Excitable tissue preparations were obtained fresh daily from live animals using the technique described by Dodd et al. (12). Protein was measured on each synapto-some preparation using the Coomassie Brilliant Blue dye technique described by Bradford (13) results were expressed as "toxin bound per mg synaptosome protein". 

Only natural dyes were known until the nineteenth century. By trial and error and probably also by chance, humans learned to extract and use a large variety of dyes of vegetable and animal origin. Dyes were extracted from the roots, trunk bark, and branches of trees, the stems, leaves, flowers, and fruits of plants, the bodies of insects and mollusks, and the eggs of insects. All the dyes obtained from natural sources are rather impure, and hence the accurate reproducibility of colors was almost impossible during antiquity. Still, many of the dyes and dyeing techniques used in antiquity were highly developed and remained in use until the discovery of the synthetic dyes in the middle of the nineteenth century (Colombo 1995 Robinson 1969). 

For comparison, the solution quantum yield was determined by the merocyanine dye technique. Acetonitrile solutions of triphenylsulfonium hexafluoroantimonate were irradiated with a 5 m. /cm2 dose. Dye solution was added and the acid content was determined by changes in dye absorption. The quantum yield for acid production was determined to be 0.8, which agrees reasonably well with the value (0.71) determined for the hexafluoroarsenate salt (8). 

Dye technique is found useful is case of the polymers that have ionic groups or these which can be transferred to ionic groups. The two kinds of Dye techniques are ... 

Dye techniques are very sensitive and are characterised by simplicity and rapidity of operation. For these only common equipment are needed. Sometimes, the Dye technique is the only suitable method for the determination of OH endgroup. 

INTESTINE Characterization of a membrane potassium ion conductance in intestinal secretory cells using whole cell patch-clamp and calcium-sensitive dye techniques, 192, 309 isolation of intestinal epithelial cells and evaluation of transport functions, 192, 324 isolation of enterocyte membranes, 192, 341 established intestinal cell lines as model systems for electrolyte transport studies, 192, 354 sodium chloride transport pathways in intestinal membrane vesicles, 192, 389 advantages and limitations of vesicles for the characterization and the kinetic analysis of transport systems, 192, 409 isolation and reconstitution of the sodium-de-pendent glucose transporter, 192, 438 calcium transport by intestinal epithelial cell basolateral membrane, 192, 448 electrical measurements in large intestine (including cecum, colon, rectum), 192, 459... 

A7b. Arvan, D. A., and Ritz, A., Measurement of serum albumin by the HABA-dye technique A study of the effect of free and conjugated bilirubin, of bile acids, and of certain drugs. Clin. Chim. Acta 26, 505-516 (1969). 

Fayez et al. have reported the colorimetric analysis of procaine and other local anesthetics by the acid-dye technique [47]. 

Dispersed Powders. The principal use of dispersed powders is in pad—dry—chemical pad—steam dyeing techniques. They are normally made from press cake by ball or bead milling to microparticle size in the presence of dispersing agents. The drying is stricdy controlled and is carried out in the presence of anticoagulants to prevent aggregation of the dispersed dye particles. 

At present the dye techniques are very useful and economical but are somewhat approximate. Advances in use of indicator dyes for measuring surface acidity and basicity may be expected to include a two-parameter measure of acid or base strength similar to the E and C equation of Drago, and the use of fluorescent indicators for colored solids. 

Development of appropriate dyeing techniques, suitable for new types of textiles and novel styling requirements. 

Indigo is available as a powder, granulate, or liquid preparation. The dyeing technique has not changed over the years and, like vat dyeing, involves the following... 

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