Vocabulary of Kantha

Here is a website that gives you the vocabulary of Kantha alongwith the basic stitches.

 

 

Types of Dyes used in Handblock Printing

The following is a brief description of the chemical dyes used in handblock printing in India:

Pigment dyes

Pigment colors are mixed with kerosene and a binder. The mixed color can be stored for a few days. The motif is printed directly on white or light-colored ground with a variety of pigment colors. Pigment colors are widely popular today because the process is simple, the mixed colors can be stored for a period of time, subtle nuances of colors are possible, and new shades evolve with the mixing of two or three colors. Also the colors are visible as one prints and do not change after processing. Colors can be tested before printing by merely applying it onto the fabric. The pigment color is made up of tiny particles, which do not dissolve entirely and hence are deposited on the cloth surface while rapid dyes and indigo sols penetrate the cloth.

Rapid fast Colors

In this process, the ground color and the color in the design are printed on white and/or light-colored grounds in one step. The dyes once mixed for printing have to be used the same day. Standard colors are black, red, orange, brown and mustard. Color variation is somewhat difficult and while printing it is not possible to gauge the quality or depth of color.

Discharge Dyes

These dyes are used if you need to print onto a dark background. Medium to dark grounds are dyed on fabric with specially prepared dyestuff . The printing colors then used on the fabric contain a chemical that interacts with the dye. This interaction simultaneously bleaches the color from the dyed ground and prints the desired color on its place. Areas can also be discharged and left white. The primary advantage of this process is that vivid and bright colors along with white can be printed on top of medium and dark grounds. 

    

Napthol

These are two sets of chemicals which upon reaction produce a third chemical essentially colorful in nature. Fabric is dyed in one and later printed with the other. The chemical reaction produces a third color. However, the biggest drawback of this process is that there are just a few chemicals available which produce colors upon reaction.

Source: http://www.aiacaonline.org/pdf/block-printing-extended-documentation.pdf 

See the images of these prints here : http://www.sashaworld.com/learn/learnframe.htm              

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Why Different types of Reactive Dyes Dye differently

Almost all the reactive dyes are built on a similar structure (Remazol Dye from Hoechst is the exception). This structure consists of (1) a chromophore (the color-bearing group), (2) a reactive group (usually a heterocyclic carbon-nitrogen ring system), and (3) a "leaving group" which is part of the carbon-nitrogen group which is generally a halogen compound (chlorine family).

Influence of Dye characteristics in reactive dyeing:

The major dye variables that affect reactive dyeing are dye chemistry, substantivity,Reactivity and solubility.

Dye chemistry:

Reactive dye has a wide variety in terms of their chemical structure. The two most important component of a reactive dye are the chromophore and the reactive group. The characteristics governed by the chromophore are color gamut, light fastness, chlorine / bleach fastness, solubility, affinity and diffusion.

The dye characteristics governed by reactive group are reactivity, dye-fiber bond stability, and efficiency of reaction with the fiber and affinity. Dyeing conditions, especially the alkali requirements and temperature as well as the use of salt also depends upon the type of reactive group.

Substantivity:

The affinity of dye for a given substrate ( textile material) is called substantivity

Substantivity more depends upon chromophore as compared to reactive system. A high substantivity may results:

• Lower dye solubility.

• High primary exhaustion.

• A high reaction rate.

• Lower diffusion coeffecient.

A low sensitivity of dyes to the variation in the processing conditions such as time, temperature, pH, material to liquor ratio may results:

• Less diffusion.

• Less migration and levelness.

• More difficult to the removal of unfixed dyes.

Substantivity is also the best measure of the ability of a dye to cover dead cotton or immature cotton fibers. Covering power is best when the substantivity is either high or very low. An increase in the dye substantivity may be affected by:

• Lower concentration of dyes.

• Higher concentration of electrolyte.

• Lower temperature.

• Higher pH upto 11.

• Lower liquor to material ratio (M:L)

Reactivity:

High dye reactivity entails a lower dyeing time and lower efficiency of fixation. To improve the efficiency of fixation by reducing dye reactivity requires a longer dyeing time and therefore less effective than an increase in substativity. Also there is wide range of temperature and pH over which the dye can be applied. Altering the pH or temperature, two dyes of intricsically different reactivity may be made to react at a similar rate can modify reactivity of dye.

Solubility:

Dyes of better solubility can diffuse easily and rapidly into the fibers, resulting in better migration and leveling. Increasing the temperature, adding urea and decreasing the use of electrolyte may affect on increase in dye solubility.

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Textile and Comfort

People have always been interested in the connection between clothing and physical well-being.Comfort has its physiological, physical-chemical and psychological components. Major components in case of textiles are Warmth, Absorbing capacity and humidity, General comfort , Cloth convenience , Skin perception , Weight and Softness. Out of these major part of comfort is directly related to the body temperature. Thus any clothing can be measured on comfort by the fact that how well it can regulate the temperature of the body. Sweating is the most effective way the human body has of cooling down. How well can a clothing provide comfort depends upon (among other factors) how well it can handle sweating.

The most effective cooling is achieved by sweat evaporating directly on the skin. Thus any clothing that behaves closest to the skin is comfortablee. The ability of a textile to transport perspiration in the form of vapour through itself and out to the exterior is generally referred to as its breathability. It is incorrect to use the terms breathability (or resistance to water vapour) and air permeability interchangeably, because low air permeability does not in itself result in lower breathability. The best example of this is modern wind- and waterproof membranes, which allow very little air to permeate in from outside (windproof), but still allow evaporated perspiration to pass through from the inside.

Fiber characteristics influence breathability the most. However contrary to popular belief,synthetic fibers are not always bad in terms of comfort. If textiles made from synthetic fibres were properly designed, they could not only offer the same heat and moisture management qualities as natural fibres but even exceed them.For example in in double faced clothings, layers of natural and synthetic fibres were combined, yet kept separate. The synthetic fibres of the "double face material" were next to the skin and conducted perspiration quickly and efficiently away from the body and into the outer cotton layer. In combination, the two materials were far more comfortable than cotton, because of the drier feeling on the skin."

There are some interesting developments in getting comfort characteristcs of fabrics they include a gradual variation in the fineness of the fibres and yarns from the inner surface of the textile to the outer surface. It improves moisture management; because the resulting narrowing of the capillaries (denier gradient) means that the moisture can be transported away from the skin really effectively. Other measeures include integrating electrical and electronic components such as heating or cooling elements. The latest battery technology and innovative methods of processing and wiring.


Sources:

http://www.innovationintextiles.com/articles/732.php

http://www.technica.net/NT/NT3/comfort_clothing.htm
 

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