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Cross Dyeing
Definition:
A special type of dyeing in which a yarn, fabric or even a garment made with two or more kinds of fibre having different dyeing qualities is dyed in single bath containing two different class of dyes in which each kind of dye colours only one type of fibre.
A fabric containing two or more fibre types or fibre variants is purposely dyed so that each fibre type or variant accepts a different type of dye and becomes a different colour.
Process:
Cross dyeing is accomplished in any one of the several ways but the results produce varied effects.
- First method: This method is the combination of stock dyeing or of yarn dyeing with subsequent piece dyeing.
Cross dyeing produced varied effects. For instance, either the warp or the filling yarns may be stock dyed or yarn dyed and the other set of yarns being left undyed.
The fabric is piece dyed after weaving: thus colour is given to the undyed yarn in a second dye bath, the yarns that were originally stock dyed or yarn dyed acquire some additional colouring, which blends with the piece dyed portion of the fabric.
- Second method: two separate dye baths must be used when the yarns of vegetable fibres have been combined with yarns of animal fibres in a fabric that is to be piece dyed. The fabric is dipped in both the solutions; by this method each solution will effect the fibre for which it has an affinity. This provides a colorful effect.
A mordant can be included in a single dye bath to make the dye to adhere to the fibre for which it does not have an affinity. Thus, the more expensive method of cross dyeing which requires two dye baths can be avoided or need not be used.
Another method of cross dyeing is dying of fabric composed of two different types of fibres in one dye bath containing two different dyes one for each fibre.
Merits and demerits:
- Cross dyeing is a cheaper and a quicker way to produce the same effects obtained by other dyeing methods.
- A plaid can be produced by weaving yarns of different kinds of fibre in both warp and filling directions and then dyeing the fabric in a single bath with a mixture of two kinds of dyes.
- If yarns of one kind of fibre and yarns of another fibre are used in the warp direction, vertical stripes are formed.
- The end product depends on the fibre arrangement in the fabric. It may be a check, a plaid, tweed, a stripe, a muted colour, a heather effect or some other design.
- Piece dyed fabrics are a single colour, but cross dyeing can produce multicolored fabric.
- Cross dyeing is often used to create heather effect (soft, misty colouring) strongly patterned fabrics can also be achieved, depending on the fibres used in the fabric.
Union dyeing:
Definition:
This is suitable for fabrics containing two fibres to dye them in a single uniform colour, each dye suitable for one kind of fibre in the blend.
Union dyeing is same as cross dyeing except that instead of multi-colour effects. One solid colour is produced. The dyer accomplishes this by using two or more classes of dye, each of the same colours.
Process:
- Dyeing of piece goods made of different fibres or yarns in one colour can be accomplished by this process.
- Different fibres may require different dyes to obtain the same colour; this may be done by putting the appropriate colour dye that is specific to each type of fibre in to one dye bath.
- For eg: a fabric composed of rayon and acetate can be dyed with a solid colour green by using a direct dye for the rayon, and a disperse dye of the same colour for the acetate.
Merits and demerits:
- Union dyeing process makes use of just one dye in a single bath, normally under a single set of conditions.
- Used typically to dye blends of fibres.
- It is a single step to dye a garment that comprises of a cellulosic fibre, such as cotton or rayon, with either wool, another animal fibre and nylon.
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