|
Definition: stock dyeing refers to the dyeing of fibres, or stock, before it is spun in to yarn. It is done by putting loose, unspun fibres in to large vats containing the dye solution s, which are then heated to proper temperature. From 500-3000 pounds of fibre are dyed at one time. The average being about 1000 pounds.
Method of dyeing:
Vat dyeing: This is the older and widely practices procedure is that of removing the packed fibres from the bales and then packing the stock in large vats and circulating dye liquor through the mass of fibre at elevated temperatures.
Bale dyeing: The newer method is bale dyeing, which is applicable to wool and all types of manmade fibres. This method follows, splitting the bale covering on all six sides, placing the entire bale in a specially designed designed machine, and then forcing the dye liquor through the bale of fibre. This method obviously saves time and labour costs.
Although the dye liquor is pumped through the fibre in large quantities, there may be areas where the dye does not penetrate completely. However, in subsequent blending and spinning operations, these areas are so mixed with the thoroughly dyed fibres that an overall even colour is obtained.
In stock dyeing, which is the most effective and expensive method of dyeing, the colour is well penetrated in the fibres and does not crock readily. Stock dyed fibres does not spin as readily as undyed fibre because it loses some of its flexibility, but lubricants added in the final rinsing overcomes most of this difficulty and woolens are often stock dyed.
Top dyeing: Top is the wool that has been combed to take out the short fibres, and then delivered from the combs in the rope like form about ΒΌ th inches thick.
Tops, the loose ropes of wool from the combing machine, are wound in to balls, placed on perforated spindles, and enclosed in a tank. The dye is pumped back and forth through the wool. Continuous processes on loose fibre and wool tops are also used using a pad-steam technique.
Merits and demerits:
Merits:
- Stock dyeing usually results in excellent penetration of the dye in to the fibre and evenness of colour throughout.
- Very even dyeing is possible with top dyeing method.
- The purpose of the top dyeing is also the same, the blending of tops to produce heather colour effects.
- The dye penetrates the core of the fibre will resists rubbing and therefore these dyes are likely to be more colour fast.
Demerits:
- Stock dyeing is most costly method for dyeing because the level of production is relatively low.
- There is 10-15% waste of dyed fibres through manufacturing steps.
- Stock dyeing is not used for worsted since the combing process removes short fibres. This would be a waste of money.
|
Participants