Microwave Dyeing | Procedure/Techniques of Microwave Dyeing | Limitations/Problems of Microwave Dyeing

Microwave Dyeing:
Microwave dyeing takes into account only the dielectric and the thermal properties. The dielectric property refers to the intrinsic electrical properties that affect the dyeing by dipolar rotation of the dye and influences the microwave field upon the dipoles. This is a terrific method of dyeing small amounts of fabric in the microwave using ‘Procion dyes'.
Microwave dyeing on fabric
Fig: Microwave dyeing on fabric (Image: instructables.com)
The aqueous solution of dye has two components which are polar, in the high frequency microwave field oscillating at 2450MHz. It influences the vibrational energy in the water molecules and the dye molecules. The heating mechanism is through ionic conduction, which is a type of resistance heating. Depending on the acceleration of the ions through the dye solution, it results in collision of dye molecules with the molecules of the fiber. The mordant helps and affects the penetration of the dye and also the depth to which the penetration takes place in the fabric. This makes microwave superior to conventional dyeing techniques.

Equipments for Microwave Dyeing:
  1. Procion Dye,
  2. Jam Jars /small Bowls / containers for mixing,
  3. Teaspoons,
  4. Urea,
  5. Soda Ash,
  6. Bicarbonate of Soda,
  7. Plastic sheeting (or surface protector),
  8. Sample fabrics such as cotton, linen, viscose,
  9. Brushes / foam applicators or spray bottle,
  10. Microwaveable container,
  11. Cling film,
  12. Metapex,
  13. Gloves, and
  14. Microwave
Microwave Dyeing Procedure:

1. Weigh the dry yarn or fibre to be dyed.

2. Thoroughly soak the fibre/yarn to be dyed (minimum 1 hour in hot water or preferably overnight in cold)

3. Shake dye container thoroughly and Measure the correct amount of dye powder for the weight (when using Landscape or Gaywool dyes, use 10 grams to 100 grams of fibre – 2 x 5 mil. Measuring spoons full - mix the dye powder in about ¾ of a cup of hot water and stir thoroughly. NB. If you are using 2 different colours to random dye, then you will need to mix 5 grams per 100 grams of fibre of each colour.

4. To random dye, place dripping fibre in a wide shallow microwave safe container such as pyrex. Spread out fibre to cover the base in one thickness only if possible.

5. Pour most of dye over one end of fibre, and other colour over the other end. Use the back of a spoon to push the fibre down into the pool of dye and spread it around, leaving a white section between the colours.

6. Cover loosely (steam must escape but you don’t want splatters) and cook on high for up to 6 minutes (dependent on power of m/w) – should have steam condensed over lid and be very hot. Remove from m/w, remove lid, turn fibre over with tongs, add the remainder of the dye (dyes) on the underside or any white spots, then add about a cup of water with tblspn white vinegar in it.

7. Recover the dish and again cook on high for 6 minutes.

8. Leave fibre in container to thoroughly cool. (Half your dye-fixing happens during the cooling down process) All dye should be absorbed into the fibre leaving just cloudy water. (Except, if you have used turquoise or bright pink, when you will have some residue in the water).

9. Rinse thoroughly in cold or tepid water until water runs clear.

10. Dry in shade – if yarn, then hanging, if fibre then flat on a table and open with fingers before it is dry.

11. To even dyeing, premix dye and add to several cups of cold water in the container to be used (enough to well cover the fibre). Stir thoroughly and then add wet fibre. Move fibre around in the dye mixture for a minute or so before cooking. Again give it 5 or 6 minutes, turn and add vinegar, then re cook as above.

Landscape and Gaywool dye all animal fibers (wool, silk, mohair, alpaca, etc.,) as well as nylon, but not other synthetics or cotton. For these you need another type of dye. The Iberia range of dyes can be used for most synthetics and natural fibres.

Limitations/Problems of Microwave Dyeing:

1. Yarn is supposed to be even colour but is patchy with a light band under the ties. Yarn is tied too tightly (should be fig. 8 ties loose enough to spread out into a flat ribbon).

2. Yarn is an uneven depth of colour, Either dye was not completely stirred in, yarn was not thoroughly wetted out or there was not enough liquid for good circulation of dye

3. Yarn is coloured but a lot of colour remains in the water. Cooking time was not long enough, or hard water was used – try adding more vinegar. Usual cause is yarn taken out of liquid before it has cooled – wastes dye!

4. Yarn is right colour but a lot of dye rinses out. Too much dye powder used for weight of fibre. NOTE; When using turquoise (Opal or Iris or Kingfisher), or Galah (bright pink) use 1/3rd less dye than usual and give at least 3 rinses.

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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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