Overdyeing grey mélange gives a heathered colour that a solid dye cannot. Here is the process we run, from the soda scour to the shade check, with the full temperature and dosing curve.
At a glance
Soda + peroxideLow-alkali pretreatment
60°CDyeing temperature
80°C × 20 minAfter the salt
2 soda steps1 g/L, then the rest
Grey mélange yarn is spun from a blend of dyed or coloured fibre and undyed fibre, which gives the fabric its heathered grey look. When grey mélange is overdyed with reactive dye, only the undyed cellulose fibre takes the new colour, while the coloured fibre stays dark. The result is a heathered shade: a coloured mélange.
The route
- Soda scour: peroxide with soda ash, a lower alkali, instead of the usual caustic scour.
- Enzyme for a clean surface.
- Reactive dyeing at 60°C, with a 20-minute migration step at 80°C after the salt.
- Wash-off, soaping and softener as for cotton.
- Grey mélange already contains dyed fibre. Caustic can remove or damage that colour, so we scour with peroxide and soda: a lower alkali, never a high one. That protects the coloured fibre and keeps the grey from going lighter.
The dyeing curve
- The 20 minutes at 80°C after the salt is migration. Grey mélange fabric shows more unevenness and more running shade, because the colour pick-up is not even everywhere across the fibres. So we migrate it, the same way we treat critical shades. It is not done for the hot-brand reason; it is for the running shade.
Step by step
- At 60°C, dose the levelling agent over 3 minutes and run 3 minutes.
- Dose the colour linearly over 30 minutes and run 10 minutes.
- Dose the salt in two parts, each over 10 minutes with 10 minutes of run time.
- Check a sample.
- Steam up to 80°C at 2°C per minute and hold 20 minutes.
- Cool to 60°C.
- Dose the soda in two steps, each over 25 minutes with 10 minutes of run time: 1 g/L first, then the rest.
- Check the shade.
Common faults and buyer complaints
- The common problems on this kind of fabric are shade variation, and then running shade. These two are what we see most.
Shade variation. Keep the grey mélange from one yarn lot in one batch, and match against an approved standard from the same lot.
Running shade. The 80°C migration step after the salt, with linear colour dosing and two-step soda.
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