Running shade in knit dyeing factories is the most common and frequently happening problem which leads to a huge loss for the factory in terms of money and time.
What is running shade?
Running shade is more specifically meter to meter variation of shade in fabric. So, basically when dyes cannot migrate properly in the whole fabric thus exhaustion of dyes in fabric becomes uneven which leads to running shade or uneven dyeing.
If running shade occurs, definitely there needs re-process which causes some severe problems. Running shade also hampers production time, reduce efficiency and production output which directly converted into money.
- Shrinkage problem
- GSM problem
- Poor fabric strength and fabric quality
- Importantly fabric surface become hairier
- Not meeting the lead time
- Extra chemical and process cost etc.
Causes and remedies of running shade
So, there are some important causes which lead to running shade which is given below-
- Lack of proper combination of dyes
- Not maintaining exact dyeing process
- Lack of proper amount of salt and alkali dosing
- Lack of quality products and proper products in the bath
- Lack of proper alkali dosing
- Lack of proper pretreatment
- Not selecting good leveling agent
- Lack of awareness for water quality
- Not maintaining proper machine and material operation by the operator
- Lack of proper after treatment
Possible remedies of running shade are given below-
- First of all, the combination of dyes meaning the exhaustion and fixation curve of the dyes must be more or less similar. If there is a significant difference, it will create running shade.
- Dyeing process: Standard dyeing process should be maintained that means dosing of chemicals and dyes should be of sequence wise and maintain required temperature and pH for the specific chemical and dyes.
- The proper amount of salt and alkali needed in the liquor because if there is excess salt in the liquor then fiber affinity will be increased thus migration of dyes will be less which leads running shade.
- Select quality product and proper product for a specific purpose.
- Properly alkali dosing is important because when pH > 9.9 then dyes will not migrate only fixation will occur.
- Proper pre-treatment is badly needed to make sure fabric and liquor is free from impurities, so, a good wash is mandatory. (For better result, one may use- Persoclean STN)
- Good leveling agent should be used. On the other way, dyes will be precipitated because when there is the hardness in the water, metal gets complex bond with dyes thus improper dyes distribution in the liquor causes running shade.
- Ensure good water quality (standard less than 40ppm). If it is 40 or less than 40 then use sequestering agent and if it is <= 10ppm, sequestering agent will not be required.
- The operator should be aware of machine and material operation which means sequence of dosing amount of dosing and machine RPM.
- Lastly, proper after treatment is essential. When using softener, proper PH and softener size is must and when there is excessive unfixed dyes on the surface of fabric use proper soap to remove it perfectly.
Reference: https://www.textiletoday.com.bd/10-causes-and-remedies-of-running-shade-in-knit-dyeing/
