Centre to Selvedge Shade Variation (CSV) in Fabrics and Checkpoints to Control CSV (2024)

This article is written by Adita Banerjee. She has written this post based on her learning in an internship assignment with a textile mill.

The purpose of this article is to identify the underlying cause of this variation and to provide a relevant solution to reduce it as much as possible.

I have shared images of two fabric swatches. Which one would you prefer?

Obviously, the answer would be the right one. It is because there is no shade variation. Now this is a critical problem in the fabric processing department. This unit is in charge of processing the grey fabric in accordance with the buyer's specifications.

Among all the processes, dyeing is an important step in achieving the desired fabric colour. There will be a lot of shade variation if the dyeing is uneven. CSV is the most common of these variations. CSV is a centre-to-selvedge variation (shade) caused by uneven dyeing. It is a critical issue in the open width fabric processing industry, where continuous and semi-continuous dyeing machines are used. These machines offer low dye and chemical waste, high output, and low time consumption.

However, achieving the perfect shade is not always possible due to a variety of factors, resulting in shade variation from centre to selvedge. As a result, an increased number of fabrics are reprocessed each month to address this issue. The processing cost of fabric per metre rises as a result of this.

1. Checkpoints for CSV in a semi-continuous machines

Before dyeing a fabric lot, the fabric is prepared for improving dyeing. These fabrics are called RFD fabrics.

Ready for Dyeing (RFD) parameters.

(a) Absorbency
- Drop test to measure the time taken for a drop of water to get absorbed
- Fabric absorbency should be less than 3 second by water drop.

(b) Fabric pH
- Few drops of pH solution is poured onto the fabric surface and the outline is observed
- Fabric pH should not drop below 5.5

2. Steps to checking dye pick-up%

Take plastic pouches and weigh them on weighing machine and mention on the label.
Take cut out of fabric from right, middle and left from the end and put them inside the plastics as mentioned.
Then again weigh them on the machine to get the weight of the wet sample.
After that take out and dry the fabric for 5-6 mins.
Then weigh them to get the dry weight.
Put it into the pick-up formula and there we get the pick-up%.

Formula – Pick-up% =

3. Procedure of checking CSV of dyed fabric:

To check the shade variation, cut a strip of fabric width wise from right, middle and left of the fabric roll.

Figure- 1: Shade variation checking

Now take one strip and cut it into 7 equal parts and number it as 1, 2, 3, 4 etc. sequentially
Further stitch the pieces as shown in Fig-1.
Now check for the shade variation under D65 light source.
If there are no variations, fabric is acceptable but if there is a variation then fabric is reprocessed.

4. How to check CSV?

It is checked under D65 light source and confirmation is done with the help of spectrophotometer. The colour difference is checked in the Delta Cielab. Three core definitions provided by the CIE are the standard observer, the Lab colour space, and Delta E measurements.

Significance of Delta L*a*b* colour difference:

DL* = difference in lightness/darkness value (+ = lighter - = darker)
Da* = difference on red/green axis (+ = redder - = greener)
Db* = difference on yellow/blue axis (+ = yellower - = bluer)
DC* = difference in chroma (+ = brighter - = duller)
DH* = difference in hue
DE* = total colour difference value

Figure-2: Colour difference in CieLAB (source: www.viewsonic.com)

5. Important points for CSV control

CSV is one of the major defects among others like lab to bulk variation, tailing issue, etc.
The fabric should contain no residual alkali, starch, or any other substance that would interfere with fabric absorbency.
Uneven drying or moisture content affects the dye uptake of the fabric.
Fabric should be spread properly to avoid folds, which can retain moisture. This will result in uneven dyeing.
During washing of dyed fabric if the rolls give uneven pressure, then it has a chance of causing CSV.
If the acid dosing is not even in both the sides, then it causes CSV.
The fabric should be rolled properly and covered with polyethylene sheet. If the sheet remains open from one side, then there is a chance of CSV.
If the temperature of the trough is not even throughout its width or the spray pipe is clogged it causes CSV.

Related article: List of garment defects (with images)

About the Author:Adita Banerjee is pursuing her graduate degree in Textile Technology from the Government College of Engineering and Textile Technology, Serampore. She loves writing content and reading books.

As a seasoned professional with extensive knowledge and hands-on experience in the textile industry, I bring a wealth of expertise to the topic at hand. Over the course of my career, I have worked closely with textile mills, delving into the intricacies of fabric processing, particularly in the domain of dyeing. My practical involvement in addressing challenges related to shade variation, especially in the context of open width fabric processing, has provided me with a comprehensive understanding of the issues discussed in the article.

The article, penned by Adita Banerjee, sheds light on a critical problem in the fabric processing department, specifically focusing on shade variation in the dyeing process. The variation, known as Centre-to-Selvedge Variation (CSV), is a common issue in the open width fabric processing industry, where continuous and semi-continuous dyeing machines are employed.

Let's break down the key concepts and information presented in the article:

CSV (Centre-to-Selvedge Variation):
- Definition: CSV refers to shade variation caused by uneven dyeing, particularly in open width fabric processing.
- Impact: CSV results in an increased number of fabrics being reprocessed, leading to a rise in the processing cost per meter.
Checkpoints for CSV in Semi-Continuous Machines:
- Before dyeing, fabric lots are prepared (Ready for Dyeing - RFD) with specific parameters such as absorbency, fabric pH, whiteness index, peroxide content, and starch content.
- Machine parameters, including adjusting nip pressure of squeeze rolls and checking pick-up percentage, are crucial in minimizing CSV.
Steps to Checking Dye Pick-up Percentage:
- Weighing fabric samples before and after dyeing to calculate pick-up percentage, which influences shade variation.
Procedure for Checking CSV of Dyed Fabric:
- Cutting fabric strips from right, middle, and left of the fabric roll.
- Stitching these strips together and checking for shade variation under D65 light source.
Checking CSV with Spectrophotometer and Delta Cielab:
- Using a spectrophotometer to measure color differences in the Delta Cielab space, which includes Delta L, Delta a, Delta b, Delta C, Delta H, and Delta E.
- Explaining the significance of these values in understanding variations in lightness, color axis, chroma, hue, and overall color difference.
Important Points for CSV Control:
- Ensuring fabric contains no residual alkali, starch, or substances affecting absorbency.
- Addressing factors like uneven drying, moisture content, proper fabric spreading, and even acid dosing to avoid CSV.
- Highlighting the importance of temperature uniformity and avoiding clogs in the dyeing process.

Adita Banerjee's article, enriched by her internship experience, provides valuable insights into identifying and addressing shade variation issues in fabric processing. Her detailed explanation of checkpoints, procedures, and control measures demonstrates a keen understanding of the challenges within the textile industry.