Dyeing lab is the heart of the dyeing factory. Lab dip development is done in dyeing lab. We know from the previous article, lab dip is a particular garment style, containing many shades of the fabric color which the buyer is asked have to be sent to the buyer for the approval before going for further production. Higher precision lab can aid easily to achieve the goal of the dyeing mill. Before bulk production a swatch of fabric test dyed to hit a color standard. It is a process by which buyer’s supplied swatch is matched with the varying dyes percentage in the laboratory with or without help of spectrophotometer. For doing all tests different equipment’s are used in dyeing lab. In this article I will discuss different aims of dyeing lab, working process of dyeing lab and also different types of machines those are used in dyeing lab.
Aims or Purposes of Dyeing Lab:
The main aim of dyeing lab is:
- Color match prediction
- Color difference calculation
- Determine metamerism
- Pass/Fail option
- Color fastness rating
- Cost comparison
- Strength evaluation of dyes
- Whiteness indices
- Reflectance curve and K/S curve
- Production of shade library
- Color strength
Machine Requirements in Dyeing Lab:
- CCM (Computer color matching) Software used: Color i7
- AGS Macbeth Spectralight-III
- 2 Roll laboratory padder [Vertical + Horizontal] by Mathis
- Laboratory steamer by Mathis
- Dispenser by Tecnorama
- Infrared (IR) Lab Dyeing Machine
- High Temperature Lab Dyeing Machine
- Oscillation Dyeing Machine
- Lab Jig Dyeing Machine
- GyroWash etc.
List of Tests are Done in Dyeing Lab:
Testing process in dyeing lab are divided in three classes.
- Physical Testing
- Lab Dip/Chemical Tests
- Mechanical Test
1. Physical Tests
- Fiber Diameter
- Ends per inch
- Linear Density
2. Chemical Tests
- Blend composition
- Identification of Textile Fiber
- Identification of Dyes
- Solvent Extractable matter
- Chloride Content
- Sulphate Content
- pH value of water extract
- Moisture Content
- Shrinkage to Water
- Colour Fastness Tests
3. Mechanical Test
- Tensile Strength and Elongation
- Breaking Strength
- Bursting Strength of Paper
- Tear Strength
- Elmendorff Tear Strength
- Air permeability of Paper
- Pilling Test
- Dry and Wet Rubbing (Crock Meter)
- Ether Soluble Matter
- Water Absorbency
- Lead and its compounds
- Scouring loss
Generally below tests are done in dyeing lab:
- Dimensional Stability to washing (Shrinkage)
- Colorfastness to washing
- Colorfastness to Water
- Colorfastness to Perspiration
- Colorfastness to Rubbing/Crocking
- Colorfastness to Saliva
- Colorfastness to Actual Laundering
- Print Durability
- Fabric Weight
- Thread Count
- Pilling Resistance
- pH Test
- Yarn Appearance
- Yarn Count etc.
Process flow path of continuous process in dyeing lab:
Dyeing (2 roll laboratory padder)
*For CPB process after padding it is dried in hot air oven at 60°C- 120°C for 30 min. After 2- 3 seconds of fixation soaping is done followed by drying and shade checking.
Recipe for continuous process:
- M:L = 4:1 (Color: Chemicals)
- Soda= 12gpl
- Ceragel (wetting agent) = 2 gpl
- Anti- migrating agent (MIP) = 10 gpl
- Resist salt= 5 gpl
Working process in dyeing lab:
- The standard fabric is checked in the spectrophotometer, which gives us a prediction recipe.
- According to the prediction recipe dyes are prepared in a dispenser.
- Then the caustic and chemicals are added to the dye and mixed properly.
- After that the fabric is padded through the roller.
- After dyeing the sample is dried at 120°C for 2.44 min (the temp & time depend on the fabric quality) in a e-control.
- Then the fabric is washed in soaping machine and dried by iron.
- After that the dyed fabric is compared with the standard fabric in spectra light and spectrophotometer.
Process flow path of exhaust process in dyeing lab:
Dyeing (exhaust process)
Recipe for exhaust process:
- Dye used= (Wx P)/C
Where, W= weight of fabric
C= Concentration of solution
- Glaubers salt= 50gpl
- Soda= 200 gpl
Machine used: Mathis
Machine speed: 50 rpm
Procedure for dyeing:
- Fabric is put inside the tumbler with dye and salt for first 15 minutes at room temperature.
- Then after the temperature reaches 60°c half of the soda is added and rotated for 45 minutes.
- Then again other half of soda is added and rotated for 10 mins.
- In this way it took total 70 minutes for dyeing of cotton.
After dyeing the fabric is checked for shade variation. It can be done through two ways:
- Visually in Spectralight (AGS Macbeth Spectralight-III OX-rite)
- Or in CCM using Color i7 software.
Spectralight has 6 lighting arrangement, according to sunrays received by Earth:
- Daylight 65 (D65)
- TL83 U30 (used for HNM)
- A10 (used for INCA)
You may also like: What is Shade in Textile | Fabric Shade Checking System in Textile Mill
Computer Color Matching (CCM) System:
- In computer color matching, we have to first make an attempt to quantify colors by virtue of a unique reflectance pattern that each color exhibits and then match this unique pattern by a blend of various dyes.
- The blend that gives an identical reflectance pattern is an exact match for the desired color.
- For this, we have to collect the spectral reflectance data for both the standard color and the dyes.
This data is then to be analyzed by using Kubelka-Munk equation:
- K/S= [(1-r) 2 / 2r]
- Where r is the reflectance value of samples at a given wavelength,
- K/S= color strength
The basic three things of CCM are:
- Color measurement instrument (Spectrophotometer)
- Reflectance (R %) from a mixture of dyes
- Optical model of color vision
This model gives us the L* a* b* value, from which we can calculate c*, h* and E.
L*= L Standard – L Sample
a* = a standard– a sample
b* = b standard–b sample and,
E = (L2 + a2 + b2)1/2
*If E is more than 1, then the result is declared as fail or the recipe is rejected.
*Also the color strength must be ±100, or else the recipe is rejected.
- We have dyed a lab-dip using Jakazol dyes in e-control process.
- Shade name: STD NAVY
Jakazol Yellow CE= 4.50 gpl
Jakazol Red CE= 13.50 gpl
Jakazol Blue CE= 23.00 gpl
You may also like:
- Procedure of Lab Dip Development by the Different Dyestuff in the Laboratory
- Objects and Process Sequence of Lab Dip in Dyeing Lab
- Calculation and Working Procedure of Lab Dip in Textile Industry
- What is Shade in Textile | Fabric Shade Checking System in Textile Mill
- List of Chemical Testing Equipments for Dyeing Lab
- List of Physical Testing Machines in Dyeing Lab
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.