Batch To Batch shade variation of dyeing

1. Department of Textile Engineering
Project Title :
Comparison of Batch to Batch Shade
Variation Considering Parameters in Knit
Dyeing

2. PREPARED BY ©right
Name : MAZADUL HASAN SHESHIR
ID: 2010000400008
Batch: 13th Batch (Session 2009-2013)
Department: Wet Processing Technology
Email: mazadulhasan@yahoo.com (FB)
Blog: www. Textilelab.blogspot.com
Southeast University,Bangladesh
Department of Textile Engineering

3.  Shade is the depth of color percentage. Shade
is expressed in percentage of dye amount in
unit weight of fabric. Shade matching
depends on the accuracy of the man's eye. It
is a visual process for this reason same shade
may have difference comments from different
person.

4.  It is the variation of shade or depth of color (hue)
in same fabric roll or among different batches. In
dyed fabric often shade variation is found. Shade
variation may occur selvage to selvage, selvage
to center of fabric width or one end of the fabric
rolls to another end.
 Shading or shade variation is considered as one
big problem in fabric. A lot of orders are
cancelled because of the shade variation between
the batches. Though there is a tolerance is given
or set , but it is too tough to maintain the exact
same shade among all the batches. And here is
the success of a Textile Engineer.

5.  In the area of textiles, the most widely
employed method of applying colors is
dyeing. Although dyeing process affected by
many inside and outside parameters, it is a
mature technology during several thousand
years. Dyeing is still complicated today to
fully understand and control dyeing which is
more an art than a science. Besides, it is
difficult to monitor but must be dealt with to
obtain quality products by control various
parameter.

6.  Machine parameters:
 Temperature
 Time
 Pressure
 Speed (r.p.m)
 Stability of machine
 Dosing
 Liquor ratio
 Rinsing

7.  Process parameters:
 pH
 Pressure
 Time
 Temperature
 Liquor ratio
 Water Hardness
 Recipe
 Fastness

8.  Chemical parameters:
 Strength
 Purity
 Chemical composition
 Country of origin
 Environment
 Material parameters:
 Maturity of fiber
 Count Variation
 Foreign material
 Yarn uniformity
 Weave Plan
 Fabrics faults

10. Dyeing is one of the sophisticated part of the
textile production. There are so many reasons
behind the batch to batch shade variation. They
are given below:
Preparation Stage:
 Excessive Heat setting: Heat-setting has effect
on dye bond formation on synthetic fiber.
Uneven and excessive heat setting can cause
shade variation.
 Uneven pretreatment: Uneven, improper
scouring & bleaching causes shade variation.

11.  Using Chemicals of different concentration: If
concentration of input chemical is varied
from one batch to another then shade
variation is occurred.
 Improper color dosing: Improper color dosing
can cause shade variation.
 Workers’ Negligence: Due to worker’s
negligence, shade variation happens.

12.  Rope length & Cycle time: If rope length is
same but cycle time is varied from one batch to
another it may cause shade variation. For
example, if cycle time of first batch is greater
than the second batch results each portion of
the loop will not get same time for exhaustion
and fixation of dyestuff. So the dye penetration
percentage becomes higher for first batch.
 Reel speed: Reel speed changes with fabric
GSM, loads per nozzle, cycle time etc. which
has great effect on shade variation.

13.  Running time: Running time is another factor
for batch to batch shade variation. Due to the
variation of running time of different stage of
dyeing, the action of same chemical/dyes,
used in different batches also varied from one
batch to another batch. This also may cause
batch to batch shade variation.
 Fluctuation in power & temperature:
Fluctuation in power supply and temperature
also responsible for variation.

14.  Dyes lot variation: Dyes strength, reactivity etc.
properties can vary lot to lot even drum to drum
that causes shade variation.
 PH: Throughout overall dyeing process, pH has
great impact on shade variation. In reactive
dyeing, fixation pH is very much important to
achieve uniform shade. Every dyestuff appears in
different tone under different pH conditions. It
has observed that, if pH of polyester dyeing is
not within the range, shade will become
yellowish, dull etc.
 Improper neutralization: If neutralization is not
done properly, residual alkali can affect dyeing as
well as leads to shade variation.

15.  Soaping: According to the depth of shade;
amount of soap, soaping time and temperature
can change shade and can make shade variation.
 Final cationic fixing operation: Fixation operation
can cause shade variation in case of time, depth
of shade.
 Poor Lab-to-bulk Correlation: If in bulk
production same liquor ratio, recipe, chemicals,
process stages, runtime etc is not followed
according to lab, there is much more
opportunities to acquire shade variation as well
as other process faults.

16. Finishing Stage:
Not only the preparation and dyeing
operations are important, final finishing
operation also is very important to avoid batch-to-
batch variation.
 Softener quality: according to difference in
softener quality, strength, nature,
concentration, pH etc. shade variation can be
noticed during finishing.
 Unequal drying temperature: If drying
temperature is not equal, shade variation
happens.

17.  Follow the standard pretreatment procedure.
 Standard dyes and chemicals need to be
used.
 Maintain the same liquor ratio
 Try to maintain equal loop length, equal
amount of material per nozzle.
 Maintain the same dyeing cycle.
 Maintain equal dosing time, runtime
 Identical dyeing procedure should be
followed for the same depth of the Shade.

18.  Make sure that the operators add the right bulk
chemicals at the same time and temperature in
the process.
 Dyes and chemicals strength should be checked
regularly.
 The pH, hardness and sodium carbonate content
of supply water should check daily.
 Lab to bulk correlation should be maintained
properly.
 Equal finishing parameters (drying temperature,
softener treatment, squeezing pressure etc.)
should be maintained properly.