Color Fastness
COLOR
FASTNESS OF A DYED MATERIAL:
The outstandingly important property of a dyed material is the
fastness of the shade of color.
Color fastness refers to the resistance of color to fade or bleed of
a dyed or printed textile materials to various types of influences e.g. water,
light, rubbing, washing, perspiration etc. to which they are normally exposed
in textile manufacturing and in daily use.
STANDARDS
OF COLOR FASTNESS:
- AATCC(American Association of Textile Chemists and Colorists) technical manual:
- Describes 66 numbers of different color fastness tests.
- SDC (Society of Dyers and Colorists):
- In 1927, SDC (
- ISO(International Organization for Standardization):
- In 1947, ISO made color sub committee. ISO also grades the fastness:
- For light fastness: 1~8
- For other fastness: 1~5
- ASTM (American Society for Testing and Materials)
TYPES OF
COLOR FASTNESS:
- Color fastness to wash
- Color fastness to water
- Color fastness to rubbing/crocking
- Color fastness to perspiration
- Color fastness to light
- Color fastness to sea water
- Color fastness to saliva
- Color fastness to chlorinated water
- Color fastness to hypochlorite bleach etc
FACTORS
AFFECTING THE COLOR FASTNESS PROPERTIES:
- The molecular structure (e.g.) of a dye molecule: If the dye molecule is larger in size, it will be tightly entrapped inside the inter-polymer chain space of a fiber. Thus the fastness will be better.
- The manner in which the dye is bonded to the fibre or the physical form present.
- The amount of dye present in the fibre i.e. depth of shade. A deep shade will be less fast than a pale or light shade.
- The chemical nature of the fibre. For example, cellulosic fibres dyed with reactive or vat dyes will show good fastness properties. Protein fibres dyed with acid mordant and reactive dyes will achieve good fastness properties and so on. That is to say compatibility of dye with the fibre is very important.
- The presence of other chemicals in the material.
- The actual conditions prevailing during exposure.
ASSESSMENT
OF COLOR FASTNESS :
Color fastness
is usually assessed separately with respect to:
- Changes in the colour of the specimen being tested that is colour fading.
- Staining of undyed material which is in contact with the specimen during the test that is bleeding of colour.
GREY
SCALE:
Grey scale is an empirical scale
containing a series of pairs of neutrally colored chips, showing increasing
contrast within pairs.
It is used to assess
contrasts between the pairs of patterns visually.
Two types of grey scale -
- Color change
- Staining
Grey scales are supplied by the British
Standards Institution.
GRADE
FOR WASH & OTHER FASTNESS:
Fastness grade
|
Shade change of tested sample
|
Fastness quality
|
Staining of adjacent white sample
|
5
|
No change
|
Excellent
|
No staining
|
4
|
Slight loss in depth
|
Good
|
Very slight staining
|
3
|
Appreciable loss
|
Fair
|
Moderate
staining
|
2
|
Significant loss
|
Poor
|
Significant staining
|
1
|
Great loss in depth
|
Very poor
|
Deep staining
|
GRADE
FOR LIGHT FASTNESS:
Grade
|
Degree of fading
|
Light fastness type
|
Grade-8
|
No fading
|
Out standing
|
Grade-7
|
Very slight fading
|
Excellent
|
Grade-6
|
Slight fading
|
Very good
|
Grade-5
|
Moderate fading
|
Good
|
Grade-4
|
Appreciable fading
|
Moderate
|
Grade-3
|
Significant fading
|
Fair
|
Grade-2
|
Extensive fading
|
Poor
|
Grade-1
|
Very extensive fading
|
Very poor
|
MULTIFIBRE STRIP:
Multifibre DW
|
Multifibre TV
|
Secondary acetate
|
Triacetate
|
Bleached cotton
|
Bleached cotton
|
Polyamide
|
Polyamide
|
Polyester
|
Polyester
|
Acrylic
|
Acrylic
|
Wool
|
viscose
|
COLOR FASTNESS TO WASHING:
There are five
(5) test methods of I.S.O.-
¤ Method i,ii,iii
Same procedure
but only temperature varies.
¤ Method iv,v
Same procedure
but only time varies and used for severe purposes.
Required Apparatus and materials:
¤ SDC recommended multi-fibre fabric or recommended by ISO
¤ Grey scale for color changing
¤ Grey scale for staining
¤ Thermometer
¤ Dryer
¤ Color matching cabinet
¤ Sewing machine.
FOR TEST METHOD I, II AND III
If the first piece is
|
The other piece will be
|
Cotton
|
Wool
|
Wool
|
Cotton
|
Silk
|
Wool
|
Polyester
|
Wool or cotton
|
Acrylic
|
Wool or cotton
|
Nylon
|
Wool or Cotton
|
FOR TEST METHOD IV AND V
If the first piece is
|
The other piece will be
|
Cotton
|
Viscose
|
Viscose
|
Cotton
|
Nylon
|
Viscose or cotton
|
Polyester
|
Viscose or cotton
|
Acrylic
|
Viscose or cotton
|
Â¥ Now the dyed sample is placed between the undyed samples covering 5
× 4 cm2 area and stitched at the four edges, leaving 5x4 cm2
exposed, thus the specimen is ready for test.
Washing solution preparation:
Â¥ For ISO i, ii, iii method-5 gm/litre any of following two-
¤ ISO reference detergent
¤ High grade soap solution can be used as alternative containing-
¢
Free alkali calculated as Na2CO3
= 0.3% (maximum)
¢
Free alkali calculated as NaOH
= 0.1% (maximum)
Â¥ For ISO iv and v method-
¤ ISO reference detergent -5gm/litre
¤
Anhydrous
sodium carbonate-2 gm/litre
The reagents and material are taken in a
wash wheel and the recipes are as bellow-
Test method
|
Temp(0C)
|
Time
|
M:L Ratio
|
ISO-1
|
40º ± 2ºC
|
30 min
|
1:50
|
ISO-2
|
50º ± 2ºC
|
45min
|
1:50
|
ISO-3
|
60º ± 2ºC
|
30min
|
1:50
|
ISO-4
|
95º ± 2ºC
|
30min
|
1:50
|
ISO-5
|
95º ± 2ºC
|
4hours
|
1:50
|
After treatment:
Â¥ After washing the specimen is taken out.
Â¥ The specimen is rinsed twice in cold distilled water.
Â¥ Then it is washed in running
cold water for 10 minutes.
Â¥ The specimen is squeezed and the stitching is removed from two long
side (5 cm sides) and one short side (4 cm side) leaving another short side.
¥ It is dried at a temperature£ 60ºC.
Â¥ Then the stitch of rest side is removed.
Assessment Technique:
¥ Change in colour –
¤ The exposed part is compared with original dyed fabric with the help
of grey scale. .
¥ Staining –
¤ The undyed fabric used for covering is compared with the original
undyed fabric by grey scale for staining.
COLOR FASTNESS TO PERSPIRATION:
Â¥ Color fastness to Perspiration:
¤ The garments specially dress materials which come into contact with
the body where perspiration is heavy (like neck, under arm etc.) may suffer
from serious local discoloration.
¤ Men sweating are of two types-
¢
Acidic(around 6)
¢
alkaline(around 8)
For testing, two artificial perspiration
solutions are required which can be made as follows-
Chemicals
|
Solution A
|
Solution B
|
-histidine mono-hydrochloride
mono-hydrate
|
0.5gm
|
0.5gm
|
Sodium chloride
|
5.0gm
|
5.0gm
|
Di-sodium hydrogen orthophosphate
|
2.5gm
|
2.2gm
|
Volume in Distilled water
|
1000ml
|
1000ml
|
PH (adjust with N/10 NaOH)
|
8
|
5.8
|
Sample
preparation:
Sample
(10cm x 4cm) is taken.
¯
The
sample (10cm x 4cm) is placed and sewed between another two undyed fabric
pieces (5cm x 4cm) , leaving 5cm x 4cm exposed -
•
One will be same fabric undyed
•
Other will be a multifibre
fabric or indicated by ISO for wash fastness test method i, ii and iii
Procedure:
Perspiration
solution A or B is taken,50 times the sample weight(M:L=1:50)
wetted
well for 30mins at room temperature.
¯
The
liquor is drained
¯
The
specimen is then placed between two glass plate /Acrylic resin plate(→11.5cm x
6.0cm x 0.15cm)
¯
4.5kg(10
lb.) pressure is applied
¯
Keeping
the pressure, the assembly is kept in a Incubator for 4hrs at temperature (37O C±2OC)
After treatment:
The specimen are taken out & thoroughly
washed in water then the samples are unsewed and dried in air at temperature£60OC.
Assessment Technique:
¥ Change in colour –
¤ The exposed part is compared with original dyed fabric with the help
of grey scale. .
¥ Staining –
¤ The undyed fabric used for covering is compared with the original
undyed fabric by grey scale for staining.
COLOR FASTNESS TO WATER (ISO 105 E01)
Required reagent:
¤ Distilled water or deionised water or demineralised water.
Sample preparation:
Sample
(10cm x 4cm) is taken.
¯
The
sample (10cm x 4cm) is placed and sewed between another two undyed fabric
pieces (5cm x 4cm), leaving (5cm x 4cm) exposed -
•
One will be same fabric undyed
•
Other will be a multifibre
fabric or indicated by ISO for wash fastness test method i, ii and iii
Procedure:
Water
is taken in a 250ml beaker, 50 times the sample weight(M:L=1:50)
¯
Immersed
well for 15mins at room temperature.
¯
The
water is drained
¯
The
specimen is then placed between two glass plate/Acrylic resin plate(→11.5cm x
6.0cm x 0.15cm)
¯
4.5kg(10
lb.) pressure is applied
¯
Keeping
the pressure,the assembly is kept in Incubator for 4hrs at temperature
(37O
C±2OC)
Aftertreatment:
The specimen are taken out & thoroughly
washed in water then the samples are unsewed and dried in air at temperature£60OC.
Assessment Technique:
¥ Change in colour –
¤ The exposed part is compared with original dyed fabric with the help
of grey scale. .
¥ Staining –
¤ The undyed fabric used for covering is compared with the original
undyed fabric by grey scale for staining.
RUBBING FASTNESS
Rubbing fastness: Rubbing fastness is the resistance to
fading of dyed textiles when rubbed against a rough surface.
Â¥ Two types of rubbing test are done-
¤ Dry rub
¤ Wet rub
Apparatus:
¤ Crock meter
¤ Grey scale for staining
PROCEDURE:
- Test specimen 15cm x 5cm (may be more, it has no effect) is placed on the base of the Crock meter.
- A square of white test cloth (5cm x 5cm) which is of plain weave, desized, bleached but without finished cotton fabric (as ready to dye) is taken.
- White test cloth is attached to the finger of the crock meter.
- This finger is used in rubbing action on the sample specimen
- Rubbing is done to and fro, 10 cycles at 10seconds, i.e.20 rubs in 10s and finger pressure on the specimen is 9N.
- Rubbing test is done both for warp way and weft way.
- For dry and wet rubbing test, separate sample is used.
- For wet rubbing, the sample is dry but crocking cloth is wet. For wetting, M:L ratio is maintained not less than 1:50,water is drained after wetting and not squeezed.
Assessment Technique:
Generally degree of staining in the white
cloth is determined by grey scale.
