Colour Fastness & Shade Matching

COLOR FASTNESS

• Property of a pigment or dye to retain its original hue, especially without fading, running, or changing when wetted, washed, cleaned; or stored under normal conditions when exposed to light, heat, or other influences.

Factors Affecting Color Fastness

• Fiber Type
• Class of Dye Used
• Dyeing or Printing Process used
• Types of Finishing Treatments Used
• Action Of Laundering Detergents

Qualities Of The Color Evaluator

• A special individual needed who:
  • Knows why color change
  • Is skilled in colorfastness tests and knows their limitations.
  • Possesses a knowledge of dyes and pigments.
  • Has the ability to evaluate and report color changes.

Types Of Colorfastness

• Adversely affected by:
  • Washing
  • Light
  • Crocking
  • Abrasion
  • Gases in Atmosphere
  • Frosting
  • Perspiration
  • Heat

Color fastness is usually assessed separately with respect to :

1. Changes in the color of the specimen being tested , that is color change
2. Staining of undyed material which is in contact with the specimen during the test, that is due to bleeding of color

GRAY SCALE

• In order to give a more objective result a numerical assessment of each of these effects is made by comparing the changes with two sets of standard grey scales , one for color change and the other for staining
• Arrangement of Achromatic gray chips in a scale from light to dark.
• Nine pairs of non-glossy neutral grey colored chips, which illustrate the perceived color differences.
• give a corresponding fastness rating of 5, 4-5, 4, 3-4, 3, 2-3, 2, 1-2, and 1)
• #5 has two identical greys, and # 1 grey scale shows the greatest contrast, and # 2,3 and 4 have intermediate contrasts

Using A Gray Scale…

• Uses a class 5-4-3-2-1 rating system.
• Class 5 best, Class 1 worst.
• Half Rating, such as 3-4 also used.
• 5-Excellent, 4-good, 3-fair, 2-poor, 1- very poor.
• Specimens of a given hue are matched against these gray chips.
• They equate differences in lightness with differences in color.

Grey scales for staining

• A different set of grey scales is used for measuring staining
• Fastness rating is shown by two identical white chips (that is no staining) and rating 1 shows a white and dark chips. The other numbers shows geometrical steps of contrast between white and a series of greys.
• Apiece of untreated, unstained, undyed cloth is compared with the treated sample that has been in contact with the test specimen during the staining test and a numerical assessment of staining given.
• Grade of 5: no change in color, no staining
• Grade of 1: substantially different. Heavily stained

Methodology Of Testing

• Normally a multi-fibre strip of 6 fibre components used for staining test: Acetate, Cotton, Acrylic, Polyamide, Polyester and Wool.
• Usually only one specimen of fabric used.
• If material dyed or printed uniformly throughout the fabric, then specimen chosen should be representative of entire lot.

For multi –colored printed fabric, each color should be tested in order to evaluate every color.

CHROMATIC TRANSFERENCE SCALE

• Is used to evaluate fabrics resistance to crocking.
• Consists of six sets of color chips.
• Each set is graduated from light to dark with different rating.

Lighting Used For Evaluation

• When visually evaluating or comparing, standardized light source should be used.
• COLOR MATCHING BOOTH frequently used for color checking.

COLOR MATCHING BOOTH

• Contains 4 different standardized lights:
  • Daylight
  • Incandescent Light
  • Cool White Fluorescent Light
  • Ultraviolet Light
• Each used to view specimens by pushing a switch.
• Daylight used when evaluating colorfastness as color appears closer to way usually seen.

COLORFASTNESS TO WASHING

• Ability of the fabric to with stand the effect of laundering.
• Launder-o-meter is used to evaluate color fastness to washing with the help of grey scales.
• The washing of fabric results in the removal of dye, therefore staining can occur, in order to determine the staining, a white multi-fiber strip is attached to the specimen being tested for CF to washing.
• The staining effect on each fiber in the multi-fiber test fabric should be rated by using the grey scale for evaluating staining.

Condition for preparation of COLORFASTNESS TO WASHING

The Laundrometer

• Specimen placed in a metal cylinder containing water, detergent, steel balls, and chlorine.
• Rotating action of these cylinders produces the same effect as textile products being laundered.

TEST PROCEDURE

• SPECIMEN PREPERATION:
• Cut the specimen 2 x 6 inches, stapled with the multi fiber fabric.

PROCEDURE:

• Place the sample in the container along with the steel balls and detergent
• Run the machine for 45 minute
• After taking the specimen rinse it with water and soak it in acetic solution and rinse it again with water.
• Remove the excess solution
• Dry the specimen and test fabric together using an hand iron
• Remove the test fabric and compare it with the gray scale to find the fastness.

COLORFASTNESS TO LIGHT

• This refers to the ability of the fabric to withstand the sun light.
• The resistance of the sunlight depends on:
  • the intensity of the light
  • inherent properties of the fabric.
  • Season
  • altitude
  • distance from the equator.
• Weather-o-meter and Fade-o-meter most widely used instruments.
• Both this instruments use different light source and the temperature and humidity are controlled with in the machine
• Specimens placed around the light source , and remain there until the end of test.
• Then evaluated as to changes in color resulting from radiation
• Weather-o-meter is a newer and more versatile machine
• It enables specimen to be sprayed with water during the test, if desired.
• It also is able to alternate light and dark periods if continuous light exposure is not desired.
• These conditions are used in the Weather-o-meter to test fabric for such end uses as outdoor furniture, tents or rainwear.
• Both machines have either a carbon-arc lamp or a xenon-arc lamp as the light source.
• The degree of fastness required depends on end use.
• As an example, a coat material should have more color fastness than a colored dress shirt. Similarly clothes not intended to worn outside should also have certain color fastness to enable drying in sunlight.

WEATHER-O-METER

• Newer, versatile.
• It enables the specimen to be sprayed with water if needed.
• It also manipulates the light and dark period if continuous exposure is not needed.
• These make it most suitable for testing fabrics for end uses like outdoor furniture, tenting or rainwear.

Using Weather Meter

• Two testing methods are used:
• Time method
• Standard fading method

TIME METHOD

• The specimen is exposed to light for a particular amount of time.
• After the termination of time the specimen is taken out and evaluated.
• Specimen is not exposed to the same amount of light each time the test is performed.

Test Procedure – standard Fading Method

Specimen Preparation

• Cut the specimen 2.5” x 8” with the longer dimension in lengthwise.

Test Procedure

• Mount the specimen in the cardboard holder and remove the perforated strips so that half of the specimen area will be uncovered.
• Insert the cardboard holder into the metal holder and place in to the machine.
• Expose the specimen for 20 hours.
• At the end of the desired exposure time period, remove the specimen and allow it to relax in the dark at room temperature for atleast 2 hours in order to regain moisture from the air.
• Using the grey scale for evaluating colour change, determine the colour fastness rating for the test fabric.

COLOR FASTNESS TO CROCKING

• The rubbing off of colors is called as crocking.
• Fabrics with large amount of surface dyes like dark color cotton fabric tend to have poor colorfastness to crocking, pigment dyed or printed fabrics also face the same problem.
• Some time in order to increase the depth of the colors the surface dyes are not washed off which also results in crocking.

Crock Meter

• The crock meter is used to find the color fastness to crocking.
• This instrument has a finger covered by a white cotton fabric which would rub against the specimen.
• This test should be performed both as wet and dry test.
• The wet test is an severe test since moisture helps in removal of dyes

COLOR FASTNESS TO CROCKING

• Specimen Preparation
• Cut two specimens on the bias, 8”x8” and place the test specimen on the crock meter so it will be rubbed in the bias direction.
• Test Procedure
• Mount a dry, white crock test cloth over the finger section of the crock meter so that it will be rubbed in the bias direction.
• Lower the covered finger, causing the crock test cloth to slide over the coloured specimen for 10 complete cycles.
• Remove the specimen and the white crock test cloth.
• Perform a wet crocking test by the same procedure.
• Rate the crock test cloths using the colour transference chart.

COLOR FASTNESS TO PERSPIRATION.

• Perspiration can cause a fabric to change color as well as resulting in staining of adjacent material.
• The test is attempted to stimulate the actual condition. the specimen is heated for 6 hours at 38°C .
• A multifibre test fabric is placed against the specimen, the test is carried out and later evaluated for bleeding or color migration.
• After the test is completed ,the specimen is evaluated using the gray scale and the average rating is reported.

TEST PROCEDURE

SPECIMEN PREPERATION:

• Cut the specimen of 2 ¼” x 2 ¼”
• Cut the multifiber fabric to 2 x 2 inch

PROCEDURE:

• Immerse the test sample and the specimen in the acid solution for 15 min.
• With draw the fabric and remove any excess liquor
• Place the specimen in the perspiration tester
• Load the tester with 10 pounds of pressure.
• Place the loaded tester in an oven and heat it to 100*f for 6 hours
• Remove the tester from oven and allow the fabric to dry at room temperature.
• Remove specimen and test cloth and Compare with gray scale.

COLOR FASTNESS TO FROSTING

• Frosting is the change of color caused by a localized , flat abrasive action.
• Fabrics that have poor dye penetration possess poor colorfastness to frosting.
• Fabric that are cross dyed also possess poor color fastness (due to differences in the abrasion resistance) .

TESTING EQUIPMENT

• Inflated Diaphragm Abrasion Tester With Frosting Attachment
  • The specimen is held in such a way that only small portion is exposed (2 inch) to rubbing force.
  • Two abradants are used here.
• Emery Method
  • more severe test
  • used for garments that are exposed to severe abrasion resistance for a long period of time.
  • also used for fabrics that have low dye penetration.

TESTING EQUIPMENT

• Screen Wire Method
  • results in mild abrasive action.
  • a fine wire screen is used and the specimen is placed over a hard sponge material.
  • This is used for cross dyed and blended fabrics.
• In crocking test the rubbing cloth is evaluated and in this the specimen is evaluated

Difference Between Crocking Test and Frosting Test

• Crocking evaluates the appearance of the specimen
• Frosting only evaluates the rubbing cloth, not the specimen.

INFLATED DIAPHRAGM ABRASION TESTER

• The specimen is placed between the abradant and the foam.
• The table moves to and fro while the specimen is slowly rotated causing it to rub against the abradant.

SCREEN WIRE METHOD

• Place the screen and the specimen in the tester. The specimen is mounted over the foam rubber cushion.
• Apply a 2.5 pound load on the head.
• Start the tester and allow it to operate for 1200 continuous cycle.
• Stop the machine and remove the specimen.
• From this continue as previous method and find the color fastness.

COLOR FASTNESS TO GASES IN ATMOSPHERE

• The dyes in the textile material are affected to a various degree by atmospheric gases.
• The major cause for this is due to the reaction of disperse dye with ozone and oxides of nitrogen.
• The disperse dyed with acetate fabric has the maximum effect while nylon, polyester, acrylic has low effect.
• Inhibitors are used for this purpose but are not permanent.
• Darker, brighter change more dramatically.
• Typical changes: Blues turning pinkish, browns turning reddish, greens turning brownish.

Instruments Used

• GAS FADING CHAMBER:-tests the effects of oxides of nitrogen.
• OZONITER (ozone exposure chamber):-tests the effect of ozone.

General Procedure

• The specimens are placed in the gas filled chamber for a particular time along with the control fabric.
• The tests are conducted at 140*F for approximately 2-3 hours.
• The relative humidity is normally kept low due to the heating of gases.
• Gas fading termination: when blue sample turns a specific purple color.
• Ozone fading test: gray sample turns a standard brown color

TEST PROCEDURE

SPECIMEN PREPRATION:

• Cut the specimen 2 x 4 inches ,with the long direction length wise
• Cut the blue acetate control swatch 2 x 2 inches long

TEST PROCEDURE:

• Place the specimen(2x4inches)and control sample(2x2inches)in the gas fading chamber.
• Heat the chamber to about 140*f by using Bunsen burner.
• Leave the specimens in the chamber until the color changes from blue to purple.
• Change the control sample and repeat the procedure (only for ozoniter test, sample changes from grey sample turns brown.
• Using The Gray Scale Determine The Color Fastness Rating.

TEST PROCEDURE

• SPECIMEN PREPRATION:
• Cut two circular specimen of 4 ½ inches (emery method)
• Cut two circular specimen of 5 inches (screen wire method)
• PROCEDURE(EMERY METHOD):
• Place the emery paper and the specimen on the tester
• The pressure on the diaphragm is set to be 3 psi and place a 3 pound load on the head.
• Start the tester and allow it to run for 100 continuous cycles.
• Remove the specimen and vaccum it n order to remove fibre and abradant residue.
• Hand rinse the specimen by bolting it between two white cotton fabric hand iron at 300*f.
• Repeat the procedure for other specimen, using gray scale find the color fastness.

COLOR FASTNESS DUE TO HOT IRON

• The change in color of the garment due to a hot iron and dry heat can be found by Contact Heat Tester.

CONTACT HEAT TESTER

• The heat contact tester consists of 3 pairs of individually controlled heaters
• allows simultaneous testing of 3 differing temperatures in the range 100°C to 230°C.
• After the allocated time the specimens are taken out and is compared to the gray scale from which the color fastness is found out

COLOR FASTNESS TO WATER

SAMPLE PREPERATION:

• Cut the specimen and the multi fibre specimen of 6 x 6 cm and sew it together.

PROCEDURE:

• Place the specimen in a Petri dish and add distilled water to a depth of 1.5 cm
• Soak the specimen at room temperature for 15 min with occasional agitation
• After removing the excess water place the specimen in perspir-o-meter with a load of 10 pounds.
• Place the total unit in the oven at an temperature of 38*c for 18 hours
• Remove he specimen from the oven and dry it at standard atmosphere.
• Compare the sample with the gray scale to find the fastness.