Determination of Colorfastness to Rubbing(Dry&Wet) of Dyed Sample/ Crockmeter

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Introduction:

Colorfastness to rubbing means a change in color rubbed textile material. A crockmeter test cloth is used to determine whether color can be transferred from the surface of a colored textile to a specific crockmeter test cloth for rubbing in dry and wet conditions. Color is provided by pigments that are fixed to the exterior of the fibers, so rubbing fastness is of great importance to prints. Crocking is a simple way to determine fabric fastness to rubbing by examining the surface of the fabric, which is the first part of the fabric that is attacked when it is rubbed or abraded. Some rub fastness tests require more rubbing cycles than the standard 10 used in the crocking test to break down a faulty pigment binder system. It has been developed test methods and testing equipment that have an increased abrasive effect on fabric surfaces. Among them are oscillating drums, wire mesh, and emery abrasion testers. These testers are used for textiles that require high abrasion resistance, such as military fabrics, because they abrade the surface more than the crock meter. Rubbing a surface often results in color changes or frosting after rub fastness testing. In prints, frosting occurs when pigment rubs away from the fabric surface, exposing the natural fiber color beneath. It is also known as fibrillation, since individual fibers poke through the print’s surface. When the print loses its depth of shade, frosting is easily detected.

Objectives:

1. To know about fastness properties of fabric.
2. Come to learn testing procedure of rubbing fastness dry and wet condition.
3. To know how to measure rubbing fast.

Degree of Staining Grey Scale:

Staining is measured using a different gray scale. Rating 5 shows two identical white samples, while rating 1 shows a white and a gray sample. In the other numbers you can see the geometrical steps of contrast between white and a series of greys. An unstained, undyed cloth is compared to one that has been treated during the staining test, and the staining is numerically assessed.

Fastness Grade	Color staining	Fastness
Grade-5	No staining	Excellent
Grade-4	Very slight staining	Good
Grade-3	Moderate staining	Fair
Grade-2	Significant staining	Poor
Grade-1	Deep staining	Very poor

Apparatus:

1. Crockmeter.
2. Cotton rubbing cloth.
3. Gray scale for staining.
4. Light box.
5. Scissor
6. Fabric Sample.

Preparation of Specimen:

Two pieces not less than 14cm×5cm are required for dry rubbing and two for wet rubbing. One specimen of each pair shall have the long direction parallel to the warp yarns and other parallel to the weft yarns.

Test Procedure:

Colourfastness to rubbing is carried out two way. one is dry condition where cotton rubbing cloth dry condition, other way is wet condition where cotton rubbing cloth wetted by using distilled water. we will description both procedure in this article.

Dry Rubbing Test:

1. For testing, lock the test specimen onto the crockmeter’s base so that it lies flat and taut. The length or width direction of the test specimen should be parallel to the direction of rubbing.
2. The white cotton rubbing test cloth should be set to the finger of the crockmeter using the spiral spring clip. Test cloths should have a parallel weave to the direction of rubbing.
3. Now,   place the covered finger on the test sample.
4. Using the handcrank, turn the crank ten times at a rate of one turn per second. 
5. Then, to determine color transfer, remove the white rubbing test cloth from the finger, then use a gray scale to evaluate staining under the light box.
6. Same way, the warp direction is tested once, and the weft direction is tested twice.

Wet Rubbing Test:

1. Repeat procedure from 1 to 6 which is mentioned dry rubbing test procedure for another sample with the white cotton test cloth wetted in distilled water. Ensure that the rubbing test cloth will be wetted with water to 100% take up.
2. Air dries the cotton test cloth at the room temperature before evaluation.

Evaluation & Result:

Compare the contrast between the untreated and treated white rubbing cloth with the staining grey scale and rate from 1 to 5 and changing in the tested specimen with changing grey scale. This visual assessment is done in a color matching cabinet under standard lighting D65.

Staining	Warp Direction	Weft Direction	Avg. Grade
Dry	4	4-5	4-5
Wet	3	3	3

Conclusion:

In dry condition, our sample show grade 4-5. From the standard table we evaluated our tested sample is good to rubbing in dry condition. In wet condition, it show avg. grade 3 which is fair color fastness to rubbing. This experiment will help in our future life. Thanks to our teacher to help us.

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