Grayscale is a range of monochromatic shades from black to white. Therefore, a grayscale image contains only shades of gray and no color. A grey scale is used for evaluating the color shading between products and client’s approval sample or among pieces in production. Grey scaling has grades 1-5 and increases by half of grade (1, 1 1/2, 2, 2 1/2 and so on) with 5 being the highest. General speaking, most of overseas clients can accept above grade 4, while some can accept the grade 3-4.
2.0 Objectives
- · To know about Gray scale.
- · To know the types of Gray scale available in Market.
- · To know how to use Gray scale.
- · To be acquainted with the most specified Gray scale.
3.0 Description
Gray Scale
Gray scales are of mainly two types.
- Gray scale for color change.
- Gray scale for staining.
Color Change Grey Scales
These scales consist of five pairs of grey colored material numbered from 1 to 5. Number 5 has two identical greys, number 1 grey scale shows the greatest contrast, and numbers 2, 3 and 4 have intermediate contrasts. After appropriate treatment the specimen is compared with the original untreated material and any loss in color is graded with reference to the grey scale. When there is no change in the color of a test specimen it would be classified as '5'; if there is a change it is then classified with the number of the scale that shows the same contrast as that between the treated and untreated specimens.
Staining Grey Scales
A different set of grey scales is used for measuring staining. Fastness rating 5 is shown by two identical white samples (that is no staining) and rating 1 shows a white and a grey sample. The other numbers show geometrical steps of contrast between white and a series of greys. A piece 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 is given. A rating of 5 means that there is no difference between the treated and untreated material. If the result is in between any two of the contrasts on the scale, a rating of, for example, 3-4 is given. Sets of grey scales, examples of which are shown in Fig: can be supplied by the British Standards Institution.
4.0 Apparatus
- · Gray scale for color change.
- · Gray scale for staining.
To obtain a gray scale rating for staining we have to follow the following procedure.
a) Our standard should be measured by clicking on the Std:inst button in Tools and naming the standard then measuring it. Note: For staining we will measure the color of the piece of fabric before it has been treated.
b) We have to measure our batch by clicking on the Bat:instrument button. We will name the batch then measure the piece of fabric after it has been treated to see how much staining has occurred.
c) The preferred illuminant/observer conditions are D65/10°. C/2° and C/10° are also permitted by the test method. The we will go to the ‘forms’ tab the screen form then select the form ‘Gray Scale for
staining. This displays both the ISO Gray Scale Value and the AATCC Gray Scale Rating.
d) The rating on the page will tell how much staining there is. 5 being the least amount of staining and 1 being the most amount of staining.
e) The Gray scale for staining is used to rate staining from washing i.e. 2A wash test, Crock transference: AATCC Test Method 8 or ISO Test Method 105-X12.
6.0 Most Specified Gray Scale:
· ISO Grey Scale for Staining to ISO 105-A03
KCT-3062
· AATCC Grey Scale for Color Change
KCT-3063
The Gray Scale for Color Change is used to visually evaluate change in color due to colorfastness tests as described in Evaluation Procedure 1 which is included in the purchase of Gray for Color Change.
7.0 Conclusion
The experiment is easy to measure the color fastness, staining and this experiment is necessary. Grey Scales facilitate the assessment of change in color or staining, on a scale of 1-5 (with four half steps), with 5 being good and 1 being poor. So this test will be useful in our testing lab to help our job life in textile testing & quality control.
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