Colorimeter, cotton

Fill a cuvette about three-fourths full with distilled water and dry its outside with a tissue. To calibrate the colorimeter, place the cuvette in the colorimeter and close the lid. Turn the wavelength knob to 0%T. Press TRIGGER on the CBL and enter 0 into the calculator. Turn the wavelength knob to Red (635 nm). Press TRIGGER on the CBL and enter 100 into the calculator. Leave the colorimeter set on Red for the rest of the lab. Remove the cuvette from the colorimeter. Empty the distilled water from the cuvette. Dry the inside of the cuvette with a clean cotton swab. 

Clean the cuvette with a cotton swab and fill it about three-fourths full with the unknown dye solution. Place the cuvette in the colorimeter and close the lid. From the MAIN MENU, select COLLECT DATA (do not select SET UP PROBES as this will erase your data lists). Select MONITOR INPUT from the DATA COLLECTION MENU. Press ENTER to monitor the absorbance value of the colorimeter. After about 10-15 seconds, record the absorbance value and record it in your data table. 

Two tests were conducted to determine the influence of the pesticidal chemicals on the fabric. On the dyed fabric samples, color change due to chemical exposure was recorded both visually and with an instrumental colorimeter. On undyed cotton and wool fabrics, change in strength was determined using a tensile tester. 

Whatever the source of the change, color reduction from the characteristic white observed for newly opened cotton is likely to be an indicator of deterioration in quality. Color differences in cotton can be a source of variations in dye shades in finished fabric. Color in raw cotton is measured by the cotton colorimeter. Two characteristics are measured—the reflectance (Rd) and the yellowness (+b)—under standard illumination and density. In the U.S. system, these two values are used to determine the color grade, which was previously determined visually. 

Dry the outside of the cuvette with a tissue and place the cuvette in the colorimeter. Close the lid. After 10 to 15 seconds, press TRIGGER and enter the concentration in percent from your data table into the calculator. Remove the cuvette and pour out the solution. Rinse the inside of the cuvette with distilled water and dry it with a clean cotton swab. Repeat this step for test tubes 2 through 5. 

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