Science Fair Projects

pH: It's to DYE for


The objective: My project was to determine the optimum pH for dyeing 100% cotton cellulose fabric using fiber reactive dyes. I believe that the high pH dye solutions will produce results with a more intense color on the fabric than the low pH dye solutions.


54 cups of dye solution were prepared. There were six colors of dye and the solutions for each color ranged from pH 5 to pH 13. The low pH solutions were made using distilled vinegar and water and the high pH solutions were made using sodium carbonate dissolved in water. The pH of each solution was tested with litmus paper before adding a measured amount of dichlorotriazine dye powder. 54 squares of 100% cotton cellulose fabric were cut and labeled, then soaked for five hours in each of the dye solutions. Then the squares were rinsed individually in tap water, then run through a washing machine using a mild detergent. They were then air dried, mounted and compared for color intensity, both qualitatively and quantitatively. It was important for me to wear latex gloves and safety goggles becuase sodium carbonate is toxic.


The optimum pH solution for dyeing 100% cellulose cotton fabric is pH 12. The higher pH solutions produced the most intense colors on the fabric, and the lower pH solutions produced uniformly less intense colors on the fabric.


My results show that the chemical reaction taking place between the dye and the fabric is enhanced at a high pH and suppressed at a low pH. The reaction that takes place is that a nucleophilic cellulosate anion attacks the carbon to which one of the chlorine atoms in the dichlorotriazine dye is attached. After the chlorine atom is displaced, a covalent bond results between the dye and the fiber.

This experiment is about studying pH as a variable in the efficacy of fiber reactive dyes.

Science Fair Project done By Michelle E. Jaconette


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