Place 1 tsp. of Rit dye powder or liquid into a jar. Add other colors in 1-tsp. intervals to get the color that you desire based on the Rit Color Formula Guide. Add 1/8 cup of vinegar for each teaspoon of color added to the jar if you are using the powdered Rit dye.
Add a couple of drops of alcohol and gylcerin to the jar and mix it well.
Test the color by applying it to paper. Add more alcohol and glycerin until you achieve the consistency you want. The more alcohol and glycerin you use, the thicker the ink will be.
Use the ink by dipping a fountain pen in it or soaking a dry stamp pad in it. Store the ink with the lid of the jar tightly sealed to keep it from drying out.