The other two main components of your basic tool kit for traditional print retouching are water and paper.
Water
The water is to dilute the spotting dyes in order to produce the necessary shade. It’s very important to make sure to only use steam distilled or deionized water. Both types of purified water have all the dissolved minerals removed, just by different methods and for our purposes, are identical. Tap water is not a good choice for a couple of reasons. One is the chlorine that is found in most municipal water supplies, as it can interact with dye colors in peculiar and unpredictable ways. The other is the dissolved minerals. Iron, especially, can react with dyes over time and create a green cast. Other minerals like Calcium and Magnesium can leave a dusty white residue on the surface of the print as the water evaporates.
Your work should be invisible!
The water acts as a solvent for the dyes and needs to carry them into the emulsion of the paper. Once the water has done that job, it needs to evaporate completely and cleanly without any residue of any kind left on the surface of the print. You don’t want to leave any traces of your work behind for someone to see. Remember, your job is to fix things, not create more problems. If someone can look at your finished print and identify where you did your work, you need to work on your technique.
The best compliment you can receive is for the client to say that the print looks great, but they can’t tell where you did any work. (They’re not supposed to!) Sometimes, a before and after snapshot is a good idea for those clients that may have a hard time paying you for something they can’t see. What they’re paying for is all the original spots they can no longer see—they should never see the work you did that got rid of those spots.
I keep a small bottle with an eye dropper in the lid with my spotting kit and only fill it with distilled water. Try not to contaminate your water with anything. Keep it pure.

Next post, the dos and don’ts of paper.