Stored paints can lose moisture, making it more difficult for touch-ups to match the original coat. Dilute the paint by 5 to 10 percent with water for latex-based paint or mineral spirits for oil-based paint.

Diluting paint adds moisture, which slows the wicking rate and increases the time needed for the paint to set up. You can slow down the amount of water lost through wicking by diluting the paint when using it for touchups. Reproducing the exact wicking rates each time you paint is virtually impossible, but you can try to influence it. When touching up a wall, realize that the paint will wick at a different rate than the original top coat. The rate at which wicking occurs is the controlling factor in the final look of the painted surface. Wicking refers to moisture absorbed into the substrate or surface being painted – which could be a previous layer of paint or even the drywall beneath it. Evaporation eliminates most of the moisture but generally does not affect the final touch-up job. How quickly the water leaves the film determines how good the final touch-up work can be.Įvaporation and wicking remove water from the paint.

However, in the can, the same latex paint contains only 20 to 30 percent solids for ease of application. A dried latex paint film consists mostly of pigment and binder (latex) and contains 100 percent solids.

Water leaves a paint film as it dries, according to an article by Tony Sharotta, a process engineer for Sherwin-Williams, in Cleaning & Maintenance Management magazine. Why is it so hard to make touch-ups match? Turns out, it's all about watching the paint dry. Two painters can touch up the same wall at the same time, use paint from the same can and get completely different touch-up results.

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