What causes problems when touching up on a job site?
There are several factors that can cause problems when touching up.
Temperature: A surface temperature difference of 10 degrees or greater between the last coat and the touch up can cause the touch up to be a different color. This is most true when the temperature falls between 40 and 60 degrees. If the surface is 10 degrees warmer at touch up than it was at initial application the touch up will appear darker. If the surface is 10 degrees cooler than it was at the initial application the touch up will appear lighter. To avoid this, the touch up should be done at the same temperature as the initial application and when the ambient air temperature is more than 50 degrees.
Surface Porosity: If the surface to be painted is porous, the color and the finish can appear different especially when using eggshell or higher sheen levels. This can be avoided by using a primer first on porous surfaces. A second coat of the topcoat can also alleviate this problem also. Often, poor hiding is misdiagnosed as touch up problems. A clean white or transparent color over an un-primed or unpainted surface can result in an uneven appearance. Always prime a porous substrate, especially when using a clean white or jewel toned color.
Time Interval: Different types of paint have different final finish times. For example, alkyd based paints can take several weeks to reach their final appearance, while latex paints get to this endpoint quickly. The higher the sheen, the longer the time required to completely dry and set. To avoid this problem, allow two weeks to judge the success of a touch up.
Application Method: A noticeable touch up can occur when a different application method is used for touching up than the application method used for the initial application. For example, if the initial application is done with a sprayer or a roller and the touch up is done with a brush, there will be a noticeable difference. If the touch up is put on at a different film thickness than the initial application it will be noticeable. To avoid this problem, keep some of the original paint at the job site for touch up purposes, use the same tool for touching up (same size brush or roller nap). For an airless spray job, spray some of the material through the gun into a can to use for later touch up. When applying the touch up do not use too much paint, lightly feather out the application with a short nap cover.
If you have any questions, come on in to a Gleco Paint store and we will guide you through the process.