What is a paint touch-up?
“Touch up” is the term most commonly used to describe the recoating of very small localized areas of a newly painted surface, in order to conceal repairs to minor damage or to cover up small surface defects, such as scuff marks, that have occurred shortly after the painting process was completed.
Unfortunately, it is not always possible to achieve an invisible touch-up. Small blemishes that may still be present will be highlighted or slight variations across the surface will be accentuated by the shadows that are cast when natural or artificial light hitting the painted surface is viewed at low or acute angles.
The same paint that was used originally should be used to minimise any colour difference. This is because small batch-to-batch variations can occur and the colour may be marginally different from that used in the original application. That’s why we always leave the left-over paint behind with the property owner which should be stored in case it is needed and not thrown away.
If touch-ups are invisible at some viewing angles but visible at other viewing angles, this indicates that they do not have the same (microscopic) surface texture as the surrounding areas of the original paintwork. Therefore application conditions used for touch-up were clearly different to those employed when then original paintwork was done.
Issues with paint touch-ups
Gloss difference: This is most evident when the paintwork is viewed at low or acute angles especially with head-on directional lighting. For example, looking along the wall towards the light in a long hallway.
The gloss difference is often related to the difference in film build. If the film thickness of the original paint was insufficient to fully seal the substrate, then it’s sheen level is likely to be flatter than normal. The extra paint that is applied during the touch-up may deliver a correct but slightly higher sheen level.
Surface texture: The difference in surface texture between the original and touch-up paint is often the major cause of touch-up problems. Different application methods and techniques can produce slightly different surface texture. The degree of the roller stipple may vary or a different appearance between roller and brush marks may be evident, especially under critical lighting conditions.
Colour difference: A colour variation between the original coat and the touch-up may present a problem, especially with deeper colours which tend to highlight any gloss or texture variations.
Opacity: The ability of paint to obliterate the background colour of the substrate is called “hiding power” or opacity. If the original coat was applied too thin or was overspread and failed to fully hide the surface below, the observed or perceived colour may not be the same. If full hiding is delivered to the repaired area by the touch-up coat, it is possible that it will stand out as having a different colour.
How does it occur?
It is not feasible to achieve a perfect match when fresh paint is applied to the same paint that has been adversely affected by in-service conditions such as weather, wear and soiling.
Touch-ups are often expected to be carried out when coatings on surfaces recently painted by a professional painter get damaged by other tradesmen working on the same site or in the same location. Often too newly painted surfaces are cleaned too soon after new paint, or with abrasive products, or too high pressure.
If this happens, the appearance of the existing painted surface has now been compromised and this can be difficult to manage.
Best practice for paint touch-ups
Firstly, the area to be touched-up needs to be clean and dry.
Achieving a touch-up that is invisible under all or most lighting and viewing conditions requires application of the same sample of paint that was originally applied to the surface.
In addition, the application equipment used (brush or roller sleeve) should be the same as those used for the original application, as should the equipment loading, the speed, pressure and direction of application.
Alternatively, combined application methods may be used, such as brushing to apply paint to the affected area followed by laying-off with a dampened but unloaded roller to provide a match to the texture of the surrounding area.
The relative ease of touching-up generally increases as the gloss level of the paint decreases. This is consistent with the general principle that flatter paints conceal surface irregularities better because they scatter the light more effectively.
Quality or invisibility of touch-ups are not a matter of paint performance but are one of skill and technique. If the same sample of paint is used, applied with the same equipment, loading, technique, pressure, direction of lay-off and preferably by the same painter, an invisible touch-up can be expected. However, it cannot be guaranteed.
In some situations, performing an effective touch-up may be too difficult since it might be necessary to repaint the entire affected surface, which is a costly and time-consuming exercise.
Why properly prepared surfaces are necessary
The easiest coating to touch-up is the one that was applied properly in the first instance. Ideal conditions include a level, clean, sealed surface with sufficient film thickness to give full opacity and colour. The general principle that flatter paints conceal surface irregularities better because they scatter the light more effectively than higher gloss levels means that the ease of touch-up is enhanced when flatter paints are employed.