Firstly, we need to know what skimming is.
Skimming is the application of a thin coat over a surface, usually to repair the surface or prepare it ahead of decoration or painting.
The surface preparation is mostly for painting, textures, and wallpapers. The coat to be used depends on the job to be done, as there are various types of coats.
Skim coating is similar to plastering in a way, though they are quite different. Skimming is a mini-plastering where the coating material has a thin layer; it is not a major part of the surface.
Can You Skim Coat Over an Already-Painted Surface?
Before answering the question, it is important to note that skimming is not a necessity for painting work. If you have a perfect wall that has a smooth surface without cracks or chips or undulation, you probably won’t need to skim coat in the first place.
You can definitely skim coat over paint, but it depends. There are things to consider and processes to follow.
As mentioned earlier, the first move is to decide if you actually need a skim coat or not.
Skim coating as a process repairs the wall by filling up dented regions and uneven surfaces by applying an appropriate compound. Let’s see how the processes work.
Steps to Skim Coat over Paint
Here are the 6 easy to follow steps that can guide you towards a perfectly skim coated surface-
1. Check the wall carefully to detect and remove peels of paint that are not balanced
Such scenarios include painted parts that are falling off, swelling parts, dipped paint, and thick layer paints appear faded. These are errors you want to skid off the surface, and you can’t afford to add your correction on a foundation of errors.
2. Use mid-grit sandpaper to scratch the surface if the paint finishing is gloss or even semi-gloss
This process may seem contradictory because roughness is introduced in the process. This form of roughness is needed to create adhesion for the skimming compound. There is a stronger grip between the surface and coat when the surface has some bare feel to it. The reactions are more direct.
3. Use a slightly wet rag to clean the surface
The things to clean off include debris, paint residues in powdered form, dust residues from the previous sanding, and bulging stains. It won’t be a bad idea to use a soft detergent and water to clean the surface of the wall if it has too much dirt.
During the process, ensure to use minimum amount of water as possible. That way, the wall is still intact in composition and strength. Be aware that the wall must be totally dry before proceeding to the next stage.
4. Use appropriate knives to apply the coating compound
This is the major process of actual skimming. Make sure the coating material is the right compound that is appropriate for the job. For instance, a coat of satin paint or eggshell goes well if you are dealing with flat sheen paint.
A knife of about 8 to 10 inches will be perfect for large areas, while a 4-inch knife does the magic for smaller regions of imperfection. This singular process is the most important; make sure you achieve a smooth solid surface by nothing adding too much or too small.
5. Allow the coating compound to dry
That will normally take between thirty minutes to one hour. When the surface is dry, it can easily be examined. Sand through the surface gently to avoid ridges of roughness.
The sanding process should be very light, then re-examine the wall. If another layer of skim coat is needed to get that finishing touch you want, apply the skim coat again. After coating, always wait for the wall to dry before using sandpaper to gentle perfect the surface.
6. Let the skim coat dry totally before the decorative process is done
This may require you to wait overnight, preferably over 8 hours. When you are sure that the wall surface is well prepared and perfectly dry, you can proceed to apply paint or wallpaper, depending on the job requirement.
It is possible to apply a skim coat over a painted surface. Just decide if skimming is actually required, as it is not a necessity.
Skimming is best done on a bare surface, so if you are applying a skim coat over a painted surface, make sure you carefully follow the required processes as highlighted above.