An over-sanded drywall (also known as Sheetrock™) is often the consequence of lack of experience and will need drywall repair. However, at times, it is necessary to over sand in order to get rid of a defect. If power tools are used to sand a drywall, instead of doing it manually with sandpaper, extra caution must be taken. The thin paper that covers the drywall can be damaged in no time. When this happens, the results are never satisfactory, particularly if you end up painting over it. This is even more so if a good primer is not used as a base before painting.
Step 1 - Filling Up the Dents
This method employs the usage of a drywall compound, also known as mud, to fill the holes and dents made while sanding. This mud should have a spreadable consistency when using a joint knife, the wider the blade the better. A smoother surface may be obtained if you wet your joint knife as you apply the drywall compound. Once the imperfections are all smoothly patched, let it dry and then sand the whole area. At this point, it is recommended to work under good light so to prevent over-sanding once more. If you are not experienced using an electric sanding machine, it is highly recommended to go the conventional way, manually sanding the surface with fine grain sandpaper such as a 200 grit, or using a sanding screen. If this surface is to be painted, it is essential that a good primer be used, particularly where the repairs were made.
Step 2 - Sanding Out the Scratches
Certain scratches are easily removed by simply sanding them out with very small grain sandpaper. If this turns out not to be sufficient, then you do best cover the scratches with a thin layer of mud, let it dry and sand again. Once dry, the drywall pretty much looks uniform. However, you must distinguish the touched areas from the original drywall, in order to sand the areas. One way to identify the patched zones is by marking with a pencil. Felt tip pens are not recommended nor are ball point pens. These tend to diffuse and don’t cover easily with paint.
Step 3 - Using a Primer
It cannot be stressed enough just how important it is to use a primer once the over-sanded drywall has been repaired. If a primer is not used, the final result may be disastrous, no matter how smooth the surface may be. Since different materials have different rates of absorption, if paint is applied directly on the drywall, blotches will appear once dry. Sometimes this problem may be solved by choosing a lighter paint color to attenuate the imperfections, but in many cases, you have to re-sand and reapply a primer. For instance, as a result of over-sanding, drywall may appear fuzzy. In this case, it is recommended to sand manually, using fine grade sandpaper, so to obtain a uniform and smooth surface. Here is where a good lamp may come in handy to identify any problematic areas. Once you are satisfied with its appearance, you then apply an oil base primer and let it dry. This should take care of the fuzzy appearance.