Spray painting surface preparation.
Preparing any surface prior to spray painting is key to achieving an ideal result. Surface preparation prior to spray painting involves smoothing by filling or removing high or low spots and also providing a key for paint that will be sprayed to adhere.
Generally internal walls and ceilings can be filled using any commercially available plaster or filler or even plasterboard cements, always consult the spray paint manufacturers technical data sheet for any special preparation requirements for the paint to be sprayed.
Any areas likely to be exposed to heavy traffic and knocks or bumps may be better filled with two-part epoxy filler. Epoxy filler may also be the best material to fill any areas where higher finish is desired or external surfaces which may be exposed to weather.
Before commencing filling it is advisable to remove any loose or flaky areas and sand the entire area preferably using sandpaper or abrasive material affixed to a block which will assist in levelling evenly. Sanding the entire area also provides the required key as in fine grooves for the new spray painted coats of paint to adhere to.
Before proceeding further brush or wipe down the surface to remove all dust.
To avoid additional sanding always try to fill with a wide flat tool such as a steel trowel or wide filling knife. It will be much easier and faster if the filling the media is first pushed into the area to be filled with reasonable force to ensure any air bubbles are forced away and then wipe across the depression with a flat blade wide enough to bridge the depression which will usually leave the depression slightly under filled.
As soon as the applied filling material has set enough to sand lightly sand the area once again using a sanding block and once again after removing any remaining dust apply more filler in the same manner as the previous filling steps. Repeat these filling and a surface in levelling processes until the area has been filled and leveled to a satisfactory surface.
Usually at this stage internal walls and ceilings will be adequately prepared to begin painting. After applying the first coat of paint check for any areas that still require filling, fill these areas, sand and dust down and apply another coat which is easy if you are spray painting with a spray gun that is already set up and allow to dry before applying further coats of paint.
If the surfaces that have been prepared require a higher level of finish a handy tip may be to spray paint a very light coat of a contrasting colour across the surfaces that have been filled and allow to dry. Once dry using a good-sized sanding block continue to sand the surface and the light coat of contrasting paint you just sprayed will quickly show any high or low spots that require further attention.
Further light coats of contrasting paint can be sprayed, allowed to dry, and then sanded until the required surface has been achieved prior to spray painting.
Certain paint systems have high build primer or undercoat options which are designed to be spray painted to a higher film build and sanded to further assist in achieving a high quality level finish ready for finish spray painting. These sprayable surface preparation paint products may be referred to as spray putty, high build primer or high build undercoat.
Remember to remove all dust from the surface before spray painting any coats and the higher the level of quality preparation achieved will result in much higher quality of spray painted finish.