How to prepare a wall before painting a mural

Before you begin painting, you need to check the wall and prepare your workspace. Preparing a working surface is probably the most important and time-consuming stage of project. The preparation forms the base for the layers of glaze and varnish, and if there is a defect in the base, it will certainly be visible in the end result. Whether you are working on wall or wood, floors or metal, all need proper preparation. The basic rule of clean, sound and smooth applies to all surfaces.

Clean the wall

First, make sure that the wall is clean and not suffering from any moisture damage or structural problems, such as cracks. If you notice cracks, spackle them, but be aware that there may be an underlying structural issue that could eventually cause cracks across your mural. Examine the wall closely for signs of mold, dirt, wax, oil or grease. If you find any, clean it off thoroughly, and be aware that mold or mildew may return unless the underlying cause has been rectified. Even if the wall looks clean, it's a good idea to wash it anyway with a mild soapy solution, such as T.S.P. Cleaner (trisodium phosphate), to ensure that you are starting with as clean a slate as possible. Remove unwanted picture hooks and nails, and fill the holes with an all purpose filler or ready-mixed spakle. When dry, sand the areas and spot-prime with undercoat.


Next Step: Priming the Wall

Priming the wall is an important step in creating a mural, because the primer will help the paint stick to the wall more easily. In some cases you can apply the primer directly over the pre-existing paint on the wall, and the mural will be fine. It depends on how much elbow work you want to put into it and also on how long you want the mural to last. If you are really concerned about the longevity of the mural, then you should take some additional preparatory measures before you start painting.

To get the most permanence and best adherence of acrylic paints onto the wall, strip the existing paint off the wall by sanding it with a sanding block. To reduce the amount of dust caused by dry sanding, prepare a mild soapy solution by mixing TSP or dishwashing liquid with in a bucket of water. Dip the sanding block in the bucket of cleaning solution, squeeze out the excess water and sand the wall thoroughly. Allow the wall to dry.
After the wall has thoroughly dried, apply a coat of acrylic primer over the entire wall. Buy your acrylic primer from a home improvement / DIY store in a gallon can, rather than use an acrylic primer (such as gesso) from an art supply store. The acrylic primer from a home improvement store will get you better bang for your buck.