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The basics of prepping materials for paint PDF Print E-mail
Written by Tony D.   
Wednesday, 29 October 2008 19:57
Depending on the surface of the material you are preparing for paint there are several steps to assure good adhesion of the paint and a smooth surface. This guide covers the definition of primer and the basics for prepping several types of materials.

Primer - def. is an initial chemical coating that is very porous and has good adhesion properties with the specific surface for which it was designed and paint for which it was designed. Although primer is specifically designed to be forgiving on many surfaces it is still important that the initial surface is clean of chemicals or debris.

Prepping plastic - Plastic by it's smooth nature is not initially very adhesive to paint. Clean the surface of grease and grime. Use an alcohol based cleaner which leaves very little residue. Then wipe down with a damp rag(clean water). Dry thoroughly. Sand the part to be prepped for paint with 600 grit sandpaper till smooth to the touch. Then spray at least 2 coats of a Sandable Primer, starting with a light first coat, followed by a medium coat. Then wet sand the part with 600 grit water proof sandpaper. Clean the surface with a damp rag and dry thoroughly. It is critical that the part is dry at this stage. Sandable primer is very porous and can appear dry and still be damp. Wait at least 30 min after the part appears dry.

Here's pictures of the steps for prepping plastic:

I've started with a clear piece of plastic for this example. I've got my 600 grit sand paper ready.


Now I sand the surface using a circular pattern until all the gloss is gone and the surface looks cloudy. We have just created a smooth surface but with small scratches which the paint will adhere.
Now I clean the surface. I start with a cleaner to remove grease, but the last thing I do is wipe the surface down with water. Make sure the surface is absolutely dry before priming.
All there is left to do is spray 2 coats of primer, waiting 10min between coats, and your almost done. The only other thing is to wet-sand the primer till it is smooth and your ready for your paint.

Prepping metal - Metal that is not well cleaned is not very adhesive to paint. Clean the surface of grease and grime. Use an alcohol based cleaner which leaves very little residue. Then wipe down with a damp rag(clean water). Dry thoroughly. Sand the part to be prepped for paint with 600 grit sandpaper till smooth to the touch and down to bare metal. Then spray at least 2 coats of a Sandable Primer (that is designed specifically for metal), starting with a light first coat, followed by a medium coat. Then wet sand the part with 600 grit water proof sandpaper. Clean the surface with a damp rag and dry thoroughly. It is critical that the part is dry at this stage. Sandable primer is very porous and can appear dry and still be damp. Wait at least 30 min after the part appears dry.


These are the basics for prepping for paint. The key points to remember are the surface must be clean, smooth, and have a smooth coat of a compatible primer.
Last Updated on Wednesday, 29 October 2008 20:01