Of Primers, Sealers and Undercoats
So you have decided to give your home a new coat of paint and while looking for paints, you come across this terms and wonder what they do. Firstly, I would like the SMOKELESS POWDERS congratulate you on your brave decision to re-paint your house. In order to ensure your newly painted house will look as good as it can be, it is important to have an understanding of these terms. Not to worry as even professional painters are confused by these words “primers”, “sealers” and “undercoats” are used interchangeably. In this article, we will help you clear some of the doubts you may have.
What is a Primer?
We will first have to take a look at what a primer does.
A primer is a coat of paint that is applied directly to the bare substrate. Its main functions are to:
1. Provide excellent adhesion to the substrate (wall) for the new paint.
2. Provide protection to the substrate (wall) until it can be top-coated.
3. Prevent moisture reaching the substrate (wall)
4. Protect the substrate. Some wood primers have fungicide to prevent mould-growth and anti- rust properties in metal primers.
Primers are usually pigmented to allow painters to know that a wall has been primed. Also they contain a higher amount of pigment volume concentration (PVC) which results in a slightly “rough” finish after drying. This “roughness” provides for better adhesion for the subsequent coats of paint.
What is an Undercoat?
An undercoat is designed to fulfil the following roles:
1. Provide a base for the topcoat to adhere to.
2. Provide a film to prevent moisture from getting to the substrate (wall).
3. Even out small imperfection on rough surfaces.
Undercoats generally have the role of filling surface imperfections and preventing moisture. They have high pigment volume concentration (PVC) to fulfil this role. Steel primers often contain pigments such as micas and talc powder which work well to protect against moisture.
What is a Sealer?