What is a primer and what is it for? A primer (Petrochemical or Natural) is a special paint that is applied to the desired surface before any other layers of paint to improve adhesion. In other words, it ‘primes’ the surface to receive further layers of paint. Primers can be used on a variety of different surfaces including metal, wood, drywall, and concrete. Primers are engineered to improve the filling and binding properties of the material underneath it. This can be achieved through the chemical properties of the primer, but more often is achieved through controlling the physical properties of the primer i.e. porosity, hygroscopy, and tackiness. A off the shelf big brand primer usually consists of 20–30% synthetic resin, 60–80% solvent, and 2–5% additive agent. Some primers contain polyethylene (plastic), for better durability. There are now much better natural primers which offer all the benefits, but without the nasty drawbacks and chemicals.
Have a look at this range of modern natural primers.
Why Use a Primer Before Paint?
Primers ensure that the painting surface has an ideal, uniform texture. This allows for even coatings of paint layers on top and improves adhesion to the surface. This prevents the formation of defects on the surface of the paint, such as cracking, molding, and flaking, leading to a proper, finished look.
When to Use a Primer?
In practice, a primer is often used when painting porous materials, including concrete and wood. In fact, if the material is not water-resistant and is likely to come into frequent contact with water, using a primer is a must. Even if a primer is not necessary, it can help to combat mold and moisture in other surfaces. Always prime if you’re painting a lighter color over a darker one. Eggshell and semi-gloss paints in particular require a coat of primer as they often absorb unevenly. Additionally, primers may be used when changing paint types between layers to enhance durability.
Types of Primers
There are four basic types of primers: oil-based, latex, pigmented shellac primer and of course natural primer. Each primer has use-cases where it performs the best and other cases where a different type of primer may be more suitable.
Oil based primers
Oil-based primers are a tried and tested industry standard. They are used on a wide variety of surfaces such as wood, metals, and on top of existing paint layers. They impart stain resistance properties to the surface and slow down peeling, cracking, and blistering. They fill the porous surface of various materials, especially wood, which enables a smooth coating and fewer chances of defects.
On the other hand, Oil-based primers often contain Volatile Organic Compounds (VOCs) which can be detrimental to health and the environment. They take a long time to dry and also require rigorous cleaning to be removed from brushes.
Latex based primers
The Latex primers are water-based alternatives to oil-based primers. They are more flexible and fast drying, and are less brittle than oil-based primers, making them less susceptible to peeling and cracking. They are often used to prime soft-wood, galvanized metal, and drywall. Since they are water-soluble, they can be cleaned easily. Mostly chemical based with high VOCs.
Shellac based primers
Shellac primers have good stain-blocking capabilities. They can block in stains as well as smells from the surface and prevents them from seeping through. However, they give off the most fumes and are extremely difficult to clean.
Natural Primers
Tough, modern and suitable for all surfaces. All the benefits but without the chemicals.
How to Apply Primer
Applying primer is similar to applying paint. However, knowing some basic techniques will help in laying the perfect foundation for various paint projects.
- Thoroughly clean and repair the surface on which the paint is to be applied. Wash the wall surface using a damp cloth and water. Patch any holes and wall damage (have a look at this new natural filler). Scrape off flaky paint using a putty knife.
- Use synthetic brushes, such as polyester or nylon, with a latex primer. Natural bristle brushes work best if you’re using oil-based primers.
- For interior rooms, start with the ceiling, first covering the perimeter and unpainted areas around fixtures with a paintbrush. Use a roller applicator and move in 6 feet square sections, use a series of overlapping “W” strokes from right to left, then back from left to right. Spread the primer evenly using horizontal strokes. Continue in 6 feet square sections until the entire surface is primed.
- Check the instructions on the primer can to determine how quickly you should start painting once the primer has completely dried.