A coat of paint will beautify a surface, but won’t protect it. So, can you put varnish over paint to improve durability?
You can put varnish over paint, but you must sand the paint to improve the varnish adhesion. Sanding will create ridges on the finish that the sealant can penetrate and stick.
When dry, varnish forms a transparent coating that protects paint from scratches, dents, moisture, and water. The transparent coating will cover the entire surface and increase its durability.
Things To Know
Varnish is a sealant that produces a glossy clear coat that protects the surfaces underneath it. The sealant protects paint from scratches, moisture, water, and other damage.
Different types of varnishes include acrylic, spar, exterior, and polyurethane varnish. Each type has different features, but all of them will protect a surface. For instance, acrylic varnish has a colorful and moisture-resistant finish. In comparison, spar varnish has no color (clear coat) but offers a waterproof layer over surfaces.
Varnish is a tropical coat, meaning it doesn’t need to penetrate a surface to stick. Instead, its coating can stay over the top layer of wood (or paint) and dry and stick there. This sealant is compatible with all types of paint.
Sand or Not?
Since varnish isn’t a penetrating finish, sanding before applying it isn’t necessary. However, if the surface is riddled with imperfections or bumps, you must sand it to remove them. That’s because varnish is a clear coat that doesn’t hide imperfections.
You also must sand if the surface is already sealed with another sealant. Sanding will remove the glossy finish of the existing sealant, allowing varnish to stick over it.
If the paint is peeling off, it’s best to sand the paint off. If you leave the peeling paint and varnish over it, the spikes of the peeling paint will cause bubbles on the finish. Peeling paint can also cause bleed-through. However, sanding isn’t necessary if you are varnishing over water-based or fresh paint with no imperfections.
Related Read: Can You Varnish Over Old Varnish?
How To Apply Varnish Over Paint?
Applying varnish over paint isn’t difficult, but you must prep the surface properly. This guide will show you how to do that
1. Sand The Paint
While varnish is compatible with all types of paint, the sealant sticks better over water-based paint. That’s because oil-based paints have a glossy layer that will prevent good adhesion.
To sand oil-based paint before varnishing, use medium-grit sandpaper. You don’t have to sand water-based paint, unless the finish is riddled with imperfections or bumps. To sand an uneven water-based paint coating, use fine-grit sandpaper. Avoid using coarse-grit sandpaper, as it can remove the paint.
After sanding, remove dust and clean the paint coating.
2. Apply The Varnish
Once the paint coating is clean and sanded, apply varnish. To apply varnish, use a roller, paintbrush, or sprayer. If you use a sprayer, thin varnish in a ratio of 4:1, as the sealant is too thick for a sprayer.
You must apply 3-4 coats of varnish for proper coverage and protection. Wait until one coat dries before applying the next one. After applying the final coat, wait 24 hours before using the surface.
Varnish Doesn’t Change Paint Color
Most varnishes are clear coats with no paint pigments, so they won’t change the paint color. But, the glossy clear coat finish can enhance the paint shade (just a bit) and make it look different. The difference is low and won’t be noticeable.
For instance, water-based varnish tends to make the finish look brighter because its coating is clear and allows light to pass through. On the other hand, the oil-based varnish will make the paint look darker because of the high content of oils on its coating.
The number of coats also matters. If you add too many coats, the finish becomes blurry and might develop a tint after a few years.
Also, there are types of varnishes that come with a colored finish, such as acrylic varnish. Acrylic varnish is pre-mixed with acrylic paint and offers a colorful and durable finish. The durability of the mixture is gotten from the varnish, while the colored coating is gotten by the paint pigments of the acrylic paint.
Different Types of Paint:
- Latex – Latex paint is water-based, and you can varnish over it. All you need to do is clean latex paint to remove dust, and you can seal it. However, if its surface is riddled with imperfections, you must also sand it.
- Chalk – You can varnish over chalk paint because chalk paint contains little to no chemicals. Because of its simple formula, you don’t have to sand chalk paint before sealing it. Just use a damp rag to remove dust.
- Emulsion – You can varnish over emulsion paint. But, it’s better to apply water-based varnish over emulsion paint because most emulsion paints contain a high volume of water. So the paint might not be compatible with oil-based sealant. The prep before applying the sealant depends on the type of emulsion paint. For instance, a high gloss emulsion finish will need sanding, while satin and matte finishes don’t need sanding.
- Acrylic – You can apply varnish over acrylic paint, or mix them to get acrylic varnish.
- Satinwood – You can apply varnish over satinwood paint, but you must sand the paint first. That’s because satinwood is a tough, semi-gloss finish that prevents good paint adhesion.
- Matte – You can varnish over matte paint without having to sand the paint. Matte paints are water-based paints made with color, a binder, and water. As such, it has no chemicals that can repel a top coat.
- Gloss – You can varnish over gloss paint, but you must sand the gloss paint with medium-grit sandpaper. That’s because the glossy finish of the paint will prevent good paint adhesion.
Since varnish is a tropical sealant that doesn’t need to penetrate surfaces to stick, you can apply it over most paint. However, you have to sand a few types of paint (such as gloss paint) to improve the adhesion.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,