Can you varnish over paint
by Tomislav Najdovski on Dec 23, 2022
Another question that circulates a lot on different DIY forums that we are going to try and answer as detailed as possible is whether you can varnish over paint. As always together with a how-to guide, some general product recommendations, and tips and tricks.
But let’s start with the absolute basics and clear out what varnish actually is and when and how you use it.
Varnish is a type of coating that can be applied to wood, metal, and certain types of plastics. It serves as an impermeable layer that protects the underlying material from stains and general wear-and-tear, while also providing a glossy finish. Varnish is popular for many types of furniture, including tables, chairs, and cabinets, but it’s not the only area of use. Varnish can also be used on boats, cars, and other metal objects to prevent corrosion.
The reason for varnish being popular is because of the high durability and that, if applied right, it lasts for several years before it needs to be reapplied. Of course the quality of the varnish is also important.
Varnishing is a relatively simple process that can extend the life of your DIY-project with many many years.
So is it possible?
Short answer: yes! And it is not only possible, it is actually highly recommended since, as we mentioned above, it really does protect the underlying material. And varnish doesn’t really care what it´s protecting. The paint that is applied to the surface does endure quite a lot. All from bleaching from the sun to wear and tear from constantly being used. Getting the paint to last is a struggle for any DIY enthusiast, you simply want to keep the shine and the freshness you get when your surface is newly painted. Varnish is a really good way to keep that feeling and that look even longer. When applying varnish on the painted surface you add and establish yet another protective layer that also permits the paint to show through. Varnish is without a doubt the best clear coat product you could use since it doesn’t yellow at all over time.
Different types of paint and different characteristics
As you know there are a few different types of paint out there on the market and they all have their different characteristics, pros, and cons it is important to know them before you start applying your varnish, since they might affect the end result.
Water-based paint is really popular since it is really easy to use, dries really fast, hardly smells and none, or very few at least, toxic chemicals are in the actual paint. However, it is not very sustainable. It fades, flakes, and simply doesn’t last as long as say oil-based paint. So with that in mind, ending the woodwork with varnish on top of your water-based paint seems like a good idea. But keep in mind that mixing says an oil-based varnish with a water-based paint might not get you the result that you are looking for since, oil-based varnishes typically have a natural amber tint which leads it to become more yellow over time, and that really affects the water paint underneath it. For water-based paints, it is recommended to use acrylic-based varnishes.
Where water-based paint contains water, oil-based paint contains either natural oils, such as linseed oil synthetic alkyd that resembles natural oil. This type of paint is really durable since the paint contains a solvent thinner that actually evaporates when the paint dries and lets the resin in the paint form a hard coating that protects the pigment. The finish does last a long time and you might think that using a varnish might be a bit of overkill, but if you are not planning on changing the color of the surface for a long long time, then it is definitely recommended. And varnish over oil-based paints should also be oil-based.
How to guide
Before you start applying the varnish to your painted surface you need to make sure that the paint is completely dry. Not only dry enough to apply a second coating of paint, but it also needs to be dry all the way through. Read the instructions on the container of your paint to make sure you have given it enough time to dry.
Depending on the paint that you are trying to put varnish on top, you might need to do a bit of sanding. If the surface is already coated and sealed with another sealant you have to sand the surface a bit, in order for the new sealant, your varnish, to stick to the surface. I would definitely recommend doing manual sanding since you don’t have to actually remove any of the paint and it's much easier to apply the right kind of pressure if you leave the sanding machine unplugged for the project. If you don't know if there is another sealant already on top, simply look at the finish on the surface. if it seems really glossy, then the chance of there being another sealant is pretty high.
Make sure that the surface is clean and free from dust and other things that you don’t want on there, once the varnish is on and has dried it will be hard to remove without sanding down all of the varnish and underlying paint.
Varnish is very easy to apply and all you need is a brush in an appropriate size. Simply dip the brush in the varnish and apply it with strokes using a brush of your choice.
Now there are a few varnishes that come in a spray can and are applied using that same spray can, very much like how you would apply spray paint on the surface. Hold the can at least 18” away from the surface and use a slow and even motion to coat the entire surface in one go.
Even if you decide to apply with a brush or with a spraying device, it is very important to work in a well-ventilated room and to use appropriate safety equipment.
You will need to apply 3-4 coats of the varnish to get the best coverage and to make sure that the entire surface has an even amount of varnish. Make sure to wait until one coat is completely dry before you apply the second one. Also make sure to wait at least 24 hours after applying the final coat, before you use the surface that you have been working with.
If you are trying to decide on a varnish to use, check out our product sections on varnishes: