10 recommendations for perfect varnish films on wood

When a photo of a beautifully finished piece of furniture is posted on profile groups, the first question is what kind of varnish was used. If it was only the quality of the varnish, we would probably see only very well finished furniture everywhere. To get a really good lacquer film on wood, however, you need more than just a top quality material. Important are the preparation of the materials, the quantity applied, the working conditions, sanding and more. Each of these can make the varnish not look good, even if the varnish chosen was of the highest quality. Find out what you need to keep in mind to get a perfect varnish coat on wood in the recommendations below.

1. Wood sanding

Wood sanding is one of the most important stages of finishing. The more time and attention it is given, the better the final result will be. The purpose of the operation is to remove any scratches, prints, stains or smudges that may have appeared during the previous stages. Sometimes, in order to see them better sand by wetting the surface with water or solvent. Even if they are not visible when sanding, they will be visible when staining the wood or applying the first coat of primer. Such defects become more visible the glossier the final lacquer. Wetting will highlight them and they can be removed.

Another purpose of sanding is to make the wood grain uniform for stain-free coloring and good adhesion of the primer coat. The abrasive material cuts the fiber evenly, the surface becoming increasingly pleasant to the touch as the abrasive paper gets finer. Use wood sanding paper, the last recommended grit is 180. Using paper that is too fine may decrease adhesion of coatings next due to the fine wood dust formed that enters the fibers and blocks absorption.

2. Conditions of application

Temperature, air humidity and dust in the space where the finishing materials are applied influence the final appearance.
Temperature The optimum recommended by manufacturers for application is 18-20°C. Small deviations are acceptable because they have no visible consequences, but at larger differences the problems start. Too low a temperature does not allow the varnish to spread, it will need more thinner, resulting in a thinner film. Too high a temperature will dry the varnish too quickly and not give it enough time to set. The result will be orange-peel film. Also, the film will dry before the air and solvent get out, which will give a wrinkled appearance.

Humidity influences drying, especially if the products are water-based. The optimum humidity is 55-60%, but it should not fall below 40% or be higher than 65-70%. Too little moisture will speed drying, too much will slow it down.

Praful is the biggest enemy of lakes. During drying, dust is trapped in the film and the result will be a film that is unpleasant to the touch and surface defects. How the lake is shinierthe better the trapped dust will show through. Varnishing is not done in the same space where mechanical work is done. A slight overpressure at the application site will keep the dust at bay. This is the principle on which pressurized spray booths are built.

3. Acclimatization of materials, their preparation

It is very important that the wood and finishing materials are at room temperature. If they are stored in rooms with other temperatures, they should be brought to the finishing area and left for a few hours to acclimatize. Different temperatures will cause the film to not spread well, have air entrapped, or poor adhesion.

All finishing materials should be thoroughly mixed before use in the original packaging. Otherwise differences in viscosity may occur, gloss level or color. If using catalyzed lacquers, follow the manufacturer's recipe. Substitution with other similar materials may change the proportion.

4. The right choice of materials

Not all materials are the same. There are different types of varnishes, not just different brands. There are indoor and outdoor varnishes, varnishes that are resistant to abrasion, humidity or high temperatures, varnishes that are more or less hard. If a varnish looks great on a table or a piece of furniture, it doesn't mean that it will be suitable for floors or stairs.

If the furniture or objects you're making are for commercial use, use professional varnishes. They are more restrictive, but the results are much better. Do-it-yourself varnishes, the kind you usually find in DIY stores, are made especially for amateurs. They're easier to apply, don't require special conditions, but the results aren't spectacular either.

5. Thinner, as important as lacquer

Even if it seems hard to believe, diluent can make all the difference between a very good varnish film and a bad one. Especially with varnish, the choice of thinner is important. The varnish, as the last coat, cannot be sanded to remove any defects. It must therefore spread well, have time to dry and have the desired gloss. All this can be adjusted with thinner.

Water-based products also perform better if special thinners are used instead of water. It's more expensive, but the wood grain won't rise as much as if you thin the primer with water, and sanding will be much easier.

If varnishing wooden objects is not a hobby, my recommendation is to still use professional products for thinners. The improvement in the quality of the film will be visible.

6. To make the varnish look good, apply primer beforehand

It is possible to apply several coats of varnish in succession, but the film will not look as good as when 1-3 coats of primer are applied beforehand. The primer ensures better adhesion to the wood and can be sanded down to a flat surface on which the varnish will spread perfectly.

A primer and varnish film is thicker than a varnish film because primer usually has more resin. It's made that way to allow sanding without removing the coating altogether. Lacquers, especially professional ones are made to give film-forming properties, not thickness. They give the gloss, glossiness and resistance to abrasion, staining, rubbing, humidity.

7. Do not apply thick coats

It is always better to apply 2-3 thin coats than one thick one. This is one of the important rules of finishing. Thick coats have a tendency to crack due to the stresses that occur after drying. A coat of varnish should be no more than 150 g/m² unless the manufacturer says otherwise. Applying thick coats also runs the risk of spills on the edges or sides of the object, which are difficult to remove and look ugly.

8. Compliance with drying times

Don't rush drying, you won't get a good film. The varnish needs time to spread well and for the thinner and air to get out of the film. Rushing drying can lead to orange peel and bubbles trapped in the film. Instead of a nice, pleasant streak, you'll get a scratchy one. The film will lose its transparency, and in the case of water-based varnishes it can become opalescent.

Respecting material drying times is essential for quality results. A primer that doesn't dry well will sand hard and poorly and the varnish will not sit well on it, which can affect gloss.

9. Sanding between coats

Like sanding wood, it's very important. Sanding between coats ensures a flat surface for perfect spreading of the varnish and removal of defects occurring in the intermediate stages: dust and bubbles trapped in the film, drips, orange peel.

To sand the primer use finer sandpaper, minimum 280. When applying a very glossy topcoat, the sandpaper should be at least 400 so as not to show the fine curls that the abrasive material makes. The lack of the interior sweeping agent makes the lacquer very transparent.

10. Use of appropriate appliances

It is difficult to get a very good film if applied with a brush. Application with spray gun makes the film more spreadable and uniform. The investment in a high-performance, professional spray gun pays for itself quickly because defects are reduced and quality increases. To maintain its performance it must be constantly cleaned and maintained.

I hope you find the information useful. As always, additions are welcome. And if you have any questions or queries, please leave them below in the dedicated space. I will be sure to reply.