Years ago there was no doubt about what type of varnish to use. Virtually no professional used water-based varnish, but this situation has changed. The improvement of the product and the growing concern with the use of less polluting products have made water-based varnishes the benchmark, not only indoors, but also outdoors.
What is a water-based varnish?
A water-based varnish is one in which water is used to dissolve the resins that make up the varnish. Upon contact with the air, the water evaporates, leaving a film that covers the wood. The characteristics of the film (strength, elasticity, brightness, color, etc.) will depend on the type of varnish and resins used.
The best way to know the advantages of water-based varnishes is to compare them with other types of varnishes, more specifically with solvent-based varnishes.
Water varnish vs. Solvent varnish
Saying which type of varnish is best, whether a water-based or solvent-based one is not easy, in fact, there may not be a clear answer. It will depend on the features you are looking for.
Advantages of water-based varnishes
Low pollution and emissions index. When water is used to dissolve the resins that make up the varnish, what is released into the atmosphere when it dries is water vapor, instead of solvents, which are toxic.
Non flammable. This not only reduces risk, but also makes it easier to comply with fire regulations.
It is not self-fueling. Some synthetic varnishes, under certain conditions, may experience a phenomenon of self-combustion. Something that doesn’t happen with water-based varnishes.
Increased outdoor durability. The water-based varnish maintains its elasticity to a greater degree than synthetic or solvent-based varnishes, which crack or crack before solar radiation.
Not removed from bottom. Easy to repaint without problems removing the bottom.
More uniform color. Certain dyes perform better when dissolved in water, increasing color uniformity.
Maintains better shine and does not yellow. This is a problem that occurs with greater frequency and intensity in solvent-based varnishes.
Equipment cleaning. If we have been cautious and do not allow the varnish to dry on the equipment (brushes, gun, buckets, etc.), cleaning can be done with water. This is not only an economic saving, but also a reduction in contamination compared to a solvent varnish that requires the use of solvents.
Advantages of solvent-based varnishes
No problems with fungi or bacteria. Once opened and stored, water-based varnishes may decompose due to the attack of certain fungi or bacteria. It is generally easy to detect: it usually smells bad, there may be a layer of mold on the surface and there may also be an increase in the viscosity of the varnish.
Solvent varnishes have a Lowest price.
Higher chemical resistance. That is, they are more resistant to household products: acetone, ammonia, alcohol, wine, coffee …
Increased resistance to low temperatures, equal to or similar to 0 degrees.
Tue brighter initially.
Other disadvantages of water-based varnish
By its very nature, a water-based varnish, after application and without drying it is sensitive to water. It is recommended not to leave varnished wooden articles that have not yet dried in the open air or in the rain, especially if there is a risk of stagnation.
Some products like lime or cement can stain the water-based varnish layer is blackened.
Water-based products, not just varnish, tend to lift the wood grain during application. It is due to the hygroscopic property of the wood. For this reason, it is recommended to perform a perfect sanding before the application of water-based varnishes, mainly in woods such as oak or chestnut.
Which is better: water-based or polyurethane varnish
This is a common question, but it is poorly worded. Polyurethane is a plastic polymer that can be used to make varnishes and can dissolve in water and other solvents. This means that there is a water-based and solvent-based polyurethane varnish.
So the question should be: Which is better, water-based or solvent-based polyurethane varnish. To answer this question, you can consult the rest of the article.