Is There Such a Thing as Water Based Varnish?
Varnish – it’s word that has seen a lot of mileage over the centuries. It is perhaps the oldest type of coating chemistry man has kept in his artisan quiver of tools to protect a wide array of objects and surfaces.
Varnish, a resinous film former, was, and continues to be, made from various types of plant-based oils.
With a few exceptions, varnish was always made from tung or linseed oil – with castor and safflower oil showing up later on the scene.
These oils are mixed with metals and different types of spirit oils to help the resin level and dry. Often used by artists to make paints — the alchemy of blending natural compounds grew into what is now industrial paint and coatings chemistry.
It has been a long road to get to a water-based varnish.
When I started formulating in the water medium, the term “varnish” was used in the cabinet and furniture industry to specify a level of durability and visual effect.
We all know that each industry has its specific terminology to help explain products and how they function in the design and production process.
It is a simple list of products to choose from. You have…
Conversion varnish for cabinet and furniture applications…
Spar varnish for exterior marine and architectural use…
Floor-grade varnish (usually urethane) for residential and commercial use…
And, over-print varnish is commonly used in the printing industry.
Today, we see quite a few systems tagged as “water based varnish” or “emulsion varnish.”
The key is to find the right type of varnish for the specific application, and to match as close as possible the performance level of the solvent versions with the new (now, not so new..) waterborne formulas.
So, if varnish is historically oil-based, how can there be a water based, or to use a term I applied to the development of waterborne oils, “hybrids?”
Below are my qualifiers. Some folks may argue my points, but that’s why we are here, yes?
- Oil and water, by nature, do not mix. However, using some pretty cool chemistry, we can neutralize the oil resin and add water-soluble solvents…which remain in suspension! We are now on-track to become water based.
2a. Look at the solvents in the Safety Data Sheet. Certain emulsifiers are used to ‘mix’ the oil and water. These organic solvents are N-Methyl-2-Pyrrolidone (NMP), which has a bit of a toxicity issue with respect to long-term exposure to humans.
2b. DMM solvent is a modern replacement for NMP. DMM – Dipropylene Dimethyl Ether, is a safer cosolvent in terms of long-term exposure. DMM is on the “P” (propylene) side of the glycol series arrangement, and is far less toxic than the “E” (ethylene) series glycols. Ethylene glycols have an established track record of being toxic on both the short- and long-term exposure scale, and contribute to low level ozone, i.e. smog. You and your neighbors will breathe easier when P series solvents are used in the mix.
- Most water based varnish formulators will not tell you what natural oil is being used in their products – probably since they don’t think it’s important to tell you. In most cases of waterborne alkyd resin varnish they call it, “oxidized oil.” This basically means, “we are not telling you,” but the resin is based on tung, linseed, or castor oil. A good hybrid varnish has a blend of oxidized oil and a secondary acrylic blended together. Our Emtech EM8000cv is a prime example.
- Look for resin color as the film ages. If the product is being billed as an oil/water hybrid, or alkyd emulsion, then you will more then likely see a traditional straw/amber color shift in the film formation as it cures. There are a few waterborne hybrids based on tung and castor resins and they tend to color-shift less than the linseed based versions.
- The best part about water based varnish hybrids is that they are very user-friendly. When properly formulated, these blends can offer excellent brush-applied finishes and are wonderful when spray-applied. Using a hybrid varnish will keep your VOC emissions in check and they are not flammable – your insurance company and local fire official will be thrilled!
Most importantly, a well-engineered water based varnish will offer excellent durability, luster and a look/feel that matches-up with old world varnishes in restoration or new construction applications.
What are your experiences with or questions about water based varnish? Please share your thoughts or read what others are saying in the comments section below.