Today we look at one of the newer types of common finish – waterborne or water-based finishes.

 

The Product

 

Waterborne finishes are acrylic and maybe some urethane resins.  Acrylic is a different resin than in oil, oil-based varnish, shellac, or lacquer.  Flexner calls this a “soccer ball” finish.  The (relatively) large droplets of resin are thinned with water and the surfaces are softened and get sticky with glycol ethers.  As the finish dries/cures, first the water evaporates, then the glycol ethers.  The droplets coalesce together and bond and harden as the thinner and solvent dry. 

 

Unfortunately, like many finishing products, the labels can be misleading. You will find them labeled water based polyurethane,  Clear Wood Finish, small text indicating “water based” (instead of “oil-based”), water-based lacquer,  water-based top coat,  water-borne urethane, acrylic urethane, oil-modified urethane, ultimate polyurethane, no odor poly, or just some trade name (e.g., Polycrylic, Cabothane, and Varathane Ultimate Polyurethane, the water- but not the oil-based version, Valspar Zenith Waterborne Pre-Catalyzed Lacquer).  They, as a class, are just different animals and the labels might lead you to think otherwise.  About the only clue that some of them are a waterborne finish is “cleans up with water” in the directions   See the difference here?  (Hint: look for the fine print)

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(photo credit: Popular Woodworking Magazine)

(photo credit: Deft)

 

When waterborne finishes first came out they were pretty awful.   They have matured a lot in the last few decades, and they continue to improve.  There are only a few manufacturers of the raw materials and more companies formulate them into finishes.   So they do share improvements, but don’t all behave the same and you might have to try different brands to find one you like.  Some work better for spraying and some for brushing.   Some are KCMA certified for kitchen cabinets (resist damage from common kitchen substances). 

 

Waterborne finishes may be the only choice for you if you live in an area with strict VOC laws.

Waterborne finishes have been slow to catch on in commercial work.  But some manufacturers of furniture and cabinetry are moving to it.  It’s become more common with wood floor finishes, even a version to refresh an existing finish, probably because it dries quicker and has less odor.

 

 The water does not dissolve anything, it merely thins the product and is miscible with glycol ethers.

 

Characteristics

 

Waterborne  finishes fit in characteristics between shellac, lacquer and oil-based varnishes in several attributes.

• A little harder than varnishes, not quite as hard as lacquer and shellac.  You can easily rub them out to change the sheen level, though.
• Less resistant to chemicals (solvents, water, acid, alkali) than varnishes, but more than lacquer and shellac.
• Faster drying than oil-based varnishes, but a bit slower than lacquer and shellac.
• Like some lacquers, may be pre-catalyzed.
• Bonds with fresh lower coats (“burns in” as the glycol ethers soften the surface a bit) less than lacquer and shellac, but better than varnishes.
• Like varnish, it won’t re-dissolve in its thinner, water, once cured;  unlike shellac or lacquer that will re-dissolve in their solvent.

 

While not totally “non-toxic” in the liquid state, they do have relatively low odor and are more suitable for spraying in a residence than lacquers.  They are often called EF - environmental friendly.

 

In the liquid state, these products are emulsions – things that don’t go together (resins and water) but are forced to.  Sort of like fats and water in milk.  When liquid they have a milky white appearance, but are clear when cured.  A varnish, lacquer or shellac contains a few component products and for example, you can thin varnishes or shellac in any proportion you want, or even add linseed oil to a varnish to make an oil-varnish blend.  Waterborne finishes contain up to 20 different products in a delicate balance and you can’t just add 25% more water without upsetting the balance and the product.  Some manufacturers make a special additive if you need to thin the product.  To get the product to emulsify, they add surfactants (what detergents do, break down surface tension to permit emulsification).  When they do that, it causes them to foam, so they add anti-foaming agents, and so on.

 

They lack the typical “amber” look that we have become familiar with varnishes, shellac, and lacquers.   So they can look “cool” or even blue to our eyes.   Some manufacturers add some dye to improve this, some do not.  But they don’t tell you this.  You can warm up the tone by buying a product with dye added, add a few drops of your own water-miscible dye, applying a coat or two of dewaxed shellac first, or staining the wood to begin with.  General Finishes says you can just add their water-based dye stains directly into their water-based finish products.  The clear color is an advantage if you are doing a lighter color such as a pickled finish or paint with glaze that you need to top coat.  You don’t want either of them to yellow out.

(photo credit: Minwax)  Sorry about the misleading "some polys"

(photo credit: Pinterest)

 

Waterborne finishes work best over water-based stains (dyes or pigments).  If you use an oil based stain, you may have compatibility/adhesion problems.  If you must use them, allow lots of time for the oil-based stain to dry/cure and for insurance, apply a barrier coat of shellac.  To be really sure, run a trial and to a scratch adhesion test on scrap.(1)  Sometimes, the manufacturers will tell you if they are compatible with their oil-based stains.

 

Because of the water content, these finishes will raise the grain.  Some people “pre-raise” the grain by wetting, letting surface dry, then sanding.   The grain may or may not raise again after application, so I just sand off the raised grain after the first coat.  The finish raises and stiffens the grain, making it easy to sand smooth.

 

Waterborne finishes are a bit more temperature sensitive than other finishes.  You really need to have 65 degrees or warmer, both during application and for a while thereafter.  So this might rule out garage finishing in the winter.   The product, while dry and usable soon, continues to coalesce for about 3 weeks. (So do varnishes, BTW).   So if you do run the heater in the garage or shop while applying, bring the pieces back in the house before turning the heat off.  Don’t store these finishes where they will freeze.

 

Pros:

• ·         Fast drying, 30-120 minutes or so, depending on temperature and humidity.  Can usually do 3-4 coats in a day and be done.
• ·         Very fast application when spraying
• ·         Color usually clear (an advantage when you don't want to add amber)
• ·         No noxious fumes, contain much less solvent and VOC
• ·         Non-flammable
• ·         No lingering smell so perfect for insides of boxes and cabinets
• ·         Easy clean up, no solvents needed (well, water is technically a solvent, but you know what I mean)
• ·         Good abrasion resistance

 

Cons

 

• ·         Lacks amber tone and adding depth to wood surface (when you want that)
• ·         Somewhat shorter shelf life, several years.
• ·         Temperature sensitive during curing
• ·         Raises grain first coat or two
• ·         Brands can behave differently – find one you like.

   

Application

 

I find the first coat will raise the grain a little bit.  So I sand after it’s dried and has stiffened the fibers up (“burying the grain.”).  You need to sand between the coats.  I use a P400 stearated sandpaper (3M’s 216U, AKA Sandblaster) for cutting high spots and a ScotchBrite maroon or light gray pad to overall dull. Do not use steel wool or you can end with a finish polka-dotted with rust spots.  Wipe off the dust with a rag dampened in water.

 

The finish can get “globs” from around the edge of the can or just exposure.   Stir the product well, then run through a finish strainer before use.  Like varnish, put the product in a separate container that you spray or brush from.  Stir, don’t shake, Mr. Bond.

  (photo credit: Popular Woodworking)

 

 

Avoid getting the finish on too thick.  The product’s “technical data sheet”, when available,will tell you the “wet mil” thickness (the wet finish’s thickness in 0.001”)  (2)

 

Like most finishes, there are three ways to apply waterborne finish.  

 

Spray

 

Spray on coats overlapping half as you go.   I will say, these finishes can look terrible right after application.  Don’t be tempted to keep adding more.  “Spray and go away.”   They will flow out well and look great in a few minutes.   You can leave the finish in the spray gun if you are going to add another coat in an hour or so.  But do clean your gun, including disassembly when done for the day.  Spraying is the way I like to do it, with an HVLP sprayer.

 

Brush

 

Condition your brush before using by wetting with water and shaking out the excess.  Since the product is fast-drying, don’t keep going over the same spot or the finish tends to “tear” when partially cured.  Get it on and get off it. 

 

There are several options with brushes.  To use a bristle brush, choose a synthetic bristle as natural bristles get flabby when wet.   Some people put the toe of a nylon stocking over the bristles to get it to flow on well.  Put on in long strokes like you would any of the other finishes.

 

You can also use a disposable foam brush.   These tend to reduce some of the foaming.

 

Another option is a painter’s pad like used for edge trimming.   This works like a short-bristled, wide and long brush with a foam reservoir.

 

Clean up any of these with soap and water after use, rinse well, and let dry.

 

Cloth

 

There are some waterborne finishes that are made for wiping but generally used in touch up business as they don’t build very fast.   Mohawk’s “Finish Up” is one example.  Some people say you can thin 10% with water and wipe.  Might work, might not, depending on brand.  Might upset the chemistry balance.

 

Fixing Goofs

 

Drips and runs -  Let them harden, sand or scrape level and apply another application.  Apply lighter, even coats.

 

Brush marks – sand out and apply thinner coats, apply in a pass or two, then don’t keep brushing the same spots.  Or change brands as the one you are using might work better for spraying.

 

Bubbles - don’t shake the finish, stir it.

 

Globs of finish in the surface or on your brush or gun– strain the finish before applying.

 

In summary, I will say that when I was doing stripping and refinishing as part of my business, I used waterborne finishes in all cases of clear finishes.  And in all but one case (because of its size only), I sprayed, even on-site kitchen cabinets and doors.  A friend who runs a custom furniture shop also uses them to avoid issues with EPA, insurance, and OSHA.

 

 

Further reading:
 

(1)    Scratch adhesion test  - https://en.wikipedia.org/wiki/Paint_adhesion_testing#Test_Method_B

(2)    Wet mil gauge https://www.youtube.com/watch?v=Ch11gPhqiG8

 

https://www.canadianwoodworking.com/tipstechniques/waterborne-finishes

http://www.rockler.com/how-to/waterborne-wood-finish-basics/

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0ahUKEwjT7a-K26zVAhXL4SYKHYNjBZUQFghPMAY&url=http%3A%2F%2Fwww.ronbryze.com%2Fwaterborne%2FAllAboutWaterborne_C.pdf&usg=AFQjCNFV-2hHHrQuH1jiLcUZy_rFPvgzfw

Edited August 1, 20178 yr by kmealy

Thanks! Great information!

Good stuff, there. I remember my first encounter with a waterborne being Crystalac, and I applied it to a piece of oak that was to be part of a doorway arch. I seldom stain wood, and with just the Crystalac the board looked awful. It did indeed have a slight blueish caste to it. Since then I've used Target Coatings and GF products and haven't seen that problem....but that blue color left ,me with a bad taste in my mouth for quite a few years.

Came across the news feed today.  Though oriented toward production, useful information.

 

I do agree with that statement about waterborne coatings being much improved over the ones available even 5 years ago. The technology has really advanced.

http://www.woodworkingnetwork.com/cabinets/waterborne-or-solvent-based-experts-cant-tell-difference?utm_source=Real_Magnet&utm_medium=Email&utm_term=byhammerandhand@yahoo.com&utm_content=DAILY BRIEF&utm_campaign=Waterborne or solvent-based%3F Experts can't tell the difference