When it comes to wood finishes, it seems like the options are infinite in terms of what types of wood finishing systems may be the best fit for your particular project in both allowing maximum beauty & durability in balance with whatever conditions may be at play.
Two prominent finishes that, when applied properly and cured appropriately, offer long-lasting protective coatings are polyurethane and varnish.
Many times, people refer to polyurethane as ‘varnish’ and varnish as ‘polyurethane’.
Polyurethane and varnish are actually two definitively different products with each having performance elements which differ from the other.
Polyurethane is kind of like a liquified plastic.
Polyurethane comes in either acrylic or oil-based forms.
Although resembling “milk”, polyurethane applies as a clear finish.
Whether acrylic or oil-based, polyurethane is very popular for many interior uses with everything from furniture to floors.
The acrylic-based polyurethane will tend to keep its clear appearance over time where the oil-based polyurethanes will gradually “yellow” out on you.
The term ‘varnish’ is often used by people unknowingly utilizing it to describe a myriad of wood finish examples (including polyurethane).
Actual varnish however is an oil-based finish which, similar to oil-based polyurethanes, will cure to a faint yellow film or possibly even an amberish tint.
Due to the high-solid content of the finish and how well it holds up against moisture, varnishes are often favorite finishes for outdoor furniture, decks, and boats.
A variant of varnish – referred to as spar or marine varnish – is particularly good in guarding against Ultraviolet (UV) rays.
Both polyurethane and varnishes can be tricky to apply and if they are not used in-line with the manufacturer’s recommendations, can result in finishes that are less than ideal (with the appearance of bubbling, cracking, wrinkling becoming visible as the finish dries).
If each is applied properly, polyurethane and varnish can look absolutely stunning.
This all being said, which would I recommend for what?
I usually go by the rule of thumb where we utilize polyurethanes as part of our interior wood finishing systems and varnishes for our exterior wood finishing systems.
The idea (in my head at least) is that polyurethanes are terrific for hardwood floors and the like, specifically because of their durability and flexibility in comparison to varnishes.
Varnishes, because of how much better they stand up to UV rays, are what we usually aim to incorporate into our exterior wood finishing systems.
Now, if you were to ask this same question to a variety of self-proclaimed wood finishing “snobs”, there may certainly be nuanced debate as to what is best to use where.
This is simply the guidance from my end with the intention of keeping things simple.
One thing is for certain though, the gorgeous nature of what polyurethane and varnish systems embody in their role of both enhancing and protecting a wide variety of wood species that we use throughout everyday life, cannot be denied and is super impressive when seen ‘before’ and ‘after’ by someone who truly embraces the art of applying either one.
