Which is better oil-based or water-based urethane floor varnish?

Answer 1

New Answer

The sine qua non (without equals) of clear finishes is two part automotive urethane clear coat. Its more flexible, more scratch and scuff resistant, more UV resistant, more washable, and more waterproof than any of the single part water borne or oil modified polyurethane coatings. The automotive finish catalyzes the polymer and cross links it in place. Water and oil carried finishes use pre cured and linked polyurethane that has been finely ground like a pigment and bind it in place with a latex, acrylic, or alklyd enamel. The final finish from a one part water or oil base coating is partly polyurethane (15% to 60%), generally the higher the percentage, the more durable the coating.

2 part catalyzed urethane clear coat can be reduced, sprayed, brushed, rolled, etc. It cures faster than even water based varnish and its easy to apply multiple coats in an afternoon, but if the (1-2 hours) recoating interval is missed it can't be recoated until fully cured and sanded. The very brief tacky interval minimized dust and lint inclusions in the finish, and unlike varnish they can be spot sanded and polished

Automotive style urethane clear coat can be wet sanded and polished to any degree desired, but its difficult to achieve a satisfying semi-gloss or satin finish.

Wet automotive style 2 part catalyzed urethane clear coat is unfortunately extremely odiferous. This is partly because the rapid drying and curing causes almost all the smells to evolve in the first hour. Not merely unpleasant, its unhealthy to breathe it routinely without protective gear. For reference, acetone, often used for tool and hand cleaning with urethane, is somewhat less odiferous.

2 part automotive urethane clear coat is also more expensive than any of the one part coatings. Expect to pay more like $75 to $150 per gallon for the coating, and catalyst, $30/gallon for the reducer (thinner). The higher cost per gallon is partly offset by the greater build factor, that is to say, you get more thickness per gallon, but the final material cost per square foot of floor is still at least 50% higher.

The high material cost and pungent fumes make this best choice coating material rarely used, even by those who have the equipment and experience.

So having explained what the BEST choice is, its easier to understand that the following answer about the best practical choice is indeed in large part the tradeoff between coating quality and smell. Water based varnishes have the least odor but the tag line "much better in the last 3 years" has been repeated for many years. The essential problem is that water borne acrylic binder doesn't bond to urethane so the need to encapsulate limits the urethane content, resulting in a less durable surface.

Prior Answer

Curious about the differences between oil based and water based hardwood floor finishes? I consulted with an expert on the subject, Elektra Grant, an associate with Livingreen. The following, based on Elektra's expertise, is a tell-all product comparison reviewing the many differences, similarities, benefits and drawbacks the consumer should be aware of before making a final product purchasing decision.

Water Based Finishes

If you choose to lay down a water based finish, you have the benefit of a second, aesthetic choice. Water based finishes are separated into two categories: gloss & satin. The gloss finish will leave your wood floors with a clear, reflective shine, where the satin finish will give your floors more of a 'matted' look. When choosing between gloss and satin, it is very important to note that the satin finishing process is a rigorous process which will in all likelihood be more costly. The reason: when applying satin finish coats (you will be applying no less than two) it's necessary to lay down a final gloss finish coat over the last coat of satin. A satin-on-satin finish will leave your floors looking hazy or cloudy.

One of the biggest differences between water based finishes and oil based finishes is the discrepancy in drying time. Water based finish products dry more quickly on a hard wood surface, taking only a fraction of the time it takes an oil based finish to dry or cure. (Under normal conditions, a water based finish will dry to the touch in one hour and can be re-coated in two.) Elektra recommends that if the water based finish is to be applied by hired professionals, that the workers work as a team to lay down the finish coat in 'one shot'. The reason: lap marks. Lap marks occur when a wet finish coat is applied over an already cured finish coat. The result is a permanent discrepancy in color. Because of lap marks, although a water based finish can be applied somewhat easily with a bristle brush, paint roller or spray, the water based finish can be more difficult to apply quickly and correctly by a novice. It's often recommended that the finishing be done by professionals. With the water based finish, it's recommended that you sand in between the application of each coat. You don't want to sand away the entire coat, you simply want to sand the surface so that each coat will 'grip' the coat laid previous.

In terms of a water based finish product, Elektra recommended AFM Safecoat®, a product carried by Livingreen which can be purchased online or in store at any Livingreen location. The product is offered in a consumer standard, single quart or gallon drum for $88.90. The one gallon drum will cover roughly 300 to 350 square feet of floor space. It is advised by the manufacturer that a minimum of two coats be laid down, though three or more (likely no more than four) is recommended. AFM Safecoat® offers both the gloss as well as the satin finish. AFM Safecoat® has been in the business of engineering and reengineering conventional finish sealers for over twenty-five years and for over twenty-five years they have considered human healthy to be a top priority. Water based finishes have advanced greatly in that time; they are now considered by many professionals to be equal to, if not superior to any oil based alternative.

In general, it's recommended with water based finishes that you purchase a separate polyurethane finish to apply as a final coat on top of the two or more already applied water based finish coats. However because AFM Safecoat® is already a solution which comprises a sufficient ratio of polyurethane, the separate and final coat is not necessary, which makes AFM Safecoat® a good product choice. However, considering the need for multiple coats, water based finishes are still likely to cost more, on average. Unlike the oil based finish solution comprised of natural oils, AFM Safecoat®is a synthetic solution. Yet, surprisingly it's lower in VOCs (volatile organic compounds) than the oil based alternative, making it more eco-friendly. Since its founding, It has been AFM Safecoat's objective to minimize if not eliminate entirely all ingredients that are harmful to human health.

Contrary to the widely held belief that water based finishes are odorless, Elektra who has a great deal of experience with both finishes claims that neither is perfectly odor-free; they both have their own distinct odors - the oil based finishes, for example, smell of natural oils (the product includes soybean, sunflower, linseed, and other natural oils.) Elektra does not claim that either is necessarily noxious - unless of course the individual experiencing the odor has a specific aversion to that odor.

Another major difference between a water based finish and an oil based finish is the difference in durability. Elektra considers water based finishes to, in theory, be a more durable product because it acts like a hard protective shell of plastic coating, sitting on top of the surface of the wood like paint.

Because it goes down like paint, the applicant tends to have a greater reflection and shine; oil based finishes have a more natural apearance in comparison. To avoid choosing the wrong applicant, the best that can be advised is to test the finish out on a sample piece first. If you are truly unsure whether or not to use an oil based finish or a water based finish, testing both samples in the store or asking to see previously tested samples might be a helpful in determining what product will look the best in your home.

Oil Based Finishes

An oil based finish is sometimes preferred to a water based finish because the oil based finish is said to give the wood more depth and more color. The oil based finish is absorbed into the wood and the oils penetrating the wood surface will accentuate the wood grains, giving them more presence. The natural oils in the sealer which penetrate the surface of the wood give the wood a muted but natural-looking and long-lasting shine. Additionally, when the wood absorbs the oil based finish, the wood absorbs moisture which helps to keep the wood from drying out and cracking over time. With the oil based finish, you only need to apply two coats. You want

to apply only a thin initial coat, followed by a heavier second coat. Though you don't need to sand in between coats, it's recommended that you finish by buffing the surface of the second coat. Oil based finishes require nearly 24 hours to dry in between coats and can take up to two weeks to fully cure. In that time, it's likely you will experience an odor of natural oil. The odor however, will dissipate. Note: It is very important during the application process and throughout the drying period to have proper ventilation, so keep windows and door open whenever possible.

In terms of oil based hardwood finish products, Elektra recommended OSMO Polyx®-Oil. It's a little more expensive in comparison (costing $105.99 per 2.5 liters, a little less than a gallon) though again only two coats are required. (Safecoat® also manufactures a comparable oil based finish, if you choose to be brand loyal.) A major benefit to the OSMO Polyx®-Oil product: The wood floor can later be spot repaired if need be. OSMO Polyx®-Oil will allow you to touch up the floor without leaving a trace (a lap mark,) where with a water based finish you would have to sand down the whole floor and refinish it to give it the same new look.

'Yellowing' is a common concern with oil based finishes; the wood is said to take on a yellowed tinge after time. However Elektra, whose apartment floors were finished with an oil based product, claims the floor shows no sign what-so-ever of 'yellowing.'

In truth, oil based finishes in comparison with water based finishes are higher in VOCs, however the difference is slight. All floor finishing products have a VOC presence, but both OSMO Polyx®-Oil and AFM Safecoat® are extremely low by comparison in VOCs. Important Note: Rags contaminated with and oil based finishing product are a combustible hazard and should be sealed in a water filled, watertight metal container and disposed of properly by way of your local Household Hazardous Waste Facility.

In review, I find the ultimate difference between oil based and water based hardwood floor finishes, when boiled down, is aesthetic. All things considered, this is what I recommend: Compare test samples of each finish variation in the store to see first-hand the visceral differences before you make a final purchase. Then do the math, estimate the ultimate cost of time and money after considering the following factors:

• The cost of each drum of product required to cover your floor space, added up
• The cost of DIY versus hiring professionals
• The cost of sanding versus buffing
• And, the time each product requires for application and curing