What's The Difference Between Traditional Varnish & Polyurethane?
Everyone appreciates the elegant look of wood floors, cabinets and doors, but the ravages of time can leave fine wood looking old and neglected. In order to better preserve the inherent beauty of wood furniture and fixtures, a traditional varnish or polyurethane top-coat finish is usually applied. The downside is that this protection comes with a hefty cost in terms of harmful chemicals, strong odors and environmental damage.
While varnish and polyurethane are often used as synonymous terms, they are very different products and not interchangeable.
What is Traditional Varnish?
Traditional varnish has evolved to include a number of derivatives, but the basic product includes a combination of solvents, resin, drying oils and UV protectors. Furniture makers and wood workers have traditionally used conventional varnishes to give wood a durable and flexible finish as well as protect it against damage from the sun.
There are three primary elements in varnish that give it the appealing properties that consumers and woodworking professionals desire. Unfortunately, these components also create noxious odors and present serious health risks.
Resin: Resin is a viscous material in varnish that is typically made from dammar, copal, balsam, sandarac and other organic materials.
Drying Oil: When exposed to air, drying oil forms a hard film surface. There are several different drying agents including tung and walnut oil.
Solvents: A solvent allows the base material to cure as it evaporates. Turpentine is still used extensively in varnish products, but mineral based substitutes have grown increasingly popular.
Applying a conventional varnish finish isn’t particularly easy, and those with experience usually get the best results. If done improperly, conventional varnish can bubble, peel, crack, delaminate or never fully harden.
It is also important to apply conventional varnish in an environment free of dust, dirt and other contaminants. In most cases, several coats are required to produce the desired effect.
What is Polyurethane?
Polyurethane is a sealant and finish product that is used to protect and enhance fine wood floors, cabinets and furniture. While it is similar to varnish in terms of application and appearance, polyurethane is generally harder and more abuse resistant, which means it is commonly used for sealing wood floors.
Unfortunately, polyurethane is less flexible than varnish, so it may not be the best choice to use on wood pieces that move or flex.
Water-based polyurethane finishes are comprised of a resin suspended in water and solvent. As the water evaporates from the resin, the material transforms from a liquid into a film.
Oil-based polyurethane cures in a slightly different way. The solvents evaporate from the material, which allows the oils and resin to harden
Traditional Varnish and Polyurethane Toxicity Issues
Water-based polyurethane can have less of an offensive odor when compared to oil-based products, but floors require at least four coats to achieve the desired level of protection. While oil-based polyurethane only needs two or three coats, the odor may be so strong the home is uninhabitable for several days.
At its core, polyurethane is a petrochemical resin that contains isocyanates. Uncured polyurethane can aggravate a variety of different breathing problems including allergies, asthma and bronchial conditions.
Additionally, those who are exposed to the fumes may develop vision difficulties, throat irritation, nausea, uncontrolled coughing, vomiting and headaches. Isocyanates contain compounds that are classified by the EPA as potential human carcinogens.
The resins and solvents used in varnish are toxic if ingested. Many varnish products contain benzene, which is a known carcinogen that is highly flammable. The solvents in varnish are extremely pungent, and the fumes can cause drowsiness, headaches, skin irritation and dizziness.
At high concentrations, a person may become unconscious, suffer respiratory distress and may even develop pulmonary edema. Those who apply varnish should always wear a mask, and those with respiratory conditions such as asthma may want to avoid contact with varnish completely.
The ECOS Solution:To address the toxicity issues associated with traditional varnishes and polyurethanes, ECOS developed their WoodShield varnish product that is non-toxic* for human health and has no offensive odors.
ECOS WoodShield is designed for use on furniture, cabinets, floors, woodwork and doors and is available in a wide array of sheens. The water-based varnish has exceptional clarity and durability, and it can be applied with the same applicator tools commonly used with polyurethane.
ECOS – Performance without compromise.*Conforms to ASTMD-4236, specifically concerning oral toxicity, skin irritation and respiratory effects.