Varnishes are known for their durability and toughness. They can come in various "sheens" (shininess). They can be oil-based or water based and are made of synthetic resins.
Water-based Polyurethane
Essentially a plastic in the form of a liquid until it dries, uses water as a thinning agent.
- Toxicity: low odor and low toxicity.
- Look: It goes on clear without adding a slight color that oil-based versions can. Comes in Satin, Semi-Gloss and Gloss. Has a "Plastic" look and feel to it, more the thicker it's applied.
- Cons: It doesn't hold up well to heat
- Pros: Provides a tough, protective coating, with outstanding hardness.
Oil-based Polyurethane
Essentially a plastic in the form of a liquid until it dries, uses oil as a thinning agent.
- Toxicity: High odor and High toxicity.
- Look: It adds a slight color tone and will bring out the richness of wood. Comes in Satin, Semi-Gloss and Gloss.
- Cons: More durable then water-based to heat and chemicals. Takes a long time to dry (fast drying versions are available, but they are hard to work with).
- Pros: High abrasion resistance, Easy to apply.
Varnish
The name of this finish often is used generically for a finish or top coat. It's very durable because it contains a higher ratio of solids. Spar varnish is perfect for outdoor projects and for raw wood used for exterior doors and trim on rustic homes.
- Toxicity: Toxicity: High odor and High toxicity.
- Look: Clear natural look
- Cons: It can dull or yellow over time, Long drying time.
- Pros: Provides natural ultraviolet light protection, high resistance to water and heat. Easier to apply by brush then Shellac.
- Uses: Varnish is often used on items that will be near or on the water and for outdoor projects.