People use “varnish” and “polyurethane” interchangeably, but they’re different products with different strengths. Here’s the practical breakdown.
Traditional Varnish
Made from oils and resins – linseed or tung oil combined with hard resins. Takes days to cure fully. Penetrates the wood and builds a finish from within.
Marine (spar) varnish stays flexible and handles UV exposure. That’s why it’s still preferred for boat brightwork and outdoor furniture. Nothing beats it for sun and weather resistance.
Polyurethane
A modern synthetic that forms a hard plastic film on the wood surface. Extremely durable against scratches and water. Dries faster than varnish. Available in oil-based (warmer, slower) and water-based (clearer, faster).
The film sits more on top of the wood rather than penetrating. This makes it tougher but can look more plastic-like on some woods.
Which to Choose
Kitchen tables and floors: Polyurethane. You need the durability and water resistance.
Outdoor furniture: Spar varnish. It handles UV and weather movement better.
Fine furniture: Personal preference. Varnish looks more traditional. Poly is more practical.
Antique restoration: Match the original finish.
Application Notes
Both need thin coats and sanding between. Polyurethane is touchier about dust and brush marks – work in a clean space. Varnish forgives more but takes longer.
Wipe-on versions exist for both and are much easier for beginners. Thinner coats, more coats, better results.
The Real Answer
Either finish will protect your work. Pick based on your specific needs and learn to apply it well. Technique matters more than the product.
