Thinning your first coat of varnish or polyurethane creates a better foundation and helps subsequent coats adhere properly. This technique improves durability and appearance.
The Ratio
Mix approximately one part mineral spirits to three parts oil-based finish. For water-based products, use water in similar proportions. This thinner consistency penetrates the wood grain.
Why It Works
A thinned first coat soaks into the wood fibers rather than sitting on top. This creates mechanical adhesion. Full-strength coats applied over this foundation bond more effectively.
Application Method
Apply the thinned coat with a brush or rag. Wipe off any excess after a few minutes. Let it dry completely before applying full-strength coats on top.
Many professionals call this a sealer coat. It takes minimal extra time but noticeably improves finish longevity.
