What Varnish Can Be Used Over Latex Paint?
- Latex (water-based) paint dries quickly but cures slowly. This is an important distinction to understand when considering a coat or two of varnish over latex paint. It feels dry to the touch within an hour because the surface of the paint film quickly forms a dry skin. However, the underlying layer of paint is still wet. To be fully cured, all moisture has to evaporate through the paint.
- There are two main types of varnish: Oil-based and water-based. Subtypes include synthetic blends like polycrylic, acrylic, polyurethanes, spar and linseed oil varnishes and oil-modified polyurethanes.
Water-based varnishes go on much like water-based paints. They dry quickly, have low odor, and tools can be cleaned in soap and water. Most water-based varnishes are non-yellowing and remain clear for years. Many will appear milky-white while wet and during application, but they dry to a crystal-clear finish.
Oil-based varnishes dry more slowly, have a stronger odor and require mineral spirits for cleanup. They are more viscous than water-based varnishes and usually require fewer coats to achieve a smooth, even gloss. Most will yellow over time, which gives old varnished wood an aged, soft patina and color. - Almost any type of varnish can be used over latex paint. However, oil-based varnish should be used only over paint that has cured for a minimum of 60 days. If the paint is not fully cured, slowly evaporating moisture will be trapped under the varnish, causing it to become cloudy and dull. Water-based varnish can be used over latex paint after eight hours of drying time. Both types of varnish may slightly yellow the paint color, although oil-based varnish is more likely to do so.
- Acrylic or polycrylic varnish is sometimes recommended over some faux finishes. However, the varnish is no more durable than quality latex paint. Rather than add the additional step of varnishing, use a high quality latex paint to begin with, and for heavy use or bookshelves, consider oil-based paint. Don't count on varnishing over poorly prepared surfaces and cheap paint for a long-term fix. When the paint and varnish start chipping and peeling, it's just one more layer to strip and sand.
- Some varnishes have added stain to make staining and varnishing wood a quicker project by combining steps. Using these, or any clear varnish with colorant added, can be used as a top coat over latex paint for giving an antique or aged effect. The end result depends on the applicators and techniques used.