As is true of most "water-white" topcoats, General Finishes water-based topcoats dry clear over non-reactive substrates, such as plastic or metal, except General Finishes Enduro-Var, which ambers. When white paint sealed with a water-white topcoat is applied to something as unpredictable as wood, all bets are off and the reason for yellowing is often unknown. It can be caused by topcoat activating tannins in raw wood or aniline dyes, stains, or contaminants in a pre-existing finish. This is most evident when using BRIGHT WHITE paint and most prevalent in sculpted details of furniture where the topcoat can collect, intensifying color change to an unacceptable level.

There is no reliable way to predict whether yellowing will occur and to what degree. Every existing finish is different and we rarely know the finishing provenance on an existing piece. Every tree is different and every piece of wood is unique. Raw wood can bleed tannins immediately after the topcoat dries or months later with seasonal temperature changes. Oak, pine, mahogany, and douglas fir are particularly prone to bleed-through.

Summary

• Whites have a lower “hide” quality and are more transparent than most other colors. Nearly all bright whites require additional coats to achieve the desired color and minimize color variation. This can increase the cost of paint finishing. Always include a clause in your contracts addressing the need for additional coats to achieve coverage.
• All bright white paint will yellow slightly with time, with or without topcoat. You have probably tried to touch up white woodwork in your home after several years and noticed the new paint is brighter.
• The underlying finish or wood species can affect the final color of light paint.
• Details and inside corners are difficult to cover with any paint color, but it tends to be more noticeable with whites. This is a naturally occurring phenomenon in paint application and does not necessarily constitute a defect in the paint finish or your technique.
• The more porous the paint, such as a chalk paint, the more likely that yellowing will occur. The topcoat is seeping through the spaces caused by the larger particles of filler that give Chalk Paints their texture.

Tips to Prevent Yellowing

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• If it is a low-use project, use a premium white paint that is self-sealing and does not require a topcoat. A clear topcoat is not required on General Finishes Milk Paint for increased durability, as it is a self-sealing, exterior-rated coating with high durability and chemical and water resistance. However, topcoats do provide a smooth surface that is easier to clean and boosts durability for high-use projects, such as tabletops and kitchen cabinets.
• Use a professional spray such as General Finishes Enduro White Poly. It has "increased topcoat properties," is a standalone finish when 3 coats are applied, and does not require sealing with a topcoat.
• We recommend using General Finishes Stain Blocker, an engineered chemical barrier, to prevent persistent bleed-through for interior-use projects.
  • Stain Blocker does not adhere to melamine cabinet veneers.
  • Stain Blocker cannot be tinted.
• Always test your project's ENTIRE finishing schedule (from cleaning to topcoat) on an inside door or a more hidden area of the piece. This will not help if the yellowing occurs later, but at least you will know if there is an immediate problem.
• Avoid painting period furniture, such as a 1940s serpentine mahogany desk, with light colors. The pieces were often finished in stain that contained aniline dyes, which cast a pinkish bleed-through under light paint. Not every piece of furniture is suitable for upcycling with a light paint color. Pine, mahogany, and furniture of the 1940s and 50s are a red flag.
• Last, not all manufacturers' topcoats are compatible with other finishes and may react with a color change. Always follow best practices by not rushing, and testing to your satisfaction first.

Knots
Knots in wood tend to bleed and are dense, making paint and stain adhesion a challenge. Stain Blocker may improve adhesion and prevent bleed-through for painting projects. Pine knots are especially difficult to cover with white or light paints. If you decide to paint over them, apply 3 coats of Stain Blocker first; however, we cannot guarantee adhesion or bleed-through blockage. You are better off using a dark paint on pine.

Cleanup of Water Based Products