A painting contractor is applying a clear, penetrating wood sealer to a new redwood deck. The manufacturer's instructions state to apply one coat and wipe off any excess after 15-20 minutes. The contractor applies a heavy flood coat and allows it to penetrate without wiping, believing more material will provide better protection. What is the MOST likely long-term consequence of this over-application?
- AThe wood will become darker than intended, but with no adverse performance effects.
- BThe sealer will cure harder and provide enhanced abrasion resistance.
- CThe penetration will be deeper, leading to extended waterproofing properties.
- DThe excess sealer will form a film on the surface that may peel or flake over time.
Show answer & explanationAnswer & explanation
Correct answer: D. The excess sealer will form a film on the surface that may peel or flake over time.
Penetrating sealers are designed to soak into the wood. Over-application, particularly without wiping off the excess, means that the material that cannot penetrate will dry on the surface. Unlike film-forming coatings, penetrating sealers are not designed to create a durable surface film, so this excess material will likely form a weak, non-adherent film that will crack, peel, or flake prematurely, leading to coating failure.
Why the other options are wrong
- A. While the wood might be darker, the primary issue with over-application of penetrating sealers is the formation of a surface film that will inevitably fail.
- B. Penetrating sealers are not film-forming and do not significantly increase abrasion resistance by curing harder on the surface; over-application typically leads to failure.
- C. Penetration depth is limited by the wood's porosity and the sealer's properties. Applying more than the wood can absorb will not significantly increase penetration depth but will leave excess on the surface.
Over-Application of Penetrating Sealers
Applying too much penetrating sealer, especially without wiping off excess, causes the material to form a weak, non-adherent film on the surface that is prone to premature peeling, flaking, or tackiness.
- Penetrating sealers are absorbed, not film-forming.
- Excess material on the surface creates a weak layer.
- Leads to premature coating failure: peeling, flaking, tackiness.
Memory trick: Don't let the deck wear a coat, or it will shed its skin and float.