Surface PreparationQuestion 18 of 100
Knots and sap streaks in bare softwood can bleed through paint unless they are sealed with what?
a.A thin coat of water
b.Only the finish paint
c.A stain-blocking primer (such as shellac-based or a dedicated knot sealer)
d.A coat of clear caulk
Explanation
Resin and tannins in knots and sap can bleed through ordinary paint, leaving yellow-brown stains. A stain-blocking primer, often shellac- or oil-based, seals the knot so it does not discolor the finish. Spot-priming the knots before the full prime coat is common practice.
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