Which tool size is recommended for applying the second coat of joint compound on new gypsum panels?

• A. Apply with a 300 mm (12 in.) knife, feathering beyond.
• B. Apply with a 200 mm (8 in.) knife, feathering slightly beyond the first coat.
• C. Apply with a 100 mm (4 in.) knife, feathering.
• D. Trowel-only application.

Answer: (B)

When finishing joints, the second coat should smooth and blend the seam into the surrounding wall, using enough width to feather out beyond the first coat. An 8-inch (200 mm) knife is ideal because it provides enough reach to cover the seam and extend past the edge of the first coat, creating a seamless transition with a thin, even layer. Using a larger knife, like 12 inches, can overload the mud and make feathering harder to control, while a smaller knife, like 4 inches, won’t blend as effectively. Trowel-only application skips the controlled feathering a knife offers, so it isn’t suitable for this step.