What is the function of a scratch comb?

What is the function of a scratch comb?

• A. To measure thickness
• B. To create a uniform scratch pattern on the scratch coat for bonding
• C. To apply the final coat
• D. To level the surface

Answer: (B)

Keying the surface for the next coat is essential in plastering. After applying the scratch coat, you run the scratch comb across the still-plastic plaster to create shallow grooves in a uniform, cross-hatched pattern. Those grooves form a mechanical key, increasing the surface area and giving the next coat something to grip onto. That improves adhesion and helps prevent delamination between coats. This tool is not for measuring thickness, applying the final coat, or leveling the surface; those tasks use other tools and steps.

Keying the surface for the next coat is essential in plastering. After applying the scratch coat, you run the scratch comb across the still-plastic plaster to create shallow grooves in a uniform, cross-hatched pattern. Those grooves form a mechanical key, increasing the surface area and giving the next coat something to grip onto. That improves adhesion and helps prevent delamination between coats. This tool is not for measuring thickness, applying the final coat, or leveling the surface; those tasks use other tools and steps.