What can happen if filler is applied too thick?

• A. It may crack or fail
• B. It will become stronger
• C. It will bond perfectly
• D. It will dry faster

Answer: (A)

Applying filler in a layer that's too thick invites cracking and failure because body filler cures from the surface inward and shrinks as it hardens. A thick build traps solvents and air and doesn’t cure evenly through the depth, creating internal stress. When the panel flexes or experiences temperature changes, that stressed, oversized patch is prone to cracking, pulling away from the metal or primer, and failing to hold up over time. Using thin, multiple coats allows each layer to cure evenly, bond well to the substrate, and be sanded smooth. Thick layers won’t make the repair stronger; they’re more likely to crack, and they don’t dry faster—in fact, they cure more slowly in the center.