Where should plastic filler be mixed?

• A. Non-porous
• B. Porous
• C. Rough
• D. Wet

Answer: (A)

Plastic filler should be mixed on a non-porous surface. When the filler’s resin and hardener sit on a non-porous surface, they stay exactly where you mix them and cure predictably, giving you a smooth, workable blend. Porous surfaces would soak up some of the liquid components, altering the mix ratio, changing cure time, and possibly introducing moisture or contaminants that weaken the repair. A clean, dry, non-porous surface—like glass, metal, or a dedicated mixing board—helps you achieve a consistent mix and a proper, uniform fill. Mixing on a wet or rough surface can also lead to contamination or an uneven finish, which is why non-porous is the best choice.