What happens if too little hardener is used in filler application?

Using too little hardener in a filler application can significantly affect the adhesion properties of the filler. When the hardener is not adequate, the chemical reaction that is responsible for curing and setting the filler is compromised. This leads to insufficient bonding between the filler and the metal surface, resulting in poor adhesion. If the filler fails to adhere properly, it may eventually fall out or be unable to support any surface repair, making it crucial to adhere to the recommended ratios of filler and hardener for optimal performance.

While some of the other choices might address issues related to filler performance, they do not specifically capture the critical aspect of adhesion as directly affected by the quantity of hardener. This highlights the importance of following manufacturer guidelines during the mixing process to ensure effective outcomes in collision repair and refinishing.