What is an ideal condition for applying a nail hardener?

Applying a nail hardener is most effective after removing all nail polish. This is important because the presence of nail polish can interfere with the hardener's ability to adhere properly to the nail surface. When nails are clean and free from any coatings, the hardener can penetrate the nail bed and provide the intended strengthening effect.

Other options present conditions that may not be suitable for the application of a nail hardener. For instance, applying the hardener when nails are wet can prevent it from bonding effectively, while doing so during a foot bath might dilute the product's efficacy. Applying it before any other nail treatment can also be problematic, as it may compete with other products for adhesion or could be compromised by subsequent treatments. Therefore, the best practice is to ensure nails are bare and clean for optimal results with a nail hardener.