When is a nail strengthener applied during the manicure process?

A nail strengthener is applied before the base coat during the manicure process. This step is crucial because nail strengtheners help to fortify and protect the natural nail before any additional products are applied. By applying the strengthener first, it can penetrate the nail, providing treatment and enhancing its resilience.

The base coat is designed to create a smooth surface for the polish and help it adhere better, while the strengthener's primary function is to improve the condition of the nails. Applying the strengthener prior to the base coat ensures that the benefits of the strengthener are maximized and can effectively contribute to healthier nails, making it an essential part of the manicure.

In this context, the other options suggest applying the strengthener at a time when it would not provide its intended benefits, such as after filing or before polish application, which are not optimal for encouraging nail health and strength. Thus, placing the strengthener at the beginning of the process capitalizes on its protective qualities.