What substance is commonly used to strengthen nails in a salon?

The substance commonly used to strengthen nails in a salon is nail hardeners. Nail hardeners are specially formulated products that contain ingredients designed to reinforce the structure of the nails, making them less prone to breakage and damage. They typically create a protective layer over the natural nail, enhancing its strength and durability, which is particularly beneficial for clients with weak or brittle nails.

Base coats also play an important role in nail care, as they prepare the nail surface for color application and can protect the nail from staining. However, their primary function is not necessarily to strengthen the nails but to enhance the longevity of nail polish.

Nail polish remover, while vital for the removal of nail products, does not contribute to strengthening nails. It can, in fact, have a drying effect on the nails if used excessively.

Moisturizers, although beneficial for the surrounding cuticles and skin, do not directly strengthen the nails themselves. Their main purpose is to hydrate and maintain the health of the skin around the nails.

In summary, nail hardeners are specifically formulated to strengthen the structure of the nails, making them the correct choice for this question.