Adhesive

• Some part of the finish used to coat bathtubs is adhesive in nature, allowing the finish to attach to the old surface and bond with it properly. Whether or not the old surface has to be completely sanded down first depends largely on the tub, but then some type of chemical adhesive is usually necessary. For stone bathtubs or those made from porcelain, a sealant may be used instead and a direct adhesive may not be necessary.
  
  

Urethanes

• An acrylic urethane mixture is one of the most common types of finish used on bathtubs. This provides the shine, protection and feeling associated with the common bathtub. It is also highly toxic in spray form, which is one reason that bathtub refinishing must be conducted by professionals in an enclosed environment, with the aid of respirators.
  
  

Epoxies

• Epoxies are a group of plastic resins designed to fill or coat surfaces and then dry, making them a common ingredient in many types of bathtub recoatings. Epoxies are useful both for small repairs and sealing leaks or cracks in the bathtub. They may be used to prepare surfaces for a more traditional coating when flaws need to be filled in, or may be an integral ingredient in the primary coating itself.
  
  

Chemical Protectants and Hardeners

• There are also many different types of extra chemicals in the coating materials that perform specific jobs. Protectants help reinforce the coating and prevent damage from scrapes and scratches. Hardeners are often necessary when using epoxies, and create a chemical reaction when exposed to air and the epoxy resin that sets the mixture.