Many nail files are made with sand "papers" that bond the grit to the paper with glue. Different adhesives are used to bond the abrasive to the paper. Hide glue is still used, but this glue is not waterproof. Any nail file manufactured with this type of glue would not be considered waterproof and described as "non-washable".
Waterproof or "washable" nail files use a resin bond adhesive and a waterproof paper backing. This permits the nail files to be cleaned and used again by washing in water or other disinfectants and will not swell, shred or peel apart.
Some sandpaper used on nail files may also be "sterated" where a dry lubricant is loaded to the abrasive. These types of files are commonly known as "Zebra" files in the nail industry.
Zebra abrasive paper is made with black silicone grit and then coated with white zinc sterate powder. This paper comes in a washable and non-washable version. The non-washable version is not made from hide glue however. It's powder substrate material is not bonded in a way that is waterproof as is its cohort the washable type.
In addition to paper, other common backing for sandpaper used to make nail files includes cloth (cotton, polyester, rayon). Cloth backing is commonly used on 3-Way high shine buffers and blocks. Any porous and/or absorbent items constructed of materials such as cloth, wood or open-celled foam with surfaces that may absorb or are penetrated by liquids and cannot be disinfected properly should be deemed as a one time use item in the salon environment.
An even stronger backing than either paper or cloth used to make sandpaper is mylar or polyester which is a very thin plastic. Mylar backing is commonly used on Sterifiles and lasts 2 - 3 time longer than paper backing nail files. Because mylar nail files are non-absorbent they can be immersed for more than 1 hour.
Another washable type of abrasive that can be immersed for hours is made from closed-cell foam and the abrasive is bonded directly to the foam with no paper or mylar substrate in between. It is usually thicker foam than found on the typical cushioned abrasive files which provides an easy comfortable grip for the nail technician and because there's no paper, there's no paper cuts to the clients. This type of abrasive sponge is commonly used on Sponge Boards.
A "Standard" nail file made with washable sandpaper can be immersed for up to 5 minutes in a warm or hot water, antibacterial soap, isopropyl or ethyl alcohol solutions. The "Premium" grade nail files can be immersed as the "Standard" but may also be immersed in EPA-Registered disinfectant for up to 10 minutes. While the mylar Sterifiles and closed cell Sponge Boards and Blocks can be immersed in either for more than 1 hour.
Click here for Proper Disinfection of Cushioned Abrasive Files, Buffers and Blocks instructions.