It is a colorless, fuming, corrosive liquid with a boiling point of 19 degrees Centigrade.
Hydrofluoric acid reacts well with silicates and is used in etching glass.
It also has the ability to render rust virtually invisible when the rust is in fabrics. Since this acid is very low on the pH scale, great care must be used when working with it, and it must always be neutralized after being used, especially with fabrics.