Liquid sandpaper is a liquid substitute for conventional sandpaper in so far as it breaks down hard enamel finish making it more porous. This prepares the existing painted surface so that the new coats of paint can better adhere. This type of product is also known as liquid de-glosser and liquid etch.
It is always a good idea to clean the surface to be painted prior to applying a liquid de-glosser. Contaminants can interfere with the ability of the etching liquid to properly perform.
A liquid etching solution can be applied to a painted surface by wiping the material on with a clean, lint free cloth. Some brands require a minimal amount of rubbing while others only need to be applied and allowed to evaporate. You should only etch as much area as you can paint over within 30-45 minutes.
Liquid de-glossers have a clear advantage for certain applications.
Houses built before the mid 1970s have a high probability of having been painted with lead based paints. A liquid solution may be a good alternative to sanding, to avoid creating any lead dust particles in older homes.
Un-surfaced or re-sawn woodwork has a rough or uneven wood grain appearance where conventional sanding is not an option. Because an existing enamel finish still needs to be prepared, a liquid etching solution works well.
Liquid etch can be a big time saver for preparing trim with elaborate details. Conventional sanding can be very tedious when working through decorative designs.
Liquid de-glossers are only effective when etching existing paint coatings. They do not smooth over uneven surfaces. Conventional sanding is the only way to restore an existing rough, irregular painted surface into an even, professional looking surface.
Because of governmental air quality standards, liquid etching products may not be available in some regions. Its VOC content surpasses the allowable limits in some air quality districts.
Liquid etching solutions contain toxic chemicals. Avoid contact with eyes and skin. Wear chemical resistant gloves when using these products. Read the manufacturer’s directions for proper use and safety.
Because liquid sandpaper is a flammable liquid, use in a well ventilated area. Always dispose of flammable rags in a safe manner.