More on nail polish

Base coat, top coats and polish

Different formulations of the basic components are used for these three types of nail polish. Base coats typically are pigment free and thus can be optimised for adhesion to the nail and the subsequent layers as well as providing good coverage with the minimum of effort. Three strokes should be enough if the brush has been properly loaded. One down the centre starting from the cuticle followed by one either side. For good adhesion one would expect more of the tosylamide-formaldehyde resin. However, it is hard to find the precise percentage compositions. One rough guide is that OPI advertise their Natural Nail Base Coat as having more of this resin than nitrocellulose. Notice in this case the base coat is not pigment free, Red 33 is used to give a “natural” colour to the nail. Nail polish naturally contains the pigment while the top coat is a clear coloured formula aimed at providing a hardened barrier to prevent damage to the coloured layer. Here again we can look at the ingredients to get some idea of the relative amounts. Unlike the base coat the main film former is an acrylate copolymer and smaller amounts of cellulose acetate. A quick drying top coat is simply one with more solvent and because the solvent evaporates so quickly a different film former is needed, hence the acrylate copolymer. Also because there is more solvent these will tend to be runnier formulations. With all these unusual chemicals being put on the nail and close to the skin it is hardly surprising they must all be approved by the various regulatory bodies. One last thing, how do you get a matte finish? By creating a roughened surface for the film and one DIY way of doing this is adding cornflour! http://www.labmuffin.com/2013/07/how-does-matte-top-coat-work-and-diy-matte-top-coat-recipe/
Commercial matte nail polishes such as Barry M matte Nail Paint contain small particles of silica, typically 40 um silica gel, too big a particle and the surface will be gritty.