Varnish is a solution of solids in liquids that can evaporate and dry up. The solids may be either resins or artificial polymeric compounds, and the solvents may be ethyl and methyl alcohols, essential and vegetable drying oils. When applied the resin solution dries leaving a thin, crystal and shiny scum. At first the varnishes were used to protect surfaces but now the decorative qualities of various varnishes are very much appreciated.
In the modern handmade the acrylic varnishes are most often used as they are quite cheap and available. For work including contact with food or intended for children it is better to use water-based varnishes - they are more environmentally friendly and harmless.
Finishing and protective varnishes are glossy and matte or satin. They can be used in art, decoupage, creation of jewelry and dolls. The satin varnishes create a matte flexible scum, glossy give brilliance to the finished product. The high-quality varnishes do not get yellow with time and are good in contact with water and soft detergents. You should remember that before applying the varnish on the paint, you must wait till all the layers are absolutely dried. Some aerosol varnishes are recommended to be applied on products not earlier than 6-8 months after the product is finished. One of the new types of varnish is vitreous, when applied it creates a scum similar to glass resistant to scratches. Such varnishes may also include a glitter that gives the products the light twinkling or crystals.
One of the most popular types of decorative varnish is craquele. It gives the product an aged, cracked look. Cracks in such varnishes can diverge either arbitrarily or in the form of a thin spider web. Craquele varnishes are one- and two-component. The latter are in fact two varnishes - first, the first step is applied, waiting until it dries to a state of half-adhesion, the master applies the second step that creates cracks interacting with the first one. Single-component varnishes are applied directly on the surface. When working with such varnishes remember that the thicker the layer of the varnish, the wider and more textured the cracks will be.
Facet varnish - similar to the craquele one, when applied creates an image similar to the cracked glass. It is applied with a spatula and is evenly distributed over the surface. The thicker the layer, the thicker the lines. This varnish exists in various colors - gold, silver, copper, turquoise, etc.
3D effect Varnish is used to give volume, highlight some details, for example in decoupage.
Transfering varnishes (transcrils) can be also glossy and matte. They are used to transfer the images from photos, newspaper and magazine clippings, etc. to other surfaces. Such varnishes are applied in 4-5 layers perpendicular to each other that should be completely dried. Then the desired fragment is put into the warm water for 20 minutes and separate it from paper. The image you get is transferred to a flat hard surface, glued and covered with the varnish.
It is hard to give clear universal instructions for working with varnishes with such a huge variety of manufacturers and brands, but when working with any of them remember that this is a rather toxic material and safety should always come first.