Oil Painting Varnishes And Mediums

Varnish serves multiple functions in a painting medium. Firstly, it improves tack, which refers to the ability of the paint to adhere to the surface. Secondly, it imparts an even gloss, giving the painting a uniform and attractive finish. Lastly, varnish helps retain the wet appearance of colors, preventing them from drying out and losing their vibrancy. Therefore, all of the given options are correct functions of varnish in a painting medium.

Expeller pressing releases compounds undesirable in oil used as a painting vehicle and medium. Alkali refinement removes these compounds, resulting in a stable, clear oil with good film-forming properties.

Oil-saturated rags, rubber gloves and steel wool can act as insulators while spreading oil over a large surface area. As oil quickly oxidizes, heat can build and materials can ignite. Single rags can be laid flat to dry, or placed in a metal lidded trash can with water for nightly disposal.

Retouch Varnish offers uniform gloss and protection from dust for paintings that are not yet dry enough for a final picture varnish.

A picture varnish should be removable with light-duty solvents to facilitate cleaning and conservation.

Alkyds are made from soybean or other oils.

Matte varnish can generally be applied on top of gloss varnish of similar composition without removing the original coating. For the reverse order (gloss over matte), the matte layer should first be removed.

Genuine shellac is derived from insects.

Painting into a "couch" involves painting in a uniform layer of wet paint or medium. This technique facilitates detail and suave transitions with subtle or nearly invisible brushstrokes.

Stand oil is linseed oil that has been heat-polymerized in an oxygen-starved environment. Heat-polymerization is a process in which the oil is heated to a high temperature, causing the molecules to cross-link and form a thicker and more stable substance. In an oxygen-starved environment, the oil polymerizes without the presence of oxygen, which prevents the formation of a skin or film on the surface. This makes stand oil ideal for use in oil painting as it dries slowly, has a high gloss, and enhances the flow and leveling properties of the paint.

Cobalt drier is a "top drier" that induces skinning. Excessive use in painting medium can cause wrinkling, darkening and embrittlement.

Copal must be "run" by heating and dissolved in very hot oil; it will not dissolve in turpentine or mineral spirits at room temperature.