Venice Turpentine is a natural balsam or as sometimes is called, an oleo-resin. The only balsam we are concerned here is the Pure Larch Venice Turpentine, not the dark brown syrup we can see for sale in art shops. This dark brown syrup is a mix of Larch Venice Turpentine and other ingredients, usually not specified which represents a risk. Pure Larch Venice Turpentine is a pale yellow viscous transparent liquid. At room temperature, Venice Turpentine is almost impossible to handle, given its almost solid state. When lightly heated in a "bain-marie", it becomes liquid and easy to blend with either Turpentine, Oil (linseed or walnut) or both.
Pure Larch Venice Turpentine dissolves easily in Turpentine at a ratio of 1 part Venice T. to 1 part of Turpentine. Prior to mixing, heat Venice T. as indicated above, only enough to render it liquid.
If mixed with just oil, it is recommended to heat it as above and mix it at a ratio of 1 part of Venice T. to 2 parts of either Stand Oil or Sun-Thickened Oil. For details on both oils, please consult pages dedicated to Drying Oils.
A balanced painting medium would contain 3 equal parts of Oil, Turpentine and Venice Turpentine. Such medium is oil rich, so it will be advisable to thin it if you are planning to use it throughout the painting. Only the uppermost layers should contain a medium this rich in oils.
According to some authors, Van Dyck used it as an intermediate varnish (dissolved 1 part Venice T. and 1 part Turpentine). This mix might have been brushed on a dry layer and the following layer painted on the still wet Venice T. varnish. It is not specified if fully wet, we assume that it should have been allowed to dry slightly to become only tacky. The technique should facilitate the fusion of colours and edges, blending edges enough to give the picture a more harmonious effect. The same authors claim that Sir Peter Paul Rubens also used mediums prepared with Venice T. We could not confirm this.
Venice T. is often used combined with Stand Oil when a perfectly smooth flat gloss/vitreous finish is desired. Both ingredients level themselves out over a matter of 2 or 3 days while drying, eliminating all brush marks. The dry finished picture surface resembles a polished enamel jewel.