George's Blog

For liquid-type oil painting mediums, we recommend a mixture of bodied linseed oil, solvent and, as an option, a resin or blasam. Here are several formulas incorporating Canada balsam:

Canada Balsam-Bodied Oil Medium
3 parts Canada Balsam
1 part vacuum-bodied linseed oil
2 parts gum turpentine

Canada Balsam-Epoxide Oil Medium
3 parts Canada Balsam
3 part Epoxide oil
2 parts gum turpentine

The first formula will dry faster than the second, usually within an hour.

Canada Balsam-Black Oil Medium
Combine equal parts Canada balsam, black oil (linseed or walnut heated cooked with litharge or lead(II) oxide) and spike oil. Warm the ingredients to allow the Canada balsam to go into solution with the other ingredients. Mix a very small amount into your paint for easier handling and brushing. This mixture promotes interlayer adhesion and dries quickly. Keep covered to avoid excessive evaporation of the spike oil.

Heating vegetable drying oil with lead salts not only influences the handling qualities of oil paint but also its color. Lead white oil paint made with oil treated with litharge (lead(II) oxide) or lead acetate yellows more than that oil heated to 300° C without metal salts (Carlyle et al. 2002). This relates to reports in historical sources of the darkening of oil paint (Carlyle 2001b, pp. 23–4, 257–60). Oil painters in the past repeatedly complained of a ‘greasy layer’ that appeared on the surface of their dried oil paint and resisted further applications of paint. This was not confined to nineteenth-century painters (Carlyle 2001b, pp. 205–7, 229): the addition of spike oil to prevent an oily skin on the surface of blue oil paint is recommended in the de Mayerne Manuscript (1620–1644: folio 11r). This phenomenon has been observed in paint samples and is thought to be related to hand-grinding (which requires more oil than machine-grinding), and to the lack of suspension agents (such as stearates or hydrogenated castor oil), commonly used in modern paints. As we get closer to approximating historical paint recipes, we encounter technical problems familiar to painters in the past.

Essential-oil varnishes were used by the Italian and Flemish painters of the fifteenth and later centuries that were made from fir turpentine resins, dissolved by heat and adding an equal quantity of either petroleum spirit (naphtha) or spike oil, while the resin was in a liquefied state. This made a thin and glossy varnish, and was used as a protective covering for the colors in oil painting, to make them “hold out” without causing any of the disagreeable darkening effects, which are always caused by the use of an oil varnish when applied over a finished picture. Another advantage claimed for this use of an essential-oil varnish, was, that it permitted a repainting over it when dry, without any danger of cracking of the surface. Sometimes concrete Venice turpentine, the balsam product of the larch, was used in the making of this varnish, instead of silver-fir resin (similar in properties to Canada balsam). The latter, however, is more clear and colorless than the former, and is better than the darker Venetian turpentine.

Canada Balsam-Mastic-Copal Medium
The brilliance of Canada Balsam combined with the rapid drying rate of a soft resin and the hardness of the Copal concentrate produce a marvelous painting medium.

Ingredients:
2 parts Canada balsam
2 parts mastic varnish (44% resin w/v solution)
1 part copal varnish (44% resin w/v solution)
1 part vacuum-bodied linseed oil

1. Stir all the ingredients together in a double boiler over heat until the balsam combines with the other ingredients.
2. This produces a fairly heavy medium which can be diluted with turpentine or spike oil.

How to Use:
This medium can be thinned with turpentine and used as a final picture varnish. A. P. Laurie suggested that this painting medium very closely resembles the characteristics of the medium used by Jan Van Eyck (this has been not been substantiated by analysis). This formula dries in 1 1/2 hours.

Canada Balsam-Sun-Thickened Oil Medium
Canada Balsam both heightens the gloss of linseed oil allows a soft fusion of color glazes. Produces brilliant colors in the glazes. Fragrant, viscous, water clear and expensive, Canada balsam is worth every penny for it is unequaled in clarity and drying time.

Ingredients:
1 part Canada balsam
1 part sun-thickened linseed oil

1. Mixed over a double boiler, the heavy-bodied oil and balsam produces a clear, straw colored painting and glazing medium which can be safely diluted with turpentine although we prefer to use Lavender Oil of Spike.
2. Stand oil may be substituted for sun thickened linseed oil.

How to Use:
Mix the glaze with tube oil paints or with dry pigments. Apply it in thin coats. Rub it onto the painting with your fingers or with a rag (this is the best way to model smooth transitions in tone). A.P. Laurie spoke highly of Canada balsam, saying it closely resembled the legendary olio d'Abezzo or Strasbourg turpentine. Canada balsam with oil may be used for glazing or for painting the last thin coats over oil. A thin coat of this medium dries within 30 minutes. Venice turpentine, although much darker, performs somewhat like Canada balsam. It dries much slower.

Velatura Medium
4 parts Italian Varnish
2 parts beeswax
1 part gum turpentine
2 parts vacuum-bodied linseed oil
1 part Canada balsam

This medium gives your paint a translucent quality. The light can still transmit through it and bounce back from the underpainting and primer ground.

Venetian Glazing Medium
9 parts damar varnish (5 lb. cut)
9 parts turpentine
4 parts vacuum-bodied linseed oil
2 parts Canada balsam