The Modestini Varnishing Technique
A Varnishing Technique Used by Mario Modestini
By Dianne Dwyer, Paintings Conservator.
Presented at AIC Philadelphia, 2000 at Paintings Specialty Group Meeting
After cleaning, etc., the surface of a painting is brushed with Talens Rembrandt Retouching Varnish (Laropal K 80 in white spirit). This thin varnish can be diluted with purified turpentine or mineral spirits, or made more viscous by adding Talens Rembrandt Picture Varnish, the same resin in a higher concentration, depending on the absorbency of the surface. Usually just enough varnish is applied so that the colors are sufficiently saturated to match when retouching. After the retouching is complete, any matte areas are brought up to surface gloss by locally varnishing with either the medium, PVA AYAB in alcohol (the Union Carbide resin which is no longer produced) or the substitute, PVA Mowilith 20, or with retouching varnish.
The surface is then sprayed with a solution of PVA AYAB or PVA Mowilith 20 in alcohol and acetone. (Note: these resins do not dissolve easily in ethanol. Usually they are are dissolved first in acetone and then diluted with ethanol. If the solution becomes slightly cloudy when diluted in ethanol, add a little acetone. Common hardware store denatured alcohol dissolves the resin easily.) The solution is approximately 5%. It can be checked by painting out on the fingernail where it should leave only a slight gloss when dry.
This is sprayed on the surface, a light spray, a few times. It dries almost instantly. If it leaves resin dust on the surface, the gun is too far from the surface or the air pressure setting is too high. On the other hand, the varnish should not wet the surface. As with any other spray, the distance and the amount vary with the size of the painting.
After twenty four hours, more or less, depending on the weather, the surface can be given a second brush coat of varnish, the viscosity chosen according to the characteristics of the painting and the surface desired. If necessary, these steps can be repeated to build up a third brush varnish.
One advantage of the technique is that the isolating spray provides a sort of floor, evening out different absorbencies of the surface, allowing a leached or damaged surface to hold a brush varnish, sealing up uneven cleaning which had to be suspended for some reason or left partially cleaned. It basically gives an evenly sealed, evenly absorbing surface and allows the conservator to apply a second or third brush varnish without picking up the previous varnish. As you know, this is otherwise not possible with any resin except mastic. Another advantage is that the restorations stay put; that is, they will not later either drop, become matte, or become glossier than the rest of the varnish.
If the final brush varnish is too glossy, it can be dulled with a spray of retouching varnish or a spray of fast evaporating solvent (trichlorethane, or preferably, a less toxic equivalent) containing a small amount of white bleached beeswax (a disc of beeswax about the size of a dime, in six ounces of solvent). After a few hours the surface can be polished, which will make it shiny but not sticky looking; or brushed fairly vigorously with a soft but firm dry brush, which will give it the look of an aged varnish. Alternately, a matting agent, wax or fumed silica, could be added to the final brush varnish.
In a survey of painting in eighteen Kress regional galleries completed a few years ago, paintings varnished using this technique had held up exceptionally well. After nearly thirty years, the surfaces had retained a pleasant sheen and the varnish had not noticeably discolored. (The varnish used was always Talens Rembrandt. The resin has varied over the years but seems always to have been a polycyclohexanone, e.g. AW2, Ketone N or, recently, Laropal K80.) By comparisons, paintings varnished a few years earlier by the same conservators using damar varnish showed significantly more yellowing.
The fact that the varnish showed so little discoloration over the years is partly due to the fact that the new varnish applications were minimal, another advantage of this method. Except in unusual circumstances, the total amount of varnish used was two brush coats of retouching varnish with a sprayed interlayer of 5% PVA AYAB.
By: Dianne Dwyer, Masterpiece Restorations, 434 East 52nd Street, New York, NY 10022
Studying and Conserving Paintings – Occasional Papers On The Samuel H. Kress Collection including a biography of Mario Modestini.