R. Gamblin Conservation Colors are made from Laropal A-81, mineral spirits, and lightfast pigments. Alumina hydrate is added to the modern organic colors to adjust tinting strength. No additives are used.

Color Notes:

• Opacity and transparency information provided for all hues.
• Lightfast alternatives formulated for Indian Yellow, Alizarin Crimson, and Brown Madder Alizarin.
• Extender White is made from calcium carbonate (PW18). Use this to increase transparency, or translucency of a color without changing its viscosity.
• Black Spinel is made from a high temperature fusing of copper and chrome. Its tint is the most neutral of all black pigments.

The palette includes modern organic colors: Indian Yellow, Hansa Yellow Medium, Manganese Blue Hue, Dioxazine Purple, Quinacridone Red, Phthalo Blue, Phthalo Green.
Suggested use: when high chroma in a mixture is needed. Most of these colors are highly transparent.

The Transparent Earth Colors are made from hydrated synthetic iron oxides.
Suggested use: on old paintings made with natural earth colors more transparent than those available today.

Binder Notes:

Laropal A-81 is a synthetic low molecular weight resin, a urea-aldehyde resin. Its special characteristics are:

• photochemical stability
• excellent pigment wetting
• working properties similar to a natural resin medium.

After aging for 3000 hrs in a Weatherometer, solubility of the resin changed only slightly. The resin is soluble in solvents of low polarity both during working and when it is aged.

Note: Technical papers, the first of which will be published in October 2000 for the IIC Congress in Melbourne, will offer more specific details about the properties of the resin.

Managing the Solvent in the Color Jars:

There is no perfect container for solvent borne color systems. Tubes and jars lose solvent during working sessions and in storage. Gamblin Conservation Colors are packaged to allow a conservator to manage the solvent loss or to revive paint that has hardened.

• Assume that each jar of Gamblin Conservation Color will slowly lose solvent.
• Add drops of solvent periodically to the color jars to replace what has been lost.
• If the paint skins over from solvent loss, add two or three drops of mineral spirits or isopropanol into jar, let sit for an hour or two then mix to re-wet the dried paint.
• If the whole jar has dried, add solvent and mix until the paint has re-wetted thoroughly.

Note: Some conservators store solvent borne paints in air tight containers to slow the evaporation rate.

The solvent strength required for Gamblin Conservation Colors is lower than most other media used for retouching.

Solvents for in-painting with Gamblin Conservation Colors:

• When wet from the jar, dilute with aliphatic hydrocarbon solvents (mineral spirits).
• If paints dry on the palette, they require only a 25% aromatic mineral spirit to re-wet them.

By using two petroleum distillate solvents of similar evaporation rates (one of 100% aromatics and the other an aliphatic solvent), conservators can mix a range of solvents with specific evaporation rates and solvent strength.

• For crisp brush stokes use a faster evaporating solvent.
• For more working time use a solvent with a slower evaporation rate.

A few suggestions from conservators on solvents to use with Gamblin Conservation Colors:

• (1:1:1) mixture of petroleum benzine, Shell TS-28, and isopropanol
• (1:4) mixture of isopropanol in mineral spirits (15% aromatic)
• Isopropanol

Gamblin Conservation Colors dry fairly matte.

• To keep the gloss level low, dilute the colors with small amounts of solvent only.
• To increase gloss, dilute the colors with Galdehyde Resin medium, the binder for the colors.

Formula for dry Laropal A-8:

• Use the resin jar as your resin mixing container. The resin weighs 65 grams.
• Add 74 grams of a petroleum distillate solvent of approximately 40% aromatics. (This is stronger than the strength of the solvent needed for in-painting because this resin solution is high in solids and it takes a stronger solvent to dissolve that much resin into a stable resin solution)
• Or, to make a petroleum distillate of 40% aromatics, add 32 grams of 100% aromatic petroleum distillate to the jar, then add 42 grams of a low or no aromatic petroleum distillate. 74 grams total.
• Shake the jar periodically to help the crystals dissolve. The resin solution will be complete when all of the crystals have dissolved.

Final Picture Varnishes:

Any varnish, utilizing the proper technique, can be applied over Gamblin Conservation Colors.

• Paraloid B-72 or other varnishes that are mixed in 100% aromatic solvents (or any combination above 15%) may disrupt the retouching if it is vigorously brush applied. Such varnishes may be spray applied.
• Regalrez 1094 or MS2A (varnish resins that can be dissolved in aliphatic solvents) may be brush applied over the Gamblin Conservation Colors.

Note: We strongly recommend testing varnishes and application techniques over the new retouching paints on a mock up before using them in a complete treatment.

An excellent resource on varnishes and varnishing that goes into detail on all the traditional and the new varnishes is: Painting Conservation Catalog, Volume 1, Varnishes and Surface Coatings, published in 1998. It is available from AIC 01-202-452-9545.

May 2000