[George]

There are several articles on water-miscible oils in the Resources section you should first review. Once you have come back here and let’s discuss this further.

[George]

Unfortunately, nothing can impart structural improvement to oil paints containing dammar resin.

[George]

Cadmium sulfide pigments darkened when used with lead white upon first introduction to art, due to free-sulfur impurities in early forms of the pigment. This is not the case today because cadmium pigments contain only trace amounts of free sulfur. This may also have been true of early forms of synthetic ultramarine when it was first introduced in 1820, but is not the case today.

[George]

Ann,

For oil paintings, it is generally best to avoid commercial paint markers—such as Krylon or Molotow markers—when the goal is long-term permanence. Most of these products are formulated with acrylic resins, solvent-borne industrial paints, or alkyd systems designed for craft, signage, or mixed-media work. While they may perform well on many surfaces, their aging behavior in a traditional oil-painting structure is largely undocumented. The primary concerns are long-term adhesion, solvent interaction with the oil layers, and the possibility that the marker film may age differently than the surrounding oil paint.

If the halo outline will remain visible and will not be painted over, the safest approach is to apply it using oil paint itself, adjusted to flow smoothly enough for precise line work.

A few practical approaches that artists commonly use for this type of detail work:

1. Use a liner or rigger brush with fluid oil paint
Thin the paint slightly with a small amount of linseed oil or stand oil, and if needed a minimal amount of mineral spirits. The paint should flow easily but still retain sufficient body so the line remains crisp. A liner brush allows very controlled, continuous lines.

2. Use an empty marker body (with caution)
In theory, an empty marker such as the Molotow body you linked could be filled with oil paint, but oil paint tends to be quite thick and may not exit the felt nib, which can quickly clog the mechanism. These markers were designed primarily for acrylic systems. You would likely need a paint mixture with a relatively low viscosity and a stable suspension, which is difficult to achieve with traditional oil paint alone.

For icon work specifically, many painters instead use mahl sticks, ruling pens, or striping brushes, which allow very steady, repeatable lines without introducing unfamiliar materials into the painting.

One additional practical suggestion: if uniform width is critical, you may find it helpful to lightly guide the line with drafting tape or a compass guide and then paint the line freehand with a liner brush.

In short, for longevity and compatibility with the rest of the painting, it is best to stay within the oil-paint system rather than introducing commercial paint markers.

Technical Service

[George]

It is possible they used egg yolk in the gilded areas, but I am not knowledgeable about Spanish polychrome statutes. However, I know Sylvana Barrett, who taught gilding workshops at the Getty. She is featured as the painter in the video.

[George]

This is neither a historical recipe nor a good idea. Two reasons why: vinegar and mastic (or dammar) resin. May pigments are sensitive to acetic acid in vinegar, and resins become brittle and darken as they age.

[George]

Ann,

When working with metallic powders—especially bronze—it is important to consider adhesion, solvent sensitivity, and long-term stability rather than simply appearance.

First, regarding the underpainting: yes, it should be fully dry before applying the Schmincke Bronze Medium mixture. The bronze medium you describe is based on white spirits and coumarone-indene resin. It is a solvent-borne system, not an oil-based one. If you apply it over a still-curing layer, the solvent can soften or disturb the underpaint and compromise adhesion. Allow the underpainting to reach a firm, solvent-resistant dry state—meaning it cannot be moved or marked with light pressure.

For the undercoat itself, a simple oil paint layer bound in linseed oil is preferable. Avoid alkyds such as Liquin under the bronze layer. Alkyd films cure differently and can form a relatively closed, slick surface that may reduce the mechanical adhesion of the solvent resin bronze layer. A traditional oil paint underlayer—transparent yellow iron oxide or raw sienna, as you suggest—applied lean and allowed to dry thoroughly, is structurally sound.

Second, about using linseed oil to mix the bronze powder: I would not recommend it. Bronze powders are best dispersed in a solvent-resin system designed specifically for bronzing. Drying oil films encapsulate metallic particles differently and tend to dull the metallic effect over time. They also increase the risk of discoloration and uneven oxidation. The dedicated bronze medium exists precisely to control film formation and metallic sheen.

If the client wants the same visual character as the earlier works, then using the same Schmincke powder and its matching medium is reasonable. The coumarone-indene resin system is standard in traditional bronzing liquids and gives the sharp metallic brilliance you observed—often brighter than pearlescent mica powders, which scatter light differently and appear softer.

Your sponging method is acceptable provided:

• The underpainting is fully dry.
• The bronze mixture is prepared immediately before use.
• The layer is applied thinly to avoid solvent entrapment.

The mottled effect you achieved is largely due to variations in viscosity and uneven particle distribution, which can be recreated by deliberately under-mixing the bronze dispersion and controlling the application pressure with the sponge. That approach does not inherently compromise the film if the layer remains thin.

Regarding achieving an egg tempera–like separation effect in oil: you are correct that true tempera mottling results from density differences and rapid water evaporation. Oil does not behave that way. To approximate the effect in oil, you would rely on controlled scumbling, sponge application over a tacky yet set layer, or slight variations in the ground’s absorbency—not on natural pigment separation.

Given that you are now working on lead-oil-primed ACM panels, you have far more stable support than with the earlier stretched cotton canvas. Structurally, this is an improvement.

In summary:
Use a lean oil underpainting. Let it dry thoroughly. Apply the bronze powder in its intended solvent-resin medium—not in linseed oil. Keep the bronze layer thin. That approach will give you the closest match to your earlier works without introducing unnecessary structural risk.

Your instinct to practice the more elaborate Duccio-inspired surface work on smaller panels first is sound. The material discipline required for sgraffito and clay tooling is entirely different from that required for oil handling.

Best,
George

[George]

I answered your question in the article, since it is topical to its content.

[George]

I am curious where you read this information about chrome yellow? Much of the information about historical pigments is from previous centuries, especially the 19th century, for chrome yellow. Chrome yellow (lead chromate) was susceptible to sulfur dioxide present in air pollution, but in the 20th century, a type of lead chromate encapsulated in silica was developed that is resistant to sulfurous fumes. This is the type of lead chromate we use in our products.

[George]

The purpose of Lac Water Varnish is not so much to serve as an isolation layer as to act as a fixative. Watercolor is easily lifted when brushing over with more color or water. This makes glazing difficult and building up color depth nearly impossible. With Lac Water Varnish, you can fix the paint on paper and do multiple passes of paint. Lifting is not an issue with oil paint, so there is an equivalent of Lac Water Varnish in oil painting. Was there another purpose you were thinking about?

[George]

Stephen,
I am working on an article that provides detailed information on best practices for documenting artwork. I plan to have the article ready tomorrow.

If you are discussing backing boards for canvas paintings, we recommend a dual system: a plastic exterior (e.g., Coroplast) and matboard on the inside, facing the rear of the canvas. It can be either 4 or 8-ply matboard, but it is best to use one that is acid-free (buffered).

[George]

You can add gold pearlescent pigment to your medium and apply it, but pearlescent pigments do not imitate gold if that is what you are seeking. At best, it does provide a golttery gold-like surface.

[George]

You can see from their reply that Artifx, a French canvas company, uses zinc in its oil grounds. They state “titnaium zinc.” Artefex is a company in California that makes ACM panels, and their grounds, whether on ACM or canvas-mounted ACM, consist of Rublev Colours Lead Alkyd Ground.

[George]

You can slow the drying process by reducing the amount of black oil and replacing it with linseed oil.

[George]

We do not recommend applying any coating to the reverse side of stretched canvas paintings. Instead, the best practice is to use a backing board. There is an article about installing backboards on canvas paintings.