Ann, thank you for raising this important safety concern.

Mercuric chloride (also known as corrosive sublimate) was historically used as a preservative to inhibit microbial growth in certain animal-glue preparations. However, this does not establish that it was commonly used in Russian gilding glue or that the particular product you…

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Theodore, thank you for sharing both your research and your work in progress. Your distinction between reconstructing a historical recipe and understanding what the materials made possible for Mantegna is important. The relationship between the support, its preparation, the binding medium, and the application of paint is fundamental to…

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Hi Mario,

Yes, there are studies on Regalrez 1094, but most of the published research concerns its use as a conservation varnish or saturating resin, rather than as a resin incorporated into an oil-painting medium.

Regalrez 1094 is a low-molecular-weight hydrogenated hydrocarbon resin. One reason it attracted considerable interest in conservation…

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Ann, there are several workable ways to produce a metallic gold frame without using genuine gold leaf, but the products you listed are not really equivalent. The important distinction is between metallic pigment suspended in a binder and a coating that merely has a gold-colored or pearlescent appearance.

The Schmincke product is what…

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April, I’m not sure which session Leigh is referring to, but the issue is the amount and type of oil that can transfer from the brush back into the paint layer.

If you rinse brushes during a painting session and then immediately return to painting, use a drying oil suitable for painting, and wipe the brush thoroughly before loading it with paint.…

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You definitely do not want to use “boiled linseed oil” to rinse brushes. This is linseed oil with driers. You can use drying oils during painting sessions and non-drying oils between sessions, when you can wash the non-drying oil out with soap and water. Non-drying oils, such as vegetable oils you buy at the grocery store or supermarket,…

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The next Cohorts is September 26. Please see the updated Cohorts page. You can always find the latest information on your dashboard.

Yes, you can continue using a thin couch of Oleogel for subsequent layers. The presence of a small amount of bodied oil in the imprimatura does not, by itself, make that layering method structurally unsound. Allow the imprimatura to dry thoroughly, apply only a very thin couch of Oleogel, and paint into it while wet. Avoid leaving an…

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The Cohorts sessions are all there on the Cohorts page, and links to the Technical Studio Sessions are all on the Technical Studio Sessions page.

Audrey, artists have certainly reused supports throughout history—by painting over failed compositions, using the reverse of a support, joining pieces, and mounting canvas or paper to rigid supports. The general practice of adhering canvas to a wall or panel is called marouflage and has been documented since at least the seventeenth century.…

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Yes, April. When using Rublev Colours Mounting Adhesive on a wood panel, my preferred method is to mount the prepared canvas directly to the clean, unprimed wood face. The back and sides—not the mounting face—can be coated with polyurethane to reduce moisture exchange.

However, acrylic gesso is porous and is not equivalent to sealing the panel…

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Audrey, the best practice is to stretch the linen temporarily, size it, and apply the ground before mounting it to the panel. Allow the prepared linen to dry thoroughly and stabilize before removing it from the stretcher. This avoids applying aqueous size and ground after mounting, because their shrinkage can exert considerable stress on…

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Apply Rublev Colours Tempera Ground on the ACM panel to prepare it for egg tempera painting. Rublev Colours Tempera Ground was specifically developed for use on ACM panels, but it can also be used on wood and other substrates. Here is more information: https://www.naturalpigments.com/tempera-ground.html

Read the article for some of the choices, but getting the exact one isn’t as important. It’s more about the pigment group in general, not matching a specific color.

No coarse lakes are avaiable today, and there are no good substitutes, but you can use Alizarin Crimson for lakes.

Read this article for more…

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Kimball, thank you for adding the corrected test photograph. It is helpful, and I do not think the streaking rules out voodoo or dry-down darkening. In fact, it may be part of the same phenomenon.

Dry-down darkening does not necessarily occur uniformly across an entire passage. While a solvent-rich paint film remains fluid, differences in…

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Kimball, the photographs, timing, and results of your white-paint test point most strongly to dry-down darkening, sometimes called “voodoo darkening,” possibly combined with some uneven sinking or absorbency. It does not yet demonstrate a defect in either the Claessens linen or the Richeson Titanium White.

Dry-down darkening occurs while the…

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The replay of the Technical Studio Session: Earth Pigments Masterclass has been posted:

Earth Pigments Masterclass: Why a Working Palette Still Starts Here

The Cohorts session on The Functional Earth Palette is now posted in the Cohorts page.

Mustafa, I would separate this into two related issues: true sinking-in and dry-down darkening. They can look similar, but they are not the same problem.

The darker, cooler, purplish shift in the flesh tint looks consistent with what we describe in the article Oil Paint Darkening: Causes and Fixes for Accurate Color Tints: …

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Susan, you are right to point out that line in the decision tree. It should be clarified.

The warning against alkyd primers is mainly directed at their use as grounds on flexible supports, especially stretched canvas. On canvas, the ground has to tolerate flexing, keying out, handling, transport, and sometimes cold temperatures. Under…

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Good question, Susan. The article distinguishes between alkyd primers as ground coats and paint layers applied over the ground. The article’s relevant warning is that alkyd oil primers are especially vulnerable as the sole preparatory layer on flexible canvas, particularly under cool handling conditions.

I would not treat the warning about alkyd…

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Hi Kristin,

Please accept my apologies for not replying sooner.

Yes, dewaxed shellac is a good choice for sealing raw wood panels before applying Rublev Colours Lead Alkyd Ground, provided the shellac is applied thinly, allowed to dry thoroughly, and lightly sanded before the ground is applied. Zinsser Bulls Eye SealCoat is commonly described as…

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