Making Varnishes

The Making and Knowing Project has reconstructed varnish recipes several times, both as products and as ingredients in more complex making processes described in Ms. Fr. 640. The manuscript includes several recipes for spirit varnishes, which were a new category of varnish that emerged in the sixteenth century. It also includes several recipes for oil-based varnishes, which have a longer history and are quite dangerous to reconstruct and often result in fires. Accordingly, M&K is only sharing protocols for making spirit varnishes. Nevertheless, making spirit varnishes raises several safety concerns and may not be suitable for all pedagogical contexts.

Learning Objectives

The activity of making spirit varnishes has several potential learning outcomes, which can include:

  • learn what varnish is, what it is made of, and how it is made
  • exprience how various resins behave and appear in different alcohol and volatile oil solvents
  • understand how qualities such as viscosity were communicated through historical artisanal shorthands such as the “knife test”
  • explore the range of visual effects created by varnishes
  • understand material considerations that affect the appearance of artworks across history

What is Varnish?

A varnish is a transparent, protective coating most often made from resins in solution that, once applied to a surface, dries into a hard film. When applied to a painting, a varnish can help seal water-soluble and fugitive pigments, bring uniformity to the outer surface of the artwork, and impart an overall gloss.

Oil-based Varnishes

Until the sixteenth century, the most common varnishes applied over paint were oil-based or “fat” varnishes, made from resins of various kinds (e.g., mastic, sandarac, juniper resin, turpentine oleoresins, and colophony) dissolved in a heated drying oil, such as linseed, hemp, or nut oil. Such varnishes could have a yellow or green tint, depending on the oil that was used, and this tint could alter the perception of the painted colors beneath. This color alteration is often addressed in artist treatises, including in Ms. Fr. 640 on fol. 3r, where a recommended varnish “is appropriate for panel paintings and other painted things without corrupting the colors or yellowing.”

Spirit-based Varnishes

Over the course of the sixteenth century, spirit-based or “lean” varnishes were introduced into artisanal practice. These were composed of resins dissolved in alcohol or a volatile oil (such as spike lavender oil). They became common among painters because their underlying solvents imparted less color to the varnish. They were also easier and safer to make, requiring lower temperatures in their production. They also tended to dry quickly and have less viscosity or body, making them easier to handle.

Mixed Varnishes

In this period, there also existed a third, intermediary category of “mixed” or “semi-fat” varnishes, produced from oleoresins dissolved in alcohol or volatile oil.

Teaching Spirit Varnish Making

Spirit Varnish Making: Activity Sheets, Field Notes, and Resources

Varnishes in Ms. Fr. 640

There are dozens of entries in Ms. Fr. 640 that address the making and use of varnishes. In fact, “varnish” is one of the categories that M&K has used to classify the various entries in the manuscript, and entries on varnishes account for roughly 5% of the manuscript’s contents. These entries can be accessed through the “varnish” category filter in the List of Entries and by a wildcard search for “varnish*” to catch all instances of the term in Secrets of Craft and Nature in Renaissance France.

There are also several essays in Secrets of Craft and Nature in Renaissance France that explore varnishes in detail, including: