Conservation: Brushes of Greatness

Throughout my life, I have been aware of the importance of having proper artists’ tools. As far back as kindergarten, I recall feeling creatively stifled by the chunky, stubby crayons that the teacher supplied. How could I create a proper representation of anything, be it a face or a flower, with a waxy implement lacking a precision point?

In my professional practice of art conservation, it is particularly critical to have a wide array of good quality artists tools, made from the proper materials. Brushes are one of those supplies that must be well made and properly chosen, as their quality can make a big difference in the application of adhesives, coatings, and paints used in preservation. Inpainting a loss in the crack of a photograph requires a brush with a fine point, and a few hairs with the capability of holding just the right amount of pigment and water.

Brushes from Japan are used by conservators to mount brittle and damaged paper documents to a new support layer. They may be made from deer hair, horse hair, or goat hair, palm hemp,  or raccoon hair, depending on the procedure. These are the same types used for mounting the complex layers of Asian screens and scroll paintings. Other stiff bristled brushes are used for mixing water into paste to create the right consistency. There are some cheaply made mass produced brushes that occasionally have limited use. However, it is most critical to avoid a brush that is shedding bristles when pasting a lining attachment for a print or when reattaching flaking image media. The Japanese brushes cost over $100 each, so they must  be cleaned after use and stored carefully to provide a long working life.

Given my appreciation for fine brushes, I was fascinated by this catalog titled “Paints” from the Pittsburgh Plate Glass Company. First, some history about the company.

Pittsburgh Plate Glass was founded in 1883, and in 2025 they still operate as “PPG”, a brand change that occurred in the 1960s. They were the first successful plate glass business venture in the U.S. Around the turn of the century they acquired a paint making company, which increased their reach. It was a logical step, as window materials and surface finishes were marketed together. In the 1920s PPG produced roll up windows for the Ford Trimotor airplane and acquired Ditzler automotive finishes.

Once the paint business was fully incorporated, it makes sense that PPG would have branched out to brush manufacturing. The publication from the Hagley Library is far more than a product catalog. It provides mini histories of pigment, paints, and glass manufacturing, detailed  information about the craft of brush assembly, and the Pittsburgh Glass paint production process.  All sections are illustrated with halftones and color paint swatches provide a historical palette of the 1920s era.

The Pittsburgh Plate Glass catalog provides details on the different animal hairs. One section extolls how well badger hair is suited for the application of varnishes. The badger’s hair was described as soft, with great elasticity and tensile strength. Squirrel and civet hairs were used for sign lettering brushes. Hairs from different species were combined to make  brushes with desired characteristics and for budgetary reasons. Boar was, and remains, the source of bristle for stiff brushes. The process of dehairing hides, straightening, aligning and bundling the hairs had to be done delicately to preserve the natural points, which were critical for fine soft brushes.

.In this publication, the tail hair of skunks is called “fitch”, another name for the animal itself. This has been common nomenclature practice historically. Similarly, kolinsky is the name of an Asian weasel, for which high quality watercolor brushes are named.

Many of the wild animals relied on for these natural brushes are now species threatened with extinction. Some brush types may no longer be available, or may be quite expensive for this reason.  The use of nylon and polyester synthetic fibers has increased and may be a better choice for sustainability. They are preferable for acrylic painting, since the higher pH of this medium can break down natural hair brushes. To preserve natural brushes when they are not in use, they should be kept cool and dry. Treat them as you would a fur coat, which is likewise susceptible to insect damage.

If you have an interest in 20^th century paints, or the use of plate glass in construction and door fronts, Hagley Library has a number of other catalogs from the Pittsburgh Plate Glass Company. The collections include a report within the RCA records, regarding variable transmission glasses, an invention of PPG which provides sun protection built into eyewear.

Note: The embedded video link for the conservation of a traditional painted screen is from the Utah Museum of Arts, and shows the process of lining papers onto the artwork, using traditional brushes and methods. Layer by Layer: The Conservation of Chiura Obata's "Horses" Screen