Paints and Pigments – When Art and Science Combines

The following post is by Lieselotte Dubert, Intern, Preservation Research and Testing Division. They are a rising Junior at Vanderbilt University, pursuing a double major in Mathematics and Studio Art.

This summer, I had the pleasure of interning in the Preservation Research and Testing Division (PRTD) at the Library of Congress working with their colorant reference collection. PRTD has a collection of over 500 pigments and dyes within their collection of reference materials and samples. The pigment samples in PRTD’s collection come in every color imaginable; their sources cover natural materials, like flowers and rocks, to modern synthetic pigments. This collection represents artist materials that have been in use since antiquity right up to materials in use today. It is a truly impressive collection.

PRTD uses their pigment reference collection to gain historical understanding and scientific information about the materials. They are used with non-invasive instruments to collect data about the pigment’s qualities and makeup. This information can later help them with identifying the materials used in collection items, by comparing the data they collect from that item with the reference data they collect from these pigments.

PRTD makes these reference pigments into “paint outs.” Paint outs are small cards on which swatches of various types of paint are laid out for study. The different paints used in these cards are created by mixing pigment with various substances used to bind the pigment particles together, called binding media. The binders used for most of the paint outs are chosen to be broadly representative of historic materials, in order to provide a representative set for the ways in which the pigment may appear in other artifacts PRTD studies. The set I worked with used six binders: gum Arabic, glair, egg tempera, rice starch, acrylic, and linseed oil.

When I began my internship this summer, PRTD had around a hundred pigments already painted out with most of the binders. Most of the cards were only missing the linseed oil patch. My first goal of the summer was to complete these cards and their data sets.

This meant many hours spent grinding pigment powders into the oil medium to paint the last little squares on all of the cards. It was satisfying to be able to finish these. After completing the painting, it was time to round out the characterization and I did some Fourier-transform infrared spectroscopy (FTIR) and fiber optic reflectance spectroscopy (FORS) to fill in the gaps in the spectral database of these materials. I also took microscopy images, which can be helpful in identifying visual characteristics of individual pigment particles.

The most exciting part of my internship so far is when I started making new paint outs for pigments that had not been done yet. This meant I was able to work with the full range of binders and a wider array of pigments. As an artist, I was already familiar with some of the paint types from my many years of painting, but I had only ever worked with pre-made paints in tube form.

It was interesting to see the process through which the colorful powders became familiar paints and to be able to recreate them myself.

The overall goal of creating the paint outs was for their use in further scientific research, but the process of making them was just as intriguing to me. While my experience with the modern versions of these mediums and colors is not fully applicable to the historical recipes and procedures, I found the overlaps that did exist were personally enlightening. During the process of making and using the paints for their samples, my attention was focused on physical or artistic qualities like the color’s vibrancy and the paint’s texture, like I would any time I paint a picture. But working with the paint outs to collect data afterwards connected these ideas to the things that PRTD looks for in their research for preservation, like the pigments’ lightfastness and stability.

It was the aspects of art and history in this paint out process that initially caught my interest, but I also appreciated the opportunity to contribute to PRTD’s ongoing research of these materials and their qualities. PRTD does priceless work for studying and preserving pieces of our history and I am glad that I was able to take part in even a small portion of this endeavor. I had a wonderful time working in the Preservation Research and Testing Division and I am grateful to Tana Villafana and Cindy Connelly Ryan for all the time and effort they put into making this such an exciting and educational experience for me!

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