Lightfastness testing — Tammy Y. Hong

Lightfastness Testing at Home

I conducted a simple lightfastness test of the watercolor palette I used in Plant Obituaries to predict the way my artwork will age and as a creative way to document the duration of the COVID-19 quarantine. The lightfastness of a pigment is its resistant to fading when exposed to light. According to the lightfastness standards set by the American Society of Testing Materials (ASTM), the categories for a pigment’s lightfastness rating can range from Lightfastness I (Excellent Lightfastness) to Lightfastness V (Very Poor Lightfastness). The lightfastness of art media varies and are tested with different methods in an environment with a controlled exposure to light.

For my watercolor experiment, I filled two paper supports with color swatches before cutting them in half - one half will be stored in a drawer and the other will be taped to my window for sunlight exposure. The color swatches will then be compared at the end of the experiment to determine the lightfastness of each pigment in the palette. A watercolor lightfastness test normally lasts 3-6 months. However, for my experiment in particular, I plan to leave my color swatches on my window while recording the weather everyday until stay-at-home orders have been lifted.

*It is December 2020 and American never really got over the first wave…

*Color strips on your right in both Plate 1 and Plate 2 were exposed to sunlight

left - Plate 1 (from top to bottom): 067 Skin Color, 052 Lemon Yellow, 025 Orange Red, 014 Vermillion, 017 Cad. Red Light (Hue), 143 Cerulean Blue, 145 Marine Blue, 149 Prussian Blue, 116 Hooker’s Green, 071 Yellow Ochre, 197 Pale Red, 065 Cad. Yellow (Hue)

right - Plate 2 (from top to bottom): 024 Yellow Orange, 076 Orange, 022 Alizarin Crimson, 032 Permanent Rose, 176 Mauve, 114 Permanent Green Light, 117 Olive Green, 092 Chrome Green, 194 Burnt Umber, 231 Payne’s Grey, 004 Ivory Black, Japanese sum-ink (not from set)

COVID-19 Quarantine Lightfastness Test

START: 04/19/2020 | END: ????? (weather and temperature last recorded on 06/30/2020)

Materials:

24 assorted watercolors: Noted Ingredients: 1. Arabic gum 2. premium pigment powder 3. dextrin 4. water
Japanese sumi-ink (not from set) | Noted Ingredients: 1. soot from pine or certain vegetable oils mixed with animal or fish glue

Experiment preparation:

Each swatch of watercolor was mixed with 8 drops of water. Sumi-ink - water was added after ink was ground on an ink stone to create drawing ink consistency and color density. Weather and temperature (in Celsius) will be recorded every morning.

Experiment variables to consider:

This was a used second-hand watercolor set. Possible contamination. Ink- stick consistency was subjective.

Data Collection: Forecasts

DURATION: 73 days

Organized and attended ASTM D01.57 Artists’ Materials Subcommittee Meetings at the National Gallery of Art, Washington, D.C. (2018 and 2019)

ASTM D01.57 published standards related to lightfastness testing:

D4303-10 (2016) Standard Test Methods for Lightfastness of Colorants Used in Artists’ Materials:

1.1.1 Test Method A—Exposure in southern Florida to natural daylight filtered through window glass.

1.1.2 Test Method B—Exposure in Arizona to natural daylight filtered through window glass.

1.1.3 Test Method C—Exposure in a non-humidity controlled xenon-arc device simulating daylight filtered through window glass.

1.1.4 Test Method D—Exposure in a humidity controlled xenon-arc device simulating daylight filtered through window glass.

Other published standards under ASTM D01.57 Artists’ Materials Subcommittee

*Pastel samples were prepared for an Arizona test. No images available to protect the privacy of supplier’s product manufacturing information.