When Ana Alba was working at the Hirshhorn Museum she undertook a research project on four paintings from Richard Diebenkorn’s “Ocean Park” series. Her study compared the materials used in each of the paintings and assessed how that tied in to their current condition. She presented her findings at the 2010 annual meeting in Milwaukee, Wisconsin. Two of the paintings had severe cracking while the other two were in good condition; the paintings with the cracking had an acrylic preparatory layer. At this year’s annual meeting she presented research conducted at the National Gallery of Art that expanded upon her intial study.
Ana’s current research involved the examination of more than 45 paintings and samples for analysis were collected from approximately 15 paintings. All of the information gathered was compiled into an extensive chronological database. An additional list of travel histories with photographic references was completed. The results of this study showed changes in the artists materials both between paintings and within individual works.
Diebenkorn worked for weeks to years on some of his paintings. He painted consistently on unsized cotton duck but his choice of preparatory materials fluctuated over time. Between 1968 and 1973 he used white acrylic gesso and toned it with diluted acrylic. In some cases he added alkyd. From 1973 to 1978 he transitioned from white to clear preparatory layers, presumably in order to maintain the raw canvas color and achieve transparencies in his paint layers. Scientific analysis suggested the clear material was synthetic and consistent with Rhoplex AC-33. This was more or less confirmed by photographic evidence of showing large jugs labeled as Rhoplex located in the artist’s studio. By 1979 Diebenkorn had returned to using acrylic gesso almost exclusively.
Diebenkorn primarily painted with acrylics and alkyds. He added oils sparingly and extended his paints as far as possible. He also used charcoal, graphite, and colored pencil to define his images. Infrared reflectography of his paintings show numerous alterations in his compositions, which is unsurprising given his appreciation of layering and the amount of time he spent working on each piece. Once a painting was finished he applied matte fixative to the surface. In his early works he applied this in 6 or 8 consecutive layers that left a glassy, heavy surface. Eventually he shifted his process and masked out the painting to limit application to the charcoal areas.
The condition assessment of this larger group of paintings seem to support the findings of Ana’s initial study. Paintings executed between 1960 and 1973 vary and some show some cracking. The cracks follow drawn lines, compositional changes, and are greatest on the paintings with heavy layers. Paintings completed after 1973 and before 1980 have heavier, more pronounced cracking with broad and isolated areas of cupping. These paintings follow the same trend as the earlier works with the greatest cracking located in the layered areas. Diebenkorn’s paintings after 1980 are in much more pristine condition with less cracks. The trend of this condition timeline show that the paintings in the poorest condition are located in the middle of the Ocean Park series. This supports previous findings by showing that paintings with Rhoplex and acrylic exhibit the worst cracking, especially when they are painted thickly with numerous layers.
This study highlights concerns regarding some of Diebenkorn’s selection of materials. Alkyds are brittle so putting them over flexible preparatory films and unsized canvas makes them susceptible to cracking from impacts and physical movement of the substrate. Fortunately, they do not seem prone to delamination so the cracking does not lead to significant paint loss. In addition, when Diebenkorn diluted his materials he reduced their strength. That left them with a greater chance of deformation in response to physical and environmental factors.
Ana pointed out that there are some limiting and extenuating factors to consider in this research. The are as follows:
- No samples were taken from privately owned paintings.
- His assistants did not see him working so they could not provide information about his process
- Diebenkorn did not keep detailed records of his work or do preparatory drawings.
- The study compares paintings in good and poor condition only.
- The artist destroyed some works, painted over others, and skipped #5 when creating the series.
- One large painting from Brooklyn was an outlier in the study; it was completed prior to 1973 but it shows significant cracking across large ares of the surface.