Community: bloggers@brooklynmuseum

In my previous post, I discussed how an adhesive introduced with an ultrasonic mister can be used to stabilize paint layers. Now you can see that close up as illustrated here of another watercolor in the exhibition, Quarry by William Thon, ca. 1952 (pictured above). Much of our work is done under a microscope which magnifies the area we are working on enabling us to be more precise and to see things not visible under normal conditions. As we work on a piece we can take photographs through the microscope known as photomicrographs which are included below. In this watercolor the artist used a range of techniques to apply his paint including a brush and a sponge, and by pouring and dripping paint onto the surface, wet on top of wet layers. Unfortunately, some of these layers are not well adhered to each other.

In the photomicrograph above you can see the top layer of brittle black paint which is lifting away from the underlying powdery yellow paint. We used the ultrasonic mister to treat this watercolor which worked very well for consolidation of the powdery yellow paint, where it would have been otherwise difficult and time-consuming to introduce an adhesive with a brush. For some of the larger paint flakes it was necessary to use the more traditional technique of inserting the gelatin adhesive to specific areas with a minute brush under magnification. See the after treatment photomicrograph below where the black paint has been set down and is no longer lifting away from the yellow layer below.

In preparation for the Museum’s current exhibition, Brushed With Light, conservators in the Paper Conservation Department examined over ninety watercolors. It was great to work on familiar works as well as those never examined or exhibited before. A common condition problem we observed during examination was the presence of unstable paint layers. Watercolors consist of pigments ground in gum arabic, a water soluble gum usually from the acacia plant, which holds or binds the pigment particles together and allows the color to be brushed onto a paper support. There are numerous causes for the paint to become unstable and lift away from the paper, including an insufficient amount or deterioration of the gum binder which can cause cracking and if left untreated, can result in paint loss. Some artists painted their images thickly, squeezing paint right out of a tube to create raised areas of paint called impasto. These areas are vulnerable to loss due to expansion and contraction of the paper and to a lack of adhesion to the paper. Some artists occasionally mixed additional gum into their paint, or as a glaze on top to add saturation to areas of flat color. With age these areas can become brittle and tend to crack and loosen.

In this photograph, I am consolidating lifting and powdery paint on the watercolor, The Samuel Fleet Homestead by Frances Flora Palmer, from the 1850s. The watercolor depicts a house which once stood at the corner of Fulton and Gold streets in Brooklyn and was reproduced in an 1884 publication, History of Kings County and Brooklyn by Stiles.

The piece was previously attached to a stretcher and in the image above you can see it was darkened in the central area where it was once exposed to light. It had been treated extensively in the past, but recent examination under magnification revealed areas of lifting paint where the artist used additional gum binder to enrich shadows in the trees and foreground, and to add dimension to the horses and some of the figures.

To consolidate, or re-adhere the loose pigment particles and flakes, I applied an adhesive using this ultrasonic mister. Most of the time consolidation is done with an adhesive introduced with a very small brush under the microscope under one paint flake at a time. The advantage of the mister is that the adhesive—in this case a photo-grade gelatin in ethanol and deionized water—is formed into minute particles which are smaller than the pigment particles. Because of their size they are easily absorbed into the pigment without changing the appearance of the paint layer and can be applied to a larger area at one time. This is an incredibly successful and useful technique for stabilizing powdery paint and small, light paint flakes as with this watercolor. In this case I am carrying out the treatment on a suction table which creates a downward pull to further enhance the absorption of the consolidant into the paper.

In my next post, we’ll go under the microscope to see the before and after effects of consolidation with an ultrasonic mister on another watercolor in the exhibition.