September 1998 Volume 21 Number 1

For the Birds: Conservation Treatment of the Bird Hall Diorama Murals in the Santa Barbara Museum of Natural History

The Bird Habitat Hall was created in 1960-64 at the Santa Barbara Museum of Natural History with the aim of depicting local bird species in local habitats. The background murals were painted by the noted Santa Barbara realist / landscape painter Ray Strong. Ray, now in his 90's, who went into the field and sketched the locations, made small scale mock-ups, and painted the background murals.

It was Ray's innovation to use asymmetrically curved walls to provide a flatter curved wall for the long view towards the horizon. In natural history diorama circles this was a major and controversial action but was quite successful visually.

Ray was born in Corvallis, Oregon on January 3, 1905. He knew he wanted to be a landscape painter by age 8. At age 19, he enrolled in the California School of Fine Arts in San Francisco. In 1926, he went to the Art Students League in New York, returning to San Francisco in '33. During the depression, Strong painted for the PWAP, and the CCC . He was involved, along with Maynard Dixon and others, with the founding of the Art Students League of San Francisco.

He was an active teacher of objective art during the ascension and dominance of abstraction, teaching at the College of Marin and organizing the Mendocino Arts Center. Strong moved to Santa Barbara in 1960 to become artist in residence at the Museum of Natural History and work on the creation of the Bird Habitat Hall dioramas.

The eight diorama murals that make three sides of the hall are painted on curved walls framed with 2x4's which were covered with diamond wire mesh. The diorama ceilings are made of a pressed board designed with holes in it to accept plaster. The walls and ceilings were plastered with a gypsum plaster in three coats. The join between the ceiling and wall, the cove, was built-up with much thicker plaster to a gentle curve. Acrylic ground was applied to the walls (reportedly four coats) followed by underpainting in acrylic and final work in oil paint.

In 1994 the dioramas, under the watchful eye of Exhibitions Curator Bob Dycus, were being considered for a conservation intervention to treat cracks that had developed in the plaster substrate. A particularly bad rainstorm, however, changed things. Water infiltrated through a leak in the roof/wall and through flooding caused by inadequate exterior drainage. The exposure to water mobilized epsomite (magnesium sulfate) salts present in the substrate plaster. Evaporation caused the formation of efflorescence and subflorescence in the murals. In addition to the fluffy salt growth that developed along cracks, there were hundreds and hundreds of hard, salt-filled blisters where the salt crystallized into a solid, dense mass below the paint and ground layers.

The walls were assessed twice by John Griswold and Bob Nishi using a Radiance infrared camera. The second examination, performed with a team of conservators (the authors, Griswold, Nishi, Leslie Rainer, Molly Lambert and Bob Dycus, the Curator), determined that the walls were no longer wet. Further, the conservation team agreed that there had not been any additional damage since the building envelope had been repaired.

Before conservation of the dioramas began, the roof was replaced. Funds were raised to improve exterior drainage, install a moisture intrusion alarm system, and to treat the diorama murals.

The EWA (early warning alarm) system for detecting water infiltration basically consists of two stainless steel wires in a woven polyester tape. The tape is glued around the perimeter of the structure or under the roof and connected to a central monitoring system. When water crosses the wires, it changes the impedance and triggers the alarm. [The system is so sensitive that when the crawl spaces behind the dioramas were recently sprayed for dermestids, the mist triggered an alarm.]

Treatment of the dioramas was complicated by the presence of the high concentration of epsomite in the plaster. Water based treatments could not be used for fear of causing further salt damage.

A mock-up wall was created and stressed to cause cracking. A number of different solvent based adhesives were injected by different techniques into the mockup. We found that of the limited number of adhesives we felt would be safe for the relatively young paint surface and the acrylic ground below, only Lascaux P550 performed adequately. Performance was assessed by cutting out sections of the cracks on the mockup wall and examining the degree of consolidation. To better visualize the adhesive, red Orasol dye and/or phthalocyanine blue were added to the adhesives before injection into the mock-up wall.

The diorama murals were documented with diagrams, photography, and Mylar overlays.

The areas that had been determined to require consolidation by injection were faced with Japanese tissue and a mixture of poly(vinyl alcohol) and Rhoplex N-580. The injection apparatus consisted of a modified caulking gun, a 60cc syringe, a 15 gauge needle, clear 1/16" polyolefin heatshrink tubing safety wired onto the needle, slightly smaller diameter (blue) heatshrink tubing, a section of 16 gauge needle, another piece of the blue heatshrink tubing, and a 5/64" diameter hole drilled into the void in the mural through the facing tissue. The key to obtaining a good connection to the wall was to insert the tip of the tubing into the hole in the facing/painting and then expand the tubing laterally by pushing the needle forward in the tubing without pushing the tubing or needle too deep into the wall. We found that this gasket system could withstand considerable injection pressure.

The syringe was filled with 20-40 ml of the P550 mixture (see below) and 10 ml of air. The pressure in the syringe was monitored by measuring the decrease in volume of the air. The air plug in the syringe also worked like a pressure reservoir. The adhesive was injected until it flowed out of 1/16" breather holes drilled 3-6" away from the injection site along the crack or hollow. The adhesive was allowed to dry under pressure applied with hinged paddles on 2x4 arms that were articulated to the work platforms. Weights were suspended from the 2x4 arms. After at least 48 hours, the area was inspected and retreated as necessary.

The hundreds of salt blisters were treated (in large part by Leslie Rainer): The blisters were faced locally; the blister was cut around on three sides; the facing, paint layer and ground were peeled back; salt and plaster were scraped from the reverse of the paint flake; salts and salt damaged plaster were excavated from below the blister; the back of the paint flake and the excavated wall were brushed with 20% Lascaux P550; the divot was filled with a non-aqueous fill; the paint flake was flapped back down; the area was lightly burnished (if necessary pushing excess fill out from behind the flake); and the flake was secured with a piece of tape. After a minimum of 48 hours, the facing was removed. Inpainting, as necessary, was done with Golden MSA colors.

Formulae

Consolidant:

• 35g Lascaux Acrylic Resin P550-40TB (40% butyl methacrylate in benzine)
• 7g VM&P naphtha with 10% Shell Sol TS-28 and 10% xylene added

Non-aqueous fill for sub-surface filling:

• 30 ml of a solution containing 15% Kraton G-1652 and 30% Regalrez 1094 in a solvent blend of 13 parts VM&P naphtha : 6 parts n-heptane : 1 part xylene
• 70 ml glass microballoons
• 10 ml fumed silica

Non-aqueous fill for surface filling:

• Above with 2-5 ml Golden MSA White (and other colors to achieve desired tone)

Suppliers / Manufacturers

Radiance® Infrared Camera (Portable Mid IR Camera; 3-5µ spectral response; 256 x 256 thermal array detector cooled to 77°K by a Sterling cycle cooler)
Bob Nishi, Regional Sales Manager
Raytheon (in Goleta)
tele: (805) 879-2250

Lascaux P550; Kraton G-1652; Regalrez 1094; Orasol dye
Conservation Support Systems
924 W. Pedregosa Street
Santa Barbara, CA 93101
tele: (800) 482-6299

Moisture Alarm System:
EWA (Early Warning Alarm) System
Ken Myrick
Hydro-Temp, Inc.
P.O. Box 418
Norco, CA 91760-0418
tele: (909) 371-8600
http://gtesupersite.com/hydrotemp