The Invisible Threats: Understanding What Harms Museum Collections

Image 2 shows New Brunswick Museum 2007.16.1, a wheelchair, Canadian, from 1900-1925. The woven cane seat had been damaged by pressure from above. This artifact underwent extensive conservation treatment to repair this old damage in preparation for the New Brunswick Museum’s 2018-19 feature exhibition, “Legacy of Victory: New Brunswick in the Wake of the First World War.” The left side of the image shows the wheelchair before treatment; the right side shows it after treatment.

Image 3 features New Brunswick Museum 1966.88.1, a New Brunswick rocking chair c. 1850. The stretcher and rockers are well worn with use. In the museum context, attempting a repair is not appropriate because this shows significant evidence of historic use.

Image 4 displays New Brunswick Museum A66.4 F, a gilded picture frame c. 1870. The gilding, or gold leaf, has been extensively worn off the horizontal surfaces. This is common on historic gilt frames and is often the result of years of overly aggressive dusting. The dark areas you see are not dirt, but exposed bole, or ground layer, where the gold leaf has been completely worn away.

Image 5 shows New Brunswick Museum A65.23, an earthenware dish, English c. 1780. This cracked ceramic dish has a very old repair with a metal staple. This was how valuable ceramic pieces were repaired in years past, before reliable adhesives were developed. The old repair itself is now of curatorial interest as part of the history of the artifact and so we would not choose to remove it.

The damage from direct physical forces can be quick and dramatic, such as when a dish slips out of your hands and shatters on impact when it hits the floor. It can be slow, such as when an object distorts due to the effects on gravity acting on it over many years. It also results from daily wear and tear when an object is used. Such wear and tear is considered evidence of historic use, and can actually be a useful source of important information that helps us to understand an object’s history. The Conservator must balance the goal of preserving the object while also preserving this evidence of use and change.

Image 6 shows New Brunswick Museum X16623.1-2, two carved figures attributed to John Rogerson, c. 1860. The figure on the left has been painted at some point in its history. Not all “vandalism” is done with the intent to cause harm. Museum conservators today view such overpainting of an object as inappropriate.

Image 7 features New Brunswick Museum 21942, a porcelain plate, late 18th century, Chinese. A unique accession number is carefully and discreetly applied to each artifact and specimen in the collection. Can you spot the accession number on the verso side of this porcelain plate?

Theft and vandalism are criminal acts and are concerns for all collections. Nearly as problematic are well intended but misguided or inexpert attempts to improve or repair an object or work of art. The result, from a conservation perspective, is almost the same as vandalism. But what is a “displacer”? Museums may have hundreds of thousands or even millions of individual objects in their collections. Museum staff must know the location of each of these at all times or else an object may become “displaced”. The multiple moves of the New Brunswick Museum collection over the years due to inadequate facilities have created more than a few unintentional “displacers”. In order to help limit the time and energy needed to resolve these issues, modern museum collection management standards require each and every museum object be assigned an individual tracking or accession number. You may have noticed tiny accession numbers written on an object that you have seen in a museum exhibit. Using this number, information about each and every object in the collection is carefully tracked on a database and continuously updated. That information includes the current physical location of each object, which helps to eliminate the displacement problem.

Image 8 shows New Brunswick Museum 22705, a porcelain dessert plate, probably English, before 20 June 1877. This plate was blackened by intense heat and soot during the Great Saint John Fire in 1877. It was found packed in a barrel at the remains of a house on Queen Square. In this case, the damage itself is a significant part of the curatorial importance of the artifact, because it is associated with a historic event.

House fires can result in catastrophic losses. They can happen in museums as well, and are probably the worst fate that can befall any collection or historic site. The world watched in horror as the National Museum in Brazil burned in 2018 and Notre Dame de Paris burned in 2019. Less well known examples happen regularly around the world. Fires will destroy most materials they touch directly, and those that are spared will nevertheless suffer extensive (though sometimes recoverable) damage  from the associated soot and ash deposits,  the heat and water, and the chemicals used in firefighting efforts.

Image 9 shows New Brunswick Museum 2003.16.86, a nine-patch silk quilt from Rexton, New Brunswick, c. 1850. At some point in its history, this quilt had gotten wet, causing the fabric dyes to transfer.

Image 10 features New Brunswick Museum 14598, a painted maple chest c. 1800 which is said to have belonged to Gabriel George Ludlow (1736-1808) first Mayor of Saint John. The top of this chest must have been exposed to moisture for a long period of time, causing the finish to bloom and deteriorate. Perhaps a houseplant lived here for many years.

Image 11 displays a couch, c. 1840. At some point in its history, this couch was exposed to a significant amount of water, which has stained and deteriorated the upholstery fabric and caused extensive damage. The dark line around the edge of the stain on the upholstery marks the point where the wetness stopped expanding. Dirt that was dissolved in the water was deposited along this border between the wet and dry areas of the fabric as it dried and the wetness began to recede. Conservators call this dirt deposit a “tide line stain”.

Next to fires, flooding is the single most destructive event that can befall a collection. Flooding can be a result of natural weather events such as rising rivers or heavy rain, or they can be accidental in nature, such as a plumbing incident. In the context of a museum, even something as simple as a slowly dripping pipe can put a collection at significant risk if it is not discovered and addressed immediately. Properly secured and adequate storage facilities combined with constant visual monitoring are effective preventive controls.

Image 12 shows New Brunswick Museum 1962.93, a chair, Canadian, 1790-1820. The lower part of the chair leg shows insect damage – flight holes chewed by the larvae of wood boring beetles. The left side of the image shows the chair leg detail; the right side shows the chair overall.

Image 13 features New Brunswick Museum 2003.16.83, a pieced and embroidered silk and cotton Crazy quilt from York County, New Brunswick, 1900-1925. The pink piece has most likely been damaged by insects feeding and leaving behind irregular shaped chewed edges on the remaining fabric. This quilt will also be used as an example in subsequent posts showing other agents of deterioration. The whole quilt has the same environmental history, but different parts are affected in different ways because of the chemical makeup of the materials.

Image 14 displays New Brunswick Museum 2009.38.63, a hide covered document box c. 1820. The hair is shedding, most likely due to insects having grazed on the hide at the base of the hairs, causing them to break off.

Image 15 shows New Brunswick Museum 1959.89.5.2, a Wolastoquey pouch attributed to Mary Aquin, made of ermine pelt with wool, silk cotton and glass beads, 1884-1888. Insect damage, including grazing, holes and fur loss. Notice how the damage is concentrated in an area that was covered by a beaded flap. Insect larvae feed most actively when they are protected from light. The image above shows a detail of insect damage; the image below shows the pouch overall.

Pests, such as certain insects and rodents, can do considerable damage to museum objects, particularly to organic materials (those with a plant or animal origin), such as paper, wood, natural fibre textiles, basketry, furs and leather. For this reason, museums must pay close attention to housekeeping, limit where food and drinks can be consumed, and monitor all collections areas regularly to watch for and record any evidence of infestation.

Image 16 shows New Brunswick Museum 1962.134, a mahogany chair, English, 1780-1820. Splatter marks on the chair legs were probably due to cleaning floors with a wet mop. This has caused accretions on the wood and, over time, caused green corrosion and pitting on the brass. The left side of the image shows the chair leg detail; the right side shows the chair overall.

Image 17 features New Brunswick Museum W319, an etching on wove paper of Fort Beausejour, Canadian, before 1939. At some point in its history, this artwork was in prolonged contact with a standard window matt. Most matt boards are made of wood pulp, which is naturally acidic. Over time, acidic vapors were released from the cut edge of the matt and absorbed into the paper of the artwork itself, resulting in the unsightly brown stain around the perimeter of the image. This phenomenon is known as “acid matt burn”. Window matts made of 100% cotton rag board, though more expensive, are a better choice because they are acid-free and will not cause this kind of damage.

Undesirable foreign materials are considered contaminants that should not come into contact with artifacts. These contaminants originate from various sources, such as dust, dirt, airborne pollutants, oils from fingerprints, acids from low-quality packing or framing, and cleaning product residues. The impact of different contaminants varies depending on the material. For instance, metals can corrode due to contaminants, moisture can be trapped against surfaces leading to mold, and even dust can attract damaging pests. Frequently, contamination results in gradual and continuous deterioration over extended periods.

Image 18 displays a cellulose nitrate talcum powder box lid from a private collection, exhibiting deterioration starting at its sharp edges. Early plastics like cellulose nitrate, frequently used to mimic costly natural materials such as ivory and tortoiseshell, possess inherent instability. Due to their chemical makeup, these materials will inevitably degrade over time.

Image 19 features New Brunswick Museum 2003.16.83, a pieced and embroidered silk and cotton Crazy quilt from York County, New Brunswick, 1900-1925. Certain specific colours within the plaid patterned fabric have deteriorated due to chemical incompatibility between the dyes or the mordants and the fibres of the textile itself. Notice how adjoining fabrics in other colours on the same quilt are visually unaffected. We can tell this is due specifically to the inherent vice of the chemistry of this one fabric because the entire quilt would have been subject to the same Agents of Deterioration over time.

Earlier, we discussed the effects of contaminants on artifacts. Sometimes contaminants are not materials from outside, but are chemicals coming from within the artifact itself. In some cases, because of the materials an object is made from, or the way it was manufactured, the object is inherently chemically unstable. Conservators call these situations “inherent vice”, and such cases are among the most challenging preservation problems that Conservators must deal with.

Image 20 shows New Brunswick Museum 1965.39, a mahogany and mahogany veneer pot cupboard, probably British, 1800-1815. Belonged to Captain Allen Otty (1784-1859) and his wife Elizabeth (Eliza) Crookshank Otty (1798-1852) of Darlings Island, New Brunswick. Notice how the areas of this piece of furniture that faced a sunny window for many years have bleached to a pale yellow brown, while the areas that were not exposed to direct sunlight retain their original rich red-brown colour.

Image 21 features ED2007.8, a dress bodice, c. 1900. Silk fabrics manufactured in the nineteenth century were sometimes “weighted” with metallic salts in order to give them better “drape” and other handling properties that were desirable for dressmaking. Unfortunately this chemical processing makes the naturally light sensitive silk fibers even more vulnerable to damage from light as they age. Exposure to light has catalyzed the deterioration and resulted in almost total loss of the weft threads resulting in a dramatic, shredded appearance.

The New Brunswick Museum holds Smith’s Celestial Globe (12516.1), an English paper and plaster artifact from around 1850 seen in image 22. Originally varnished for protection, the globe’s varnish has irreversibly yellowed and darkened due to prolonged light exposure.

Light and higher-energy ultraviolet (UV) radiation damages museum objects at a molecular level. While UV light is not required for viewing color and is typically filtered out in museums, all light causes organic materials to degrade and colors to fade or shift. This damage is cumulative and permanent. Consequently, light-sensitive items are displayed under low light for limited durations and stored in complete darkness to minimize deterioration.

You may remember our article detailing the extensive conservation treatment of this object carried out at the New Brunswick Museum conservation lab in 2019 in support of our provincial partner, THC Heritage Branch, and the Bonar Law Common heritage site in Rexton, New Brunswick. Many of the wax flowers (like the one shown in this detail) had melted into the dried moss backing, deforming and exposing the paper support inside the flower. Wax has a relatively low melting point so it is easily damaged by an environment that is too warm. The left side of the image shows a melted wax flower detail; the right side shows the object overall.

Preservation of museum objects requires that they be stored and exhibited within stringent environmental controls. Heat catalyzes the chemical reactions that are responsible for all forms of deterioration. Cooler conditions are better for the preservation of most materials, and particularly sensitive materials such as early plastics and some biological specimens are actually stored at the museum frozen. Freezing is also a routine part of our pest control measures when materials come into the museum. We have to be especially careful in handling them during this process, though, as many materials become very brittle when frozen. Even worse than conditions that are either too warm or too cold are conditions that fluctuate dramatically over short periods of time resulting in unintentional physical damage.

Image 24 shows a late 19th century work table made of mahogany, basswood, and cedar. The veneer layer has cracked and bubbled on one end. This was probably caused by different rates of expansion and contraction in the different wood species due to fluctuating relative humidity (RH) levels.

Image 25 features New Brunswick Museum 2005.16.24, a mahogany and birch veneer table, Canadian, 1790-1800 from the Pickett Family, Kingston and Oak Point, New Brunswick. Marquetry inlay can come loose and pop off when environmental conditions fluctuate. Changes in relative humidity can cause the wood to expand and contract and cause the animal hide glues holding the inlaid pieces in place to become brittle and lose their adhesion.

A closely related but even bigger problem than incorrect temperature is the question of incorrect relative humidity. Relative humidity (RH) is a measure of the amount of moisture in a volume of air relative to how much moisture that air can hold at any given temperature, expressed as a percentage. The two are inversely proportional: when temperature goes up, relative humidity goes down and vice versa. Conditions that are too damp can cause insects to breed, mold to grow, metals to corrode, soluble dyes, inks and paints to run, and paper to curl. Conditions that are too dry lead to physical breakage as materials become more brittle. As with temperature, fluctuating levels of RH are even more problematic than steady but less than ideal levels. All materials expand and contract to some degree with changes in these environmental conditions which can lead to damage and deterioration.