Treatment conservation is aimed at stopping or delaying processes of deterioration, and/or improving the condition of art or artifacts, through direct intervention with the material fabric of the object. Because there's always a risk associated with treatment conservation, conservators always abide by ethics and guidelines laid out by professional organizations.
In general, conservators strive for:
- Minimal intervention
- Reversibility of materials and methods used
- Full documentation, including before and after treatment, and of all work undertaken
Treatment conservation is where the magic happens! On the left is example of unstable beadwork, vulnerable to further damage and loss. On the right, the same artifact after it's been treated and stabilized by a conservator using reversible methods.
Conservator: Shirley Ellis
This baby blanket (or quilt), approximately 100 years old, came to the Royal Alberta Museum from the Blood Reserve near Cardston, Alberta. Composed with a decorative quilted side and a thermal skin side for warmth, it must have been great for those cold nights!
The cotton quilted side was made up of vertical bands – some continuous and some formed of patchwork squares of colour in reds, yellow, beige and black. The thermal side was made from gopher skins attached to a flour sack ("Cardston, Alberta" is still printed on it!).
The blanket was saved over the years but suffered rodent and moth damage, plus overall soiling and distortion. It had been much loved but now needed some attention so it was brought to the Conservation Lab for treatment. The surface soil and detritus were removed with a combination of low suction vacuuming and tweezers. After colourfastness testing, it was determined that it could be safely wet-cleaned but the layers needed to be separated. Not an easy decision, because even though conservators try to reassemble an artifact as it was originally, it can be difficult to recreate it exactly as it was, resulting in some change. We have to weigh the pros and cons. In this case, it was decided that the benefits of wet-cleaning outweighed the separation of the layers and possible change in reassembly.
First the weaknesses (holes and tears) of the quilt top were protected from further damage by encasing with netting. Wet-cleaning took place in a shallow sink using an anionic detergent called Orvus WA Paste (this detergent is used to clean large animals and contains no additives such as perfumes, colourants or builders). The suds were gently moved through the textile using a natural sponge with an up and down motion, followed by many rinses with purified water. Drying by pinning out on a drying board with a fan to circulate the air above it, allowed it to dry quickly and very flat, eliminating any use of an iron. No ironing, because the heat from the iron causes damage to the fibres.
Subsequent stabilization of the quilt top was carried out using compatible fabrics – the losses and tears were backed with similar colours and where possible and like fibres. This achieves two goals, the quilt top is stable and can be handled more safely, plus it is more aesthetically pleasing to the viewer by making it more complete, easier to read and enjoy. There was no intention to recover or replace the damaged areas (not a restoration but a conservation), the original material is still there and easily seen if you look closely. Even those patches that are patterned were only backed with a solid colour of fabric.
The next step was to treat the skin side of the quilt. The skins were distorted and attached to a very soiled cotton fabric. If wet-cleaning the fabric was to take place, the skins needed to be separated from it. Again, this decision was made with much thought and deliberation, followed with curatorial consultation. Clean textiles are more stable in the long term because the soiling and staining can cause overall and localized deterioration; plus the acidity is reduced, becoming more neutral.
The distorted skins were humidified and flattened through a controlled process. Once damp and pliable, they were manipulated with the fingers then weighted with light weights or pinned out (using existing holes) to flatten. Because there were losses in the skin layer it needed overall support to be able to work with it as one layer. This support needed to be as invisible as possible. Nylon tulle (wedding veiling) in a tan colour was chosen for this purpose. Once attached to the tulle the skins could be reattached to the now clean flour sacking.
Finally the two layers, quilt and skin, were reassembled using the original thread stitching in the original holes. In the end it is more stable, its appearance improved, its life span increased, making the baby blanket accessible for generations to come.
Content: Alison Fleming
While the other parts of the ensemble were in good condition, the choker had a number of broken and cracked beads, primarily along the top edge of the collar. Interestingly the affected beads were all white and had attracted noticeably more surface dirt than the others. We examined the beads under the microscope and discovered that the broken ones had a waxy, crumbly texture, and were oily. This strange softening of the glass generally began at the side of the bead nearest the canvas backing or from the inside of the holes. Beads that were degraded were also frequently located beside each other.
The sort of seed beads that were used to decorate the choker are known to sometimes suffer from glass disease, which is caused by incorrect proportions of basic "ingredients" in the glass mixture. If an excess of flux (compounds used to lower the melting point and improve the working properties of molten glass) is added during manufacture, the final product can be unstable. Elements in the flux are attracted to water molecules in the atmosphere, so may leach out of unstable glasses in humid conditions. This makes the surface very alkaline, even more attractive to water molecules, and the glass itself become more porous due to the depleted flux. Tests confirmed that the liquid on the degraded beads on the choker was quite alkaline.
Glass disease progresses in stages and can be visually identified by wet-looking surfaces, crystalline deposits and, eventually, cracking and breakage. The beads on the choker were waxy and squishy rather than crusty or fissured, though, so we wondered what was causing this. There have been some documented cases of degrading beads sewn to oily leather that have saponified (the same reaction that produces soap) due to contact with fats and, and so become waxy. This description sounded more like what was happening to the beads on the choker, but it was beaded onto fabric rather than leather, so how could the beads have come into contact with fats? Curator Ruth McConnell suggested that there might be residual bear or goose grease on the artifact, and Judy Half, the Aboriginal Liaison Officer at the museum, confirmed that there were indeed a number of possible uses of these substances that could have resulted in their being transferred to the choker and soaking into the fabric and thread.
We had a better idea of where the fats might have come from, but why were only the white beads affected? Blue, red and black beads are known to be particularly susceptible to glass disease, but white is actually a colour that is meant to be more stable. Were these beads simply from a bad batch, or was it an additional ingredient added to create the opaque white colour that weakened the glass? Glass "recipes" for individual colours can vary, so we hope to have the composition of these specific beads analysed in order to get a better idea of what happened.
Unfortunately, once it has started, glass disease is irreversible. It can be slowed by removing the degradation products and getting the pH down to a level where the degraded beads will not "infect" healthy adjacent ones. The crumbly, mushy beads were removed, and the beading, and as much of the canvas backing as possible, was cleaned under the microscope using small shreds of fine non-latex sponges, which picked up a lot of oil and dirt. The beads were then cleaned with ethanol on swabs. This treatment neutralized the pH of the beads, and slightly lowered that of the other elements. We did not replace the diseased beads, as their absence did not disrupt the pattern on the choker (luckily they were the background colour) or interfere with how viewers might interpret the object.
The progression of glass disease can also be slowed by storing objects at a relative humidity of between 38 and 42 % with very little fluctuation and lots of airflow. Unfortunately, these exact environmental targets are very difficult to maintain in storage and in exhibition, and even if the outfit were kept at these specifications in a sealed case, this relative humidity would not be good for some of the other materials used in Samson's regalia. Conservators and curators often have to weigh up the pros and cons of putting sensitive artifacts on public display, as factors such as light, imperfect temperature, and humidity will invariably shorten their "lifespans". We did consider not displaying the choker, but it is an integral part of an important ensemble, so it will be put on exhibition for now and its beads monitored carefully.
Case Study 3: Materials Analysis
Content: Carmen Li
Conservators are often asked to help with materials identification and analysis to help curators better understand and interpret the objects in the museum's collection.
This is a piece of surgical furniture – an examination table—that belonged to Dr. M.E. Mackay, surgeon at the Royal Alexandra Hospital from 1910-1928. Originally a varnished wood, the table has been over-painted with a glossy off-white paint at some point in its history, to "modernize" its appearance. But when, precisely? Was it a historic application, or far more recent? One theory was that Dr. Mackay could have applied the over-paint himself in the 1920s, in an attempt to imitate the style of the enamelled surgical furniture that was coming into vogue then. Curator of Western Canadian History Cathy Roy asked if we could perform some technical analysis to determine when the over-paint was applied.
A paint is basically composed of a binder, a pigment, and a vehicle (also known as solvent, most commonly oil or water). Some paints contain other additives as well. Commercial paints as we know them today first became available in 1875 with the invention of the now ubiquitous paint can. Early commercial oil-based paints were made with naturally derived binder, most commonly linseed oil. Acrylic resin paint was invented in 1934 but did not become widely available until around the 1950s. During the 1960s, alkyd oil binders derived from soybeans or safflower oil became popular.
Paint formulations also changed over time when it came to pigments. Prior to the 1950s, lead compounds were used almost exclusively as a white pigment or an opacifier (the pigment was known as lead white). In 1916, titanium dioxide became available as a pigment (titanium white), but it did not become prevalent until the mid-20th century.
So to try to date this paint, the first clue would be the binder. Another clue would be pigment or pigment combination that was used. Taking some very small samples from existing areas of paint loss, we asked the University of Alberta's Chemistry lab to analyze the flakes using Fourier Transform Infrared-microscopy. The absorption spectra from FTIR can help determine what kind of binder the paint is composed of. We then asked our colleagues in the RAM's archaeology department to analyze the surface of the artefact with a portable XRF unit. Since XRF is a technique for elemental analysis, it can give clues to the pigments used in the formulation of the paint.
So what's the verdict? We'll reveal that in Part Two, after the XRF results are in.