When things gets wet - dirt, mould, distortion, disintegration
Guest post by Alice Canon
January 18
Water is generally bad news for cultural collections, keepsakes and precious things. The floods in Queensland have the potential to cause a great deal of damage personal and public collections.
The water itself will permeate organic materials (wood, paper, textiles, leather) and begin to break chemical bonds. Though organic materials can be surprisingly resilient – you can immerse paper in water for some time without it disintegrating, for example – eventually the water will break things down. (That’s why we leave dirty dishes to soak). Additionally, some inks and dyes are water soluble and will bleed, causing staining as well as loss of image and information.
Inorganic objects (metal, stone, glass, ceramic) have a better chance but are not necessarily safe. Metal objects, particularly iron-based ones, can rust or tarnish very quickly when exposed to flood waters, especially if the water contains salts.
Water can also have a physical effect – I’ve seen water dripping from the ceiling create holes in a stack of paper below. Flood waters move fast, smashing objects against each other.
Flood water isn’t just water, of course. At the bare minimum it will also contain mud. There may also be oil, plant matter, general debris, agricultural chemicals, sewage, even animals. We’ve all seen the videos by now – if floodwaters can carry away a car or a house, they can carry pretty much anything. It can carry disease. All these various substances can also stick to objects. The damage caused may be chemical, physical or aesthetic.
It’s also important to remember that water will be wicked up by organic materials – so if boxes of books are standing in a puddle of water, the water will move up through the paper to a much higher level than the flood waters themselves.
And it’s not just the things IN the water that can be damaged. Queensland’s climate is ripe for mould growth at the best of times (warm, humid). As the flood waters recede and leave damp walls, ceilings & carpets, mould growth will blossom. Mould is most likely already growing in areas above the flood waters. (It doesn’t grow under water). Mould deserves it’s own post, so I’ll write more on that later.
Changes in humidity can also be damaging. Organic materials absorb and give out moisture to come into equilibrium with the surrounding air. So if the humidity increases, an object like a canvas, a chair or a book will absorb more moisture too. Its dimensions will change as the object expands or contracts. The canvas might shrink. (As the twisted fabric absorbs water it swells & tightens, causing shrinkage). The legs of the chair might swell. The pages of the book will curl. (This phenomenon is also why your windows don’t open so well during damp winter months).
Dimensional changes can put great physical pressure on objects. The effect is particularly bad if an object is made up of different layers. For example, a painting may consist of a wooden stretcher, a canvas tacked to the stretcher, a ground layer, many layers of paint (oil, acrylic, tempera) and a varnish. The wooden stretcher might expand when it takes on moisture. The canvas might shrink. The paint layers may not do much at all. So it’s fairly easy to imagine where all this might end up – twisted frames, paint popping of canvas and so on. The effect is worse when one or more layers are restrained, such as a canvas tacked onto a frame stretcher. And, if the object is dried too quickly, the same process occurs again as the layers shrink.
This all sounds very bad, I know, but keep hope – many things CAN be successfully salvaged after flood damage. More later…
Mould that has grown on books after water damage.
Cross-posted from pinknantucket’s posterous
Alice Cannon is a paper and photographic conservator who has worked in the US, New Zealand and Australia. She sometimes writes about conservation-related things at pinknantucket.posterous.com
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