Preservation in Archives

I went to a professional development day on conservation and thought that I could share some of the pointers. This is often something we have little time to think about, but I think the main thing is that is all comes down to common sense and does not have to cost too much for a little preservation. However, as we were reminded, nothing last forever! I found it particularly useful to have the correct terminology to describe issues.
These are my notes, so forgive their casual nature, but they might be useful.
10 Agents of Deterioration
1. Physical Forces
Shock, vibration, abrasion, gravity

2. Theft & Vandalism
Due to social and political issues.

3. Disassociation – lost items, or loss of provenance.

4. Fire
Heat, burn, smoke residue

5. Water
Particularly damaging to organic materials. Objects may swell. Paper becomes cockled, glue dissolves, pigments come out, tide lines, mould. There are mould spores in the air all the time and mould damage is one of the most difficult problems for conservators as staining is very hard to remove and spores always ready to reactivate. Also, water soluble dirt can have acidic by-products. Water causes metal to corrode which means that the metal or the elements in the metal are dissolving.

6. Pollutants/Contaminants
Sulphur and nitrogen compounds are in the air – more due to fossil fuels. Combined with water, this makes sulphuric acid (i.e. acid rain). Also chemical pollutants in furnishings and carpet – formaldehyde which can off gas and cause corrosion.
Need for air exchange so off gasses do not build up. i.e. display cabinets should not be air tight.
Wool and metal should not be stored together as the sulphur in the wool makes the metal corrode.
Contaminants can be liquid, gas or solids. e.g dust combines with moisture and attracts mould, salt on metals, tape – disfiguring stains, iron staining from nails or pins.

7. Pests
Good housekeeping – removal of food sources for rats and mice.
Carpet beetles, clothes moths – feed on keratin (hair, nails – wool)
Wood boring insects – larvae – like damp.
Mould – also a pest as alive. Needs food (i.e. dust), moisture (Relative Humidity of above 65% & oxygen).
Need suitable methods to remove dust – vacuum rather than wiping.

8. Light
UV – breaks down chemical bonds in pigment – makes some lighter and some darker.
Chemical degradation – weakening and brittle.
UV light – beyond the blue. Short wavelength so most damaging – can get inside object.

9. Incorrect Temperature
Not one temperature for all objects
Plastics – best at room temp.
Organic materials – suffer from expansion and contraction.
Quick changes in the range causes damage. If slow, the materials can expand and contract with little damage.
Passive methods of temp. control – buffering system – shelving, boxes.
Temperature and humidity interplay.

10. Humidity
Relative humidity – if this is too low organic objects become brittle.
Too high – metals corrosion. Salt effervescence – allows moisture to migrate through the object – weakens structure.
They recommended that we do a risk assessment of the collection to establish any problem areas and develop integrated pest management which involved use of natural rather than chemical controls, regular monitoring and recording and the quarantining of infested or new material coming into the Archives. They suggested isolating objects in plastic bags and also preventative freezing to kill any pests.
Altogether a most interesting session. I hope this is interesting to you too!

Robin

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