It is often assumed that modern collections, such as LHSA's HIV/AIDS material, do not need conservation treatment. However, this material is still vulnerable to deterioration because of its inherent qualities or inappropriate storage methods upon accession. Often, modern collections in archives consist of unstable or low-quality materials, as they were not designed to last but sewere intended for practical and temporary use.
For example, modern paper made from low-quality materials may exhibit greater deterioration than an older paper object made with high-quality rag paper. Plastics formed 20 years ago may already be fading or becoming brittle, and modern materials such as VHS and audio tapes could be unreadable after just a few decades.
Problems can also arise with mixed media collections regarding how to store these items together in their original form without losing their meaning, while still adhering to conservation standards. Ethical issues also emerge, such as which items to retain and which can be disposed of. Questions about conserving modern materials will only grow as more modern ones are produced daily, making this a new and fascinating area.
Conservation of
modern paper
Deterioration of
modern paper
Often paper made in the past 50 years shows greater
deterioration than papers made 500 years ago. For example, this newspaper page
(right) found in the HIV/AIDS collection has discoloured and become brittle.
Paper
deterioration can be caused by both internal and external factors.
Internal causes of paper deterioration
The raw materials and the manufacturing process of paper can
cause degradation.
Raw materials
In Europe, early papers were made from cotton, linen and hemp
rags which were relatively stable and generally made good quality papers.
However, as the demand for paper grew, papermakers began to use different
materials and methods which resulted in lower quality sheets. In the 1840s, a
method was developed for using ground wood pulp in the paper making process.
This type of pulp contains lignin which is acidic and darkens on exposure to
light.
The use of new materials, such as recycled fibres, optical brighteners and colourants and new manufacturing processes from the 1980s onwards has increased the types of paper available. However these processes and material all have an effect of the longevity of the paper and a paper conservator must be aware of the methods of production to successfully treat objects made from modern paper.
Manufacturing process
Early papermaking was all carried out by hand, which resulted in
a good quality strong sheet. However, it was a long and laborious process and
many sought to mechanise the manufacturing procedure to increase production.
The
first papermaking machine was invented in 1798 by Nicholas-Louis Robert. This
mechanical pulping and formation resulted in shorter fibres and also
unintentionally introduced metallic particles into the paper resulting in a
weaker sheet.
Chemical
pulping was introduced in 1854 by Hugh Burgers and Charles Watt. Chemical
pulping removes lignin and does not cut up the fibres as much as mechanical
pulping, resulting in a stronger paper.
From
the mid-1970s thermomechanical pulping was widely used. This method uses heat
and mechanical pulping to soften the wood chips used in paper making. Today,
the sulphate process is most commonly used to produce paper. This is a chemical
procedure in which wood chips are treated with sulphurous acid under high
pressure to produce cellulose and extract lignin.
Alum rosin sizing was introduced in the early 18th century in an attempt to strengthen the paper; however, this sizing caused further acid to form within the paper. Wood pulp paper from before the 1980s also tends to be acidic due to the alum-rosin sizing used. The development of synthetic sizing in the 1980s enabled the production of paper with a neutral to slightly alkaline ph. This, combined with a calcium carbonate filler, acting as an alkaline reserve to prevent acid contamination from the environment, resulted in paper with better ageing characteristics than modern papers from the early 20th century.
This resource by the Robert C. Williams Museum of Papermaking provides a good overview of the history of papermaking around the world:
External causes of paper deterioration
Environmental conditions
Temperature: high temperatures increase chemical reactions. An
increase of 10 degrees C doubles the reaction rate. Therefore, a cooler
environment is preferred for paper collections.
Humidity: moisture in the air can also accelerate
chemical reactions. High levels of humidity can aid mould growth and encourage
pests. Equally, low levels can cause desiccation of the object and result in
increased brittleness.
Fluctuation of these conditions causes the material to expand
and contract. Over a long period of time, this can weaken the physical bonds
within the paper and cause a loss of strength.
Pollutants
Gaseous pollutants can originate externally from industrial and
vehicle fumes, or internally from common materials such as paint, plastics,
cleaning supplies, and photocopiers. These pollutants, especially when combined
with a humid atmosphere, can initiate chemical reactions that can result in
paper degradation.
Light
The absorption of energy from light can trigger chemical
reactions that degrade paper. UV light is particularly damaging as it has more
energy than other longer wavelengths of light. Light can cause the lignin in
paper to darken and cause inks and dyes to fade. Other forms of light such as
direct sunlight and infra-red bulbs can also produce heat which again causes
paper to degrade.
Handling and storage
In the HIV/AIDS collection, the majority of the damage to the
paper documents is due to poor handling and storage during use, prior to
accession. They were often used in offices and, as such, not handled with great
care as they were just seen as ephemeral documents.
Paperclips and staples
Frequently, metallic paper clips or staples are used to hold
loose sheets together; however, these can rust over time and cause planar
distortion of the paper. These damaged areas now represent an area of weakness,
which will be more susceptible to damage over time.
Creasing
Due to inappropriate storage and careless handling, papers can easily become creased. These creases weaken the paper fibres and may be more likely to tear in the future. This is often caused by inappropriate storage. For example, documents placed in a ring binder may exhibit tearing around the hole punches.
Tears
This is often caused by inappropriate storage. For example,
documents placed in a ring binder may exhibit tearing around the punched holes.
Surface Dirt
Although it may seem innocuous, surface dirt can absorb
pollutants from the atmosphere. These can then migrate into paper and increase
the acidity of the paper. Surface dirt can also provide a food source for pests
and encourage mould growth. Without appropriate storage, dirt can accumulate on
the paper surface and result in paper degradation.
Conservation of
modern paper
Surface Dirt
Surface dirt has been removed using a chemical sponge. This
method was chosen as it is quick and easy to prepare. It can also be used to
target specific areas and is very effective at removing surface dirt
Removal of metal fasteners
In the HIV/AIDS collection, metallic fasteners such as paper
clips and staples are frequently used to hold together loose sheets of paper.
These items are all being removed to avoid the transfer of rust from the
metallic fastener to the paper. Care must be taken to avoid the tearing of the
paper during removal.
Once
these metallic fasteners have been removed, the nature of the object has been
slightly changed and it may not be obvious that these items were previously
held together. Therefore, simple paper tabs have been created to hold items
that have had their metallic fasteners removed together. The number of metallic
fasteners that have been removed has also been recorded so that the original
appearance of the items can be recreated if necessary.
Creasing
Creasing has been reduced by gently rubbing the creased area
with a bone folder over a piece of Bondina™. In some cases of extreme creasing,
the paper has been carefully folded back on itself to help the fold lay flat.
In most cases, the papers have been laid flat in the archival folders so that
over time they will lay flat due to the weight of other paper items on top of
them. In cases of extreme cockling, paper items have been placed in a press
between layer of Bondina™ and blotter to reduce planar distortion.
Tear Repair
Tears have been repaired using Japanese paper and wheat starch
paste.
Rehousing
All paper items are being rehoused into more suitable enclosures
to provide better protection from mechanical damage and to avoid migration of
acids from non archival storage methods.
Due
to the size of the collection, it is not feasible to house each sheet
individually. Instead, loose papers at a maximum depth of 2 cm are placed in
triptych folders. These folders are then placed in acid free clam shell boxes.