Accumulation of Solid Particles on Documents, a Threat for Preservation of Documentary Heritage

Accumulation of Solid Particles on Documents, A Threat for Preservation of Documentary Heritage

The Example of the National Archives of India

by C. L. PRAJAPATI

introduction

Air pollution consists of various substances, and its composition differs qualitatively as well as quantitatively from place to place and region to region, even though some substances are present everywhere. The atmosphere of tropical and subtropical regions is often characterized by dust particles of silicon, soil and tarry organic materials. In the atmosphere of areas where volcanoes are active, factories vibrate and quarries are run, particles of lime, minerals and cement can be found. Smoke particles, generally produced by the incomplete combustion of coal, coke, oil, wood and rubbish, find their way into the atmosphere wherever there is fire. In heavily forested regions esters and terpenes are exuded from the foliage in vast amounts.

Terpenes are hydrocarbons and esters are reaction products of alcohol and acids. Both are aromatic organic aerosols, which often react adversely with organic materials. Chemical compounds such as chlorides, fluorides, nitrates and sulphates can cause chemical decay. Black smoke particles are essentially carbon, i.e. chemically inert, but being surrounded by oily and tarry products they may be quite acidic, thus causing embrittlement of organic material. Compounds of air pollution can also provide a suitable platform for fungal growth. Solid particles can act like sandpaper on files, books and manuscripts.

The size of such particles varies from 0.2 to 0.5 (µm. According to Stoke's law * of flowing bodies of a spherical nature, such small particles do not fall on the ground by their weight alone, but move randomly with every movement of air. They are carried by winds and storms, and on their way they bombard the surface of any object they meet. They enter buildings and accumulate over all exposed surfaces including books, volumes and files. The browning of the edges of

* Sir George Gabriel Stokes, physicist and mathematician, 1819-1903.

books is partly the result of this process. Solid particles suspended in air have a tendency to stick to the surfaces of objects they meet because of electrostatic attraction. Organic materials such as leather, textile and wood are most susceptible to such particulate deposits. Paper, parchment, palm leaf and birch bark are all equally affected by them.

purpose of this study

Various sources confirm the fact that there is no shortage of dust particles in the air of tropical and sub-tropical regions. In India, for example, in various repositories of archives, libraries and private custodial agencies located in the entire country, as well as the repositories of the National Archives, there is a good deal of dust deposited over the floors and shelves as well as over books and manuscripts. The author of this study, working as a conservation scientist in the National Archives of India (NAI), felt compelled to begin a study to find out the facts relating to the nature and accumulation of the dust in a repository in the close cycle of a year, in different regions. A first result, restricted to the repositories of the National Archives of India, is presented here. It is possible that it can be seen as more or less representative not only for the Indian sub-continent, but also for all big cities in tropical and sub-tropical regions. The findings may help to assess the grim situation caused by dust particles and to plan strategic measures for saving written cultural heritage against this ever potent and ever present enemy.

experiment

The building

The building of the NAI, constructed of grey stone, is located in the central region of Delhi, east of India Gate, near the crossroads of Janpath and Rajpath. Rajpath is a broad avenue, full of various kinds of plants and trees. Grassy land surrounds the NAI building, and rich vegetation would provide little dust creation, but the heavy rush of traffic is a rich source of smoke. Moreover, high winds carry dust particles from distant and more heavily polluted areas of Greater Delhi.

The old building (main building) has three and its annexe has six stack areas, each measuring at least 200 m2. Our study was confined to stack areas 2 and 3 of the old building and to 5 and 6 of the annexe, 3 and 6 being on the top of the respective buildings. In view of their large size the dust accumulation was studied in five partitions: in the east, west, north, south and in the centre of each repository, obviously 5 dust samples for each stack area and 20 in total.

Collecting the dust

Paper sheets of moderate size, i.e. 20 x 25 cm, were chosen as dust collectors and positioned as described for two months at a time over a year, i.e. for six periods, and weighed electronically before and after. The results are given in Table 1 and Fig. 1.

Additionally, dust particles from the NAI repositories on one side of Delhi and those from the libraries of Datia and Reewa (modern Madhya Pradesh, south-east of Delhi), a pollution-free area, were dissolved and dispersed in water, allowed to stand for half an hour and checked for distribution and colour:

• Dust from the NAI: A layer of black colour was deposited on the bottom of the dispersion vessel. A thin layer of black colour was floating on the surface.

• Datia and Reewa: A layer of brown colour was deposited on the bottom of the dispersion vessel. No layer on the water surface.

result and discussion

From Table 1 and Fig. 1 the following can be seen:

• Accumulation of dust particles was highest in the period March-May and lowest in July-September.

• The development of dust accumulation in the stack areas of the main building was similar to that in the annexe. The dust accumulation in stack area no 5 was in every period less than in stack area no. 6. NB: stack area no. 5 is situated below stack area no. 6.

• The development of dust accumulation over the year was similar in all the tested stack areas. This becomes quite clear from Fig. 1.

• The total dust accumulation of the year in stack no. 3 of the main building and in stack area no. 6 of the annexe is higher than the corresponding stack areas no. 2 and no. 5.

• The colour of the dust collected from the NAI repositories was blackish while that of the dust collected from libraries located in Datiya and Reewa was brown.

• Suspended in water and allowed to stand for some time, the NAI dust formed a thin black layer on the surface and the Datiya and Reewa dust did not.

These observations may be explained by looking at the rain in the relevant region. On the Indian sub-continent the months of July, August, September and October are normally considered to be the rainy season. December and January,

Table 1: Dust (mg) collected by sheets of paper of 500 cm2 over one year.

* Period of lowest pollution

**Period of highest pollution

sometimes, have winter rain but only a very little. March, April, May and June are considered to be the summer season, and the latter two months are marked

Fig. 1: Development of solid particle pollution over the year.

by high, scorching heat and storms. The Earth's surface becomes dry in this season and dust formation is a common feature. Due to storms and high winds, this dust is raised and carried far distances. Really, in May and June, the sky looks brownish instead of blue. Particles of different sizes, origin and nature gain access into buildings of all types through windows, ventilators and other such points if they are not closed.

In the middle of June, when there is some pre-monsoon rain, the pollution gradually decreases with an increase in rainfall. During July, August and September the region normally has heavy, intermittent rain, with the result that the accumulation of dust goes down to a minimum, but not to zero. After September, when the rain almost subsided, the rate of dust accumulation in the stack areas increased slowly up to January, as this period sometimes has rain (winter rain). After January a sharp accumulation took place up to May when it reached its hight.

The stack areas of main building at the NAI, have a covered verandah around them, while the annexe is devoid of such protection. Moreover, the stack areas of the main building are situated lower than those of the annexe. For lower floors, the rich plantation in the surroundings partly prevents the penetration of dust, while it is frequent in the annexe at upper stories. Significantly, the dust accumulation in the rainy season in the annexe was higher, but relatively equal to that in the main building.

The black colour of the dust collected from stack areas of the NAI clearly indicated that it included particles of organic character, among which there may be aromatic and carcinogenic hydrocarbons, anthracene, pyrene, benzene, soot and tarry substances, besides dust of an inorganic nature: obviously originating from the high air pollution in the city of New Delhi. This was confirmed by the black coloured floating layer on the surface of the aqueous suspension of the NAI dust. These particles were light in weight; they were neither suspended in the water nor settled to the bottom. In contrast, the colour of the dust collected from the libraries at Datiya and Reewan was brown. No layer of particles formed on the surface of the aqueous suspension. This dust did not contain any organic substances from pollution caused by urban traffic and industry, as the Datiya and Reewan are small cities and located in industry-free areas.

If pollution particles of any kind are not removed in time, a fair amount will accumulate on the surface of documents. During the rainy season the particles of organic nature will stick, making their removal by ordinary manual means difficult. If such particles are wiped with a cotton swab, cloth or sponge they will smear. If they are allowed to stay on the surfaces for a long period, they will give rise to fungal growth and /or to chemical decay of the substrate.

conclusions

The conclusions drawn from the facts reported above are that

• the rate of dust accumulation in the metropolitan city of New Delhi is very high and poses a threat for the life of documentary and cultural heritage;

• the nature of dust particulate matters of a metropolitan city is different from the dust of small cities which are not yet affected by air pollution;

• to save the cultural wealth against dust particulate matter, effective planning is needed in the region.

To find out the actual situation of dust accumulation in the entire Indian subcontinent, it would be necessary to conduct studies like that reported above in all the zones. The same is true for other regions and countries in the world. Efforts should be made to find out the constituents of the dust particulate matter collected from various areas.

Remedies

Our study demonstrates that the accumulation of dust from various origins in metropolitan cities is very high and that it provides a serious problem to docu-

mentary cultural heritage. In order to protect this heritage by housing in archives, libraries, graphic collections and other similar institutions, meticulous planning against the dust hazard is necessary. A two-fold plan must be prepared. Firstly, dust should be prevented from entering the repositories and secondly the accumulated dust must be removed periodically, from the stack areas.

The ideal would be to prevent the entry of dust completely. Quite often this is not possible, but there are means to minimize its rate. All windows, and ventilators, if there are these too, should be fitted with curtains of quality cloth able to attract dust. Of course, these curtains and cloths must be changed and washed regularly. More effective, would be filtering devices to clean the urban air of the mist of its contaminating particles. Suspended particles can be extracted from air by filters, spun out by cyclone devices or precipitated electrostatically, but filtering is the least expensive method.

Without an effective plan for removing dust the war against the hazard cannot be won. There must be a cleaning schedule establishing priorities, frequency and time. All spaces of the stack area should be regularly cleaned. During the cleaning drive special attention should be paid to remote corners, spaces behind cabinets and under desks, in order to remove dust and refuse harbouring insects (cockroaches, silverfish, etc.)

Among the cleaning devices vacuum cleaners are most appropriate. Compressed air guns under an exhaust hood are also considered an effective tool for removing dust. Ionized air guns, which were introduced in 1969 to aid custodians of archives and libraries in their never ending problem of dust, have also proved suitable. The compressed air guns with built-in static eliminators spray conductive air over the objects to be cleaned, in order to remove accumulated dust par-ticulates. Dusting devices such as brooms, brushes and cloths are ineffective and should be considered as being obsolete.

summaries

Accumulation of Solid Particles on Documents. The Example of the National Archives of India

Dust of various origins in the environment of tropical and subtropical regions is a common phenomenon and the Indian sub-continent is no exception. These particles adversely affect documentary cultural heritage in various ways. To find out more relevant facts a study was conducted in the National Archives of India.

The dust accumulated in the repositories of the NAI was composed of heavy and light particles, most probably of inorganic and organic origin. Its colour was black, while that found in

libraries located in small cities was brown and almost completely inorganic. The dust of metro-politan cities was sticky while that of small cities was not.

The rate of dust accumulation during the year was highly dependent on the rainfall, being highest in the dry summer and lowest during the rainy period July-September. The total dust ac-cumulated in the repositories of the NAI varied in different Stack areas from 6.07 to 7.14mg/m2 per annum. These numbers are alarming. Advice is given as to how they can be reduced.

L'accumulation de particules solides sur les documents. L'exemple des Archives Nationales de l'Inde

Les particules de poussiere d'origines diverses sont un phenomene courant dans Penvironnement des regions tropicales et subtropicales et le Subcontinent Indien ne fait pas exception ä cette regle. Ces particules ont un effet negatif sur l'heritage culturel que constituent les documents ecrits de differentes facons. Une recherche a ete menee aux Archives Nationales de l'Inde (NAI) afin de decouvrir davantage de faits pertinents.

La poussiere accumulee sur les documents deposes aux Archives Nationales de l'Indecom-porte des particules lourdes et legeres tres probablement d'origine d'une part inorganique et d'autre part organique. Elle est de couleur noire, alors que celle trouvee dans les bibliotheques si-tuees dans de plus petites villes est marron et est presque completement d'origine inorganique. La poussiere des grandes metropoles est collante, ce qui n'est pas le cas dans les petites villes.

Le degre d'accumulation de la poussiere au cours de l'annee depend tres fortement des pre-cipitations. Il atteint son niveau le plus haut pendant l'ete qui est sec et son niveau le plus bas pendant la periode des pluies de juin ä septembre. Les quantites totales de poussiere accumulee dans les depöts des Archives Nationales de l'Inde varient, selon les endroits oü sont Stockes les documents, entre 6.07 et 7.14mg/m2 par an. Ces chiffres sont alarmants. Des conseils sont don-nes sur la facon de les reduire.

Die Ansammlung von Feststoffpartikeln auf Dokumenten. Das Beispiel des Nationalarchivs von Indien

Staubpartikel verschiedener Herkunft sind eine gängige Erscheinung in der Luft von tropischen und subtropischen Regionen, und der indische Subkontinent ist hierin keine Ausnahme. Diese Substanzen können das Kulturerbe in Schriftform in verschiedener Weise schädigen. Zur Ermittlung einiger entsprechender Tatsachen wurde im Nationalarchiv von Indien eine Untersuchung durchgeführt

Der Staub in den dortigen Magazinen besteht aus schwereren und aus leichteren Partikeln, höchstwahrscheinlich teils organischen und teils anorganischen Ursprungs. Seine Farbe ist schwarz, während der Staub aus Bibliotheken in kleinen Städten braun ist und nahezu vollständig aus anorganischem Material besteht. Der Staub in städtischen Metropolen ist klebrig/ fettig, der in kleinen ist dies nicht.

Der Grad der Verschmutzung über das Jahr ist in starkem Maße von den Niederschlägen abhängig. Er ist am höchsten im trockenen Sommer und am niedrigsten während der Regenperiode Juli bis September. Die Jahresmengen sind verschieden in verschiedenen Magazinbereichen; sie