It's been more than three years since massive floods wreaked havoc in Prague. Although all the visible marks have been cleaned up and repaired in the city, the restoration work is far from finished: there are still tonnes and tonnes of paper documents from flooded archives waiting in refrigeration plants. In Czech Science today we visit one of the drying and rescue centres.
During the 2002 flood, some 200 cubic metres of documents were rescued from the archives of Prague's National Technical Museum. Just as they were, soaked in muddy water, the documents were tied up in plastic bags and rushed to refrigeration plants before the water and mould could start their work of destruction. Katerina Supova is the head of the Technical Museum's drying laboratory.
"Our centre is unique in the amount of documents we are dealing with. In other countries, it is usually small accidents, ten books or so that get soaked and have to be rescued. But here we are talking of dozens of cubic metres of documents. The scale on which we are working is unparalleled in Europe."
Paper, paper everywhere: technical drawings, plans and sketches. The Technical Museum's archive housed for example all the plans for Prague's National Theatre and the complete technical documentation of the Prague metro.
The team have fine-tuned two methods for drying small and large-format documents, using quite unsophisticated instruments, often ordinary kitchen appliances. Once taken out of the freezer, the large scrolls are put in tubs to defrost, they are cleaned with a sponge, sprayed with disinfectant and then interlaid with filter paper and unwoven fabric. When the pile - or "sandwich" as they call it here - is some 20 centimetres tall, it is weighed down and pressed.
A4-size documents are again interlaid with filter paper and unwoven fabric but between the layers ordinary newspapers are placed. The "sandwich" is put in a plastic bag and the air is sucked out from it in an ordinary vacuum packer. The vacuum-packed paper "sandwich" is left for two weeks during which the newspapers absorb much of the dampness. The procedure is repeated three times and then the sheets are left to dry naturally. And unbelievably, they look like new.
Finally all the documents are sent to special laboratories to remove all mildew spores and for expert restoration if they need it.
The Technical Museum's drying centre is one of many such establishments in the Czech Republic. With some 20 cubic metres of documents defrosted and dried every year, the 6-member team at the museum have enough work until 2013.
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