Shown here is a white tray containing a document submerged in de-ionised water. It's a small 19th century print undergoing a washing treatment in the Conservation Studio at Kent Archives, Maidstone. Originally neutral, the de-ionised water has had its pH increased with the addition of an alkaline (in this instance, calcium hydroxide) which will help to flush out and neutralise any soluble acidic compounds within the sheet. Such aqueous treatments also reform the hydrogen bonds in the cellulose structure of paper – improving the sheet’s strength and flexibility – and deposit an alkaline reserve which, following the treatment, will remain in the sheet and help to neutralise any future acidity. Conservators also use de-ionised water in vapour form to reduce creases and distortion – a treatment known as humidification – and to hydrate archival-grade adhesives (wheat starch paste, methylcellulose etc.) which are purchased in powdered form and prepared by hand when required.
D is for… #DeionisedWater
Water stripped of metallic and mineral impurities provides conservators with a neutral base which can be conditioned to suit a treatment. For example, an alkaline might be added to deacidify and buffer a document through washing.
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