Journal of PaperConservation Vol. 12 (2011), No. 1 Washing, i.e. applying aqueous treatment to paper objects (usually without the use of surfactants or other additives), has a firm place in paper conservation and is performed regularly in a lot of conservation studios. Since washing is intended to remove water-soluble components, washing of paper objects containing water-sensitive media presents a challenge for paper conservators. Some objects may contain media that dissolve immediately upon contact with water or change their morpho- logical characteristics (Fig 1). Others may contain a binder which becomes water-soluble after prolonged contact with water, or when agitated, but is otherwise quite stable. Paper that is severely degraded, has a lot of tears, or is very thin can also be regarded as water-sensitive, because it is vulnerable to mechan- ical stress and would suffer from the movement of the water when subjected to immersion washing. Therefore, in this article the term ‘water-sensitive objects’ is used for objects that can tol- erate a limited amount of water, whether because of their media or physical condition. Objects that are at an immediate risk of bleeding are not suitable for the aqueous treatments discussed here. There are several washing methods designed to minimize damage during aqueous treatment of water-sensitive objects. While ‘blotter washing’ is widely applied [1], another technique is recommended in the literature—treatment using the ‘capil- lary unit’ (Fig 2). Until now, comparisons have been made be- tween blotter washing and several other washing techniques like immersion washing, and between the capillary unit treatment and immersion washing, but not between the two methods themselves. The question remained how effective the methods are in comparison and which of the methods should be prefer- red, if any. 11 Hilde Schalkx, Piet Iedema, Birgit Reissland, Bas van Velzen Aqueous Treatment of Water-Sensitive Paper Objects Capillary Unit, Blotter Wash or Paraprint Wash?* Blotter washing and washing with the capillary unit are both methods used for aqueous treatment of water-sensitive paper ob- jects. The challenge of this treatment is to remove water-soluble products while keeping the water-sensitive medium in its place. In this article the two methods are compared, along with a third method referred to as Paraprint washing. This is a washing treat- ment similar to blotter washing, but using Paraprint OL 60, the viscose non-woven fabric recommended in the literature for use with the capillary unit, instead of blotting paper. Preliminary experiments were carried out to clarify the principles behind the capillary unit treatment, and the method was adjusted to use a level surface instead of the slight slope recommended in the liter- ature. The comparison between the different methods was made by washing samples of new, unaged papers, that had been colour- ed by immersion in a highly water-soluble red food colouring dye (Ponceau 4R) to simulate the water-soluble compounds like dis- colouration and acids that washing is usually meant to remove. After treatment the samples were compared visually. Both capil- lary unit treatment and Paraprint washing gave better results than the more traditional blotter wash. The capillary unit worked well with papers that wet easily. For papers that did not, Paraprint washing was better suited as it washed out the colour more effec- tively and evenly. Finally, originals were successfully treated applying the results of this study. Kapillarreinigung, Blotter-Wash oder Paraprint-Wash? Wässrige Behandlung von wasserempfindlichen Objekten Das „Blotter-Washing“ und die „Behandlung mit der Kapillar- einheit“ sind beides wässrige Methoden zur Behandlung wasser- empfindlicher Objekte. Die Herausforderung besteht darin, wasser- lösliche Produkte zu entfernen, dabei jedoch die wasseremp- findliche Bildschicht auf dem Träger zu erhalten. In diesem Ar- tikel werden diese beiden Methoden sowie eine Abwandlung des Blotter-Washings, das „Paraprint-Washing“, verglichen. Hierzu wurden neue, ungealterte Papiere wässrig behandelt. Um den Transport unsichtbarer wasserlöslicher Verunreinigungen (Ver- färbungen, Säuren) sichtbar zu machen, waren diese Papiere zuvor mit einem wasserlöslichen, roten Lebensmittelfarbstoff (Ponceau 4R) durch Tauchen gefärbt worden. Nach der Behand- lung wurden die Proben visuell verglichen. Die Kapillareinheit und das Paraprint-Washing erzielten bessere Ergebnisse als das eher traditionelle Blotter-Washing. Eine Behandlung mit der Ka- pillareinheit ist effektiver für Papiere, die Wasser gut aufnehmen. Für schlecht benetzbare Papiere ist das Paraprint-Washing ge- eigneter, die Farbe wurde besser und gleichmäßiger entfernt. Schließlich wurden Originale unter Berücksichtigung der Ergeb- nisse dieser Studie erfolgreich behandelt. Die Verwendung der Ka- pillareinheit konnte durch einleitende Experimente wesentlich vereinfacht werden: ein geneigter Winkel ist nicht notwendig. 1 Water-sensitive media: a sample of paper with blue gouache paint during immersion washing. The loss of pigments is clearly visible.