Bleaching Workshop

Bleaching Workshop
Gaining confidence with a powerful chemical
16 July 2012

A bleaching workshop overview was presented on 20 June by Robin Tait(NLA) and Nick Zihrul from the Australian War Memorial. The workshop was held at the NLA Preservation Lab. The workshop was attended by 14 conservators and students from the National Gallery of Australia, Australian Maritime Museum, National Australian Museum, Art and Archival, National Film and Sound Archive and students from University of Canberra. This was a overview workshop taken from the original 5 day intensive workshop presented by Renate Mesmer and Julie Biggs at the Art Gallery of NSW.

Bleaching workshop attendees

Bleaching workshop attendees

Bleaching is a conservation technique that is rarely used in Australia and most conservators have very little experience. The workshop started with the theory of bleaching followed by practical demonstrations of the different bleaching techniques. Two different techniques were shown and they were Oxidation and Reduction. Oxidation bleaching included:  Hydrogen peroxide, Potassium permanganate and Calcium Hyperchlorite.  Reduction bleaching involved using sodium borohydride. The theory of bleaching included the application methods and decisions involved when choosing a bleaching method.

Potassium Permanganate bath

Potassium Permanganate bath

Potassium permanganate was a dramatic bleaching method because of the dark purple coloured solution. This meant the items were not very visible so it was hard to observe any changes during the process.  The items also come out looking brown and only when placed in a conversion bath the item becomes almost white again and the changes are visible. It was found that potassium permanganate  and Calcium hypocholorite bleaching yielded the best results.

Some bleaching results

Some bleaching results

Towards the end of the workshop people seemed excited about bleaching methods and enthusiastic to carry out more tests on bleaching methods. This workshop has certainly given conservators more confidence and experience in bleaching techniques.