Home Conservation projects The conservation and restoration of underwater archaeological finds from the Murter - Mijoka site
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The conservation and restoration of underwater archaeological finds from the Murter - Mijoka site

The results of three underwater archaeology campaigns carried out at the Murter-Mijoka site by the staff of the Croatian Conservation Institute's Department of Underwater Archaeology, is the location of over 700 finds. The majority of finds consist of small archaeological objects manufactured of brass, bronze, lead, glass, glass paste, wood and bone. This material was brought for treatment to the Croatian Conservation Institute's Department for Conservation of Underwater Archaeological Finds in Zadar.

The objects were placed in tap water pools upon delivery. This initiated the necessary process of desalinisation, lasting several months and involving regular changes of the water and instrument monitoring of the quantity of salt excreted from the objects, based on which the time when the objects were ready for further conservation treatment procedures was established. Deionised water was used in the final phase desalination baths, which accelerated the effect of cleansing the objects of salt. The completion of desalinisation was followed by photographic documentation of the condition of all objects prior to treatment, and the selection of objects on which conservation and restoration work would be conducted.

 

Lokot prije obrade Srce prije obrade Kutijica prije obrade Utezi prije obrade

Metal objects prior to treatment

Over 200 metal objects of various types were treated at the metal treatment workshop, among which we can single out: brass combination locks, clocks with gold-plated brass casings, weights of various sizes and decoration, trays from goldsmiths scales, bronze candlesticks, razors and rings. Only mechanical methods were employed in removing corrosive deposits from objects made of brass and bronze, while chemical methods were employed for lead objects in respect of the characteristics of this metal. The mechanically cleansed objects were cleaned to their original surfaces under microscopic observation using scalpels of various sizes and a dental micro motor. The chemically cleaned objects were treated using a Kompleksal III (Ethylenediaminetetraacetic acid disodium salt dihydrate) solution, after which they were neutralised by multiple boiling in tap water. After cleansing, all of the objects were actively stabilised by immersion in a 3% alcohol solution of benzotriazole, and subsequently, as the final procedure, provided with surface protection in the form of a coating of 2% Paraloid B72 solution in ethyl acetate. Glass objects were mechanically cleaned using a soft brush in alcohol. They were then rinsed in deionised water, and upon the completion of the cleaning procedure protected by a coating of a 2% Paraloid B72 solution in ethyl acetate. Over 50 glass objects or varying size and shape were processed in this fashion, and over a thousand pieces of glass paste beads of various colours, shapes and sizes.

 

Perlice prije obrade Staklo prije obrade Sat prije obrade Drvo prije obrade

Glass and organic objects prior to treatment

Objects of bone (combs, sundials and knife handles) and of wood (the handles of razors and knives) were conserved at the organic material treatment workshop.
The bone objects were cleaned mechanically using scalpels of various sizes, soft brushes and alcohol. They were then lacquer-coated (2% Paraloid B72 solution in ethyl acetate). Wooden razor and knife handles were first mechanically cleansed of calcareous growth, and then prepared for impregnation using the PEG method. This method replaces the water in the structure of the wood with polyethylene resin. Wooden objects are placed in a water bath into which a fungicidal disinfectant, i.e. a 2% solution of borax and boric acid, is added. A previously calculated quantity of polyethylene glycol is added on a daily basis until a concentration of about 95% in the solution is achieved, accompanied by the gradual increase of the solution's temperature to a final value of 60oC. Following the completion of the impregnation process, which lasts a month, the objects are extracted from the bath and gradually dried with the removal of excess polyethylene glycol, after which they are protected by a coat of 2% Paraloid B72 solution in ethyl acetate.
As a result of the large number of finds from this site, a number of objects have not yet been processed and conservation and restoration work on them continues.

 

Lokot poslije obrade Srce poslije obrade Kutijica poslije obrade Utezi poslije obrade

The objects after conservation treatment

Perlice poslije obrade

Staklo poslije obrade Sat poslije obrade Drvo poslije obrade

 

Anita Jelić