Conservation-Restoration Work on Small Finds from the Premuda Site – the Post Medieval Szent Istvan Shipwreck
The underwater Premuda site is the location of the remains of the sunken Austro-Hungarian ship Szent Istvan. A part of the ship's equipment was extracted from the sea during an archaeological survey of the site and delivered to the workshop for conservation-restoration treatment.
Once they had been recorded and photographed, the condition of the artefacts as found was documented. The metal artefacts were partially fragmented and their surfaces were to a large extent covered with various corrosion products, encrusted mollusc shells and calcification, lime and organic deposits, but are in a good state of conservation. The artefacts of organic origin are relatively well preserved and, to a lesser extent, damaged by the activity of marine organisms.
Following the photographing and documentation of the artefacts as found, they were subjected to preliminary cleaning of easily removed deposits using brushes under running water and then isolated in polypropylene nets and placed in a desalination bath. The desalination process was conducted until the concentration of chloride, determined by potentiometric titration, was reduced to a minimum. Once desalination was completed the artefacts were removed from the water and left to dry out in the air. Drying was followed by further conservation-restoration treatment of the artefacts. The boot, made of organic materials, was subjected to a combination of mechanical and chemical cleaning. The upper section of the boot was cleaned by submersion in ethanol and brushing with brushes of varying profiles and hardness. The encrusted mollusc shells and lime deposits were removed from the lower section (sole) of the boot by the mechanical use of scalpels of various sizes. After cleaning the boot was consolidated by submersion in a 5% aqueous solution of acrylic consolidant.
The cartridge case and nozzle, made of a copper alloy, were cleaned mechanically with scalpels of various sizes, ultrasonic chisels, milling burrs mounted on flexible micro motor shafts and micro abrasive blasting (using glass beads ranging from 50 to 110 ?m) to remove corrosion products and other deposits from the artefacts. The mechanical cleaning was conducted in a controlled and careful manner under 5-20x magnification up to the level of the original surface. When the original surface of the artefacts had been revealed they were polished with the aid of soft rotary brushes. A mixture of reversible Paraloid B72 polymer and Cosmoloid H80 microcrystalline wax in toluene was applied as a final protective coating of the copper alloy cartridge case and nozzle.
The rangefinder is made of a combination of copper alloy, glass, leather and rubber – mechanical and chemical methods were used in its cleaning. The parts of the rangefinder made of rubber and leather were cleaned with ethanol and brushing with soft brushes and consolidated in a 5% aqueous solution of acrylic consolidant. The glass fragments of the rangefinder were cleaned by brushing with soft brushes, mild soap and alcohol. They were then rinsed in distilled water and, once the cleaning procedure had been completed, protected with a coating of 2% solution of Paraloid B72 in acetone. Coarse corrosion and lime deposits were first removed from the rangefinder with the aid of scalpels and a micro motor. Gradual cleaning and removal of deposits from the rangefinder revealed marks on its surface, a measurement scale, inscriptions and numerous details that can assist us in determining the authenticity of the artefact.
Further careful work under microscopic magnification (5-20x) using micro abrasive blasting and ultrasonic chisels removed the remaining stubborn deposits and corrosion products that could not be removed with a scalpel. The revealed original surface of the rangefinder was then polished and protected with a coating of a solution of 2% Paraloid B72 and 5% Cosmoloid H80 in toluene. Upon completion of the work the artefacts were photographed and technical documentation was drawn up detailing the work conducted on each artefact.