The early 20th century porthole
In 2017, the early 20th century porthole was donated to the Maritime Museum Sergej Mašera Piran. It was in extremely poor condition, as it had not been desalinated when lifted from the sea, and had been degrading for more than a decade due to the harmful effects of salts and air humidity.
The porthole’s surface was covered with various corrosion products, seashell encrustations and other sediments. Wrought iron components were in the worst condition; brittle, fragile and heavily corroded, there were essentially no traces of iron core present.
The copper alloy parts were in better condition, however active green corrosion together with brown patina were present.
The rubber seal was cracked, the glass fractured and the metal corrosion products had penetrated into the fractures over the years.
We began intervention by removing smaller encrustations and cleaning corrosion products in order to hasten the desalination process. Desalination was carried out gradually, switching from tap to distilled water whilst measuring the conductivity at every water change in order to determine salt concentration. We kept changing the water until a stable, low concentration of salts was attained.
After drying, we continued with the mechanical removal of the corrosion products and encrustations using small tools, an ultrasonic hammer and a micromotor. Cleaning was done with utmost care and under magnification, in order not to damage the original surface. Extra care was taken when cleaning the rubber seal with a solvent at a low solution.
The surfaces were protected by applying metal conservation coatings that can be easily removed to enable local treatments if necessary in future.
In order to ensure the future preservation of the artefact it is of the utmost importance that the artefact be stored in dry conditions. When there is no possibility to control the overall museum environment a solution adopted is to place metal artefacts in air-sealed containers with special substances that absorb moisture and thus protect the artefacts.
The objects must be handled with care using exclusively gloves so as not to leave greasy or acidic residues. Fingerprints leave behind (in)visible traces which lead to faster dust accumulation.
Conservation – restoration: Ajda Purger, Igor Ravbar
.JPG)
.JPG)
.jpg)
.JPG)
.JPG)
.JPG)
.JPG)
.JPG)
.JPG)