By Chie Yoshii
The ceramics department is working on 12 marble elements, a glass panel and an enamel dial.
The marble elements are assembled with metal elements, thus it is essential for us to keep in contact with metal department regularly.
First, the condition of the marble elements was examined. Various inscribed marks likely to make assembling easier were found on the surface.
After a detailed examination, we started cleaning the surface of the marble. The white marble in particular was heavily and widely stained, and the surface dirt was remarkable.
A wax coating to protect the porous body of the marble remained on the surface of the marble, so while cleaning we needed to be careful not to remove the coating.
First, surface dust was removed using brushes and a museum vacuum. We then carried out wet cleaning; however, strong solvents were not used to avoid any risk of removing the wax coating. We used water, Synperonic A7 (non-ionic detergent diluted 1:20 in water) and diluted Biotex (enzyme washing powder) in water using cotton wool swabs.
According to some tests, a Biotex concentration greater than 0.05% risked removing the wax coating, so we used only a very weak solution.
Laponite(R) poultice (synthetic clay colloid with water) was also tested, yet because it was not so effective we did not use it.
For an aesthetic reason to match the cleaning level with the metal components, noticeable dirt on some edges of the pyramidical element was removed by steam cleaning.
Unfortunately, most of the deep stains that would have been made over time could not be removed.
As to the glass panel, it was accidently broken when the clock case was transferred and it will be replaced with a new one. However the shards were here, so we have tried to bond them. Although the surface was very dirty, the condition of the glass was quite good, so a cleaning solution of deionized water, IMS and Synperonic A7 was applied to the surface. Then the glass panel regained its transparency. We are going to bond the shards soon!
The enamel dial is also an object we are working on. There are three areas of loss need to be filled. We are going to use an epoxy resin to fill the areas and the numerals should be retouched.