- 1619 (AH 1029)
- Minted in: Agra
- (Asia,South Asia,India,Uttar Pradesh,Agra)
- Weight: 11.34 grammes
7 June 2010
Light clean to remove tarnish. Apply lacquer as surface coating.
Coin in stable condition. It was noticed that a dull grey 'cloudy' tarnish had developed on the surface of the silver whilst on display. The corrosion / tarnish product was analysed in Scientific Research (Awaiting full report). No clear reason as to why the tarnish had developed was found. Whilst it was unlikely that case materials had casued this to occur, as no other silver in the gallery appeared to have been effected in the same wayt, they can not be ruled out completly. Other possibilities such as air born pollutants carried by air flow within Gallery 34 were also considered.
Placed in ultrasonic tank, in 50:50 de-ionised water : Industrial methylated spirits ('IMS' - ethanol,methanol), for 30 seconds to remove any particulate dirt. Surface swabbed with IMS. Tarnish reduced with soft brushes and swabs moistened in White Spirit (composition variable - petroleum distillate) then rolled in wadding from 'Silvo silver and chrome' (cotton wadding,white spirit,Newburgh chalk,china clay) and applied to the surface. Fatty residue / tarnish products removed with aplications of clean White Spirit then Acetone (propan-1-one/dimethyl ketone). Three coats of 4% Paraloid B72 (ethyl methacrylate copolymer) in 50:50 IMS : Acetone applied to surface with soft brush. three coats of lacquer applied due to potential possibility of tarnish recurring.
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Object reference number: COC20231
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