The Runde Find: Cleaning

After 250 years at the bottom of the sea, the coins were covered with lime and stuck together in lumps. In order to identify the coins, they were separated from one another by dissolving the lime in formic acid. 

For many coins, this treatment sufficed to allow the identification of coin-type. 

In general, the gold coins were very well preserved. Removal of the lime and a thin layer of rust revealed coins that were, so to speak, freshly struck. 

  The silver coins, however, were severely corroded. Those least affected were at the centre of the clumps, surrounded by other coins, sand and lime. In some cases an entire coin had disappeared.

Cleaning was limited to what was necessary for identifying the type of coin. 

  A total of 57 000 coins were examined; 6624 were gold, the rest were silver. More than 400 different types of coins were identified, 15 of which were unknown until this discovery.

  Read more about this find at: 
the Akerendam, the Shipwreck, Salvage 1725, Salvage 1972, Overview