Abstract
The present work aims to develop and establish conservation processes for cleaning marine archaeological silver coins - the Shoiba Hoard Coins in Red Sea, Shoiba Port, near Jeddah, Saudi Arabia. To help the archaeologists study and date these coins, it was necessary to reveal the impeded decorations and the inscriptions on these coins. Before establishing the experimental work to evaluate the selected conservation processes, various tests were performed on different types of the selected coins to assess their statement and condition. XRD analysis was used to characterize the coins. Also scanning Electron Microscope (SEM) attached with energy-dispersive x-ray analyzer (EDX) was used to identify and analyze the corrosion products on the surface of the coins. In this study 5 cleaning methods within various conditions were tested for cleaning the current coins. The efficacy of the combined use of alkaline Rochelle salt and reduction cleaning techniques were evaluated. To evaluate the usefulness of the suggested conservation processes used in this study for cleaning the hoard coins, the coins before, during and after the cleaning processes were investigated by various techniques. SEM with EDAX and XRD techniques were used to characterize the coins after the final conservation. The results showed that the best method that can be used safely and successfully for cleaning of the studied coins is as the following a) initially the corroded coins have to be treated with alkaline Rochelle salt, b) then treated with alkaline dithionite reduction technique or electrolytic reduction technique, finally c) the coins should be rinsed, dried and followed by isolation. The conservation processes developed in this study can be used effectively, safely, and successfully for cleaning of corroded marine archaeological silver coins in this treasure and the simulated marine archaeological coins. The archaeological study of the decorations and inscriptions that appeared on the surface of the coins after their conservation confirms that these coins belong to the Rasulids (Banu Rasul) Dynasty and date back to 1229 to 1454 A.D.