Conserving Pewter Spoons from the Atocha - by Capt. Gary Randolph

While diving on board the salvage vessel J.B. Magruder, diver Tom Shields recovered what we thought at the time to be three silver spoons from the Atocha site. These spoons where 100% intact and in beautiful condition, having very little encrustation due to the fact they where found in very hard, consolidated mud. Once on board the recovery vessel they where individually tagged, logged into the ships archaeological log and stored in fresh water for transportation to our conservation laboratory. Upon reaching the lab, we had a chance to take a closer look at these fantastic artifacts and discovered they where not made of silver.

These spoons where pewter! This made them an even more rare find since never before, in all previous salvage work done on the Atocha site had spoons like these been found. The spoons are topped with a crudely cast, seated lion knops. Knopped spoons were very common for this period. Many had other characters such as balls, acorns, apostles, hooves and maidenheads. Pewter and other metal spoons began to replace wooden spoons as the common form of tableware in the late 1500's. We started the conservation process by removing the light calcareous concretion with an acid bath of 10% muriatic acid / 90% tap water. This only took a few minutes to complete the process, then they were rinsed in tap water to thoroughly remove any acid. From this point they will go into the electrolysis treatment. We start by wrapping the spoons in foam padding with rubber bands to hold it all together. This will help stabilize the surface of the spoon and help the pewter that has started to deteriorate become stable again. This procedure helps in saving the detail on the surface that would otherwise be lost in the electrolysis process.

We decided to use a process called anodic stripping and cathodic polishing to conserve these spoons. We began with the polishing process (this is the standard electrolytic reduction procedure). In this process the artifact becomes the "-" or the cathode and the stainless steel sheet in our tank becomes the "+" or the anode. This will loosen the resistant black film on the surface. After one hour of treatment in a 10% sulfuric acid / 90% tap water solution, we removed the spoons from the tank and switched to the stripping process. We replaced the stainless steel sheet with a lead sheet, switched the wires so the lead becomes the "-" cathode and the spoons become the "+" anode. We removed the foam wrap, lightly brushed them with a stiff bristle brush and started the stripping process by returning them to the tank with the new setup for one hour.

This process had to be repeated 5 times or until at the end of the polishing stage, the artifact appears bright and the surface clean of all black deposits. A final rinse in distilled water, 2 hour bath in EDTA and a very light polishing with baking soda & clean towel will complete the conservation process. We handled the spoons with gloves to protect it from oils on our hands. The artifact can be sealed with Krylon clear coat spray to protect it from handling damage or stored as is in a plastic zip-lock bag. We chose to store it in a plastic bag for now. We will be posting more conservation information on this site, so stay tuned!