Mauro Alvarez (front) and Roger Dooley (back) in lab preparing treatment solutions.

 CONSERVATION REPORT

For the past ten days of my stay in Rota, the undersigned  performed various activities to continue the conservation treatment of the valuable archaeological collections from the wreck site of the Santa Margarita galleon. The following are the work done on the materials:  

Porcelain and stoneware sherds previously cleaned during November 2000 were allowed to dry, except for the few, which were found to be with concretions. Those sherds were immersed in a 5% by volume solution of hydrochloric acid and water.  After an overnight immersion in acid, the pieces were taken out and soaked in water to wash off acid residue that might have penetrated the pieces. Then, they were rinsed in a series of water baths for further desalination.

After long immersion in water, the beads were subjected to a salt test, which yielded negative result. They were then allowed to dry.

These objects are made of igneous rocks.  They have been soaking in freshwater since November 2000. The water was tested for salt content and was found to be positive.  The water was changed and after an overnight soaking, tests yielded a negative result. The weights were allowed to dry and coated with a solution by weight of 5%PVA in xylene. During the treatment one of them came apart.   It was then readily joined together using PVA Emulsion.

These objects were found to be dried and did not undergo complete desalination.   Some of them had concretions in between cracks. Prior to immersion in water, these objects were exposed to a moist environment by placing on a petri dish floating in water in an airtight container. When the stones moistened, immersion in water followed. After an overnight soaking, they were transferred to a solution of 3% by weight of tetra sodium salt of EDTA for cleaning. The next step was to immerse them in water to remove the acid residue and to start with the desalination process. Water was changed daily. Each time water was changed salt test was performed. When water yielded negative to salt content, the stones were then allowed to dry.

 Copper Alloys

Materials of this type excavated in 1999, have not undergone cleaning during the November 2000 trip due to time constraint and the amount of work to be undertaken. However, all of these materials were immersed in a solution of 2.5 % by volume of Sodium sesquicarbonate.

For this trip, parts of the materials were taken out from the storage solution and were subjected to cleaning. These objects were first mechanically cleaned, followed by immersion in a solution of 3% by volume of hydrochloric acid in tap water. After the cleaning process, they were soaked in water to remove the acid residue. Then, they were moved to a solution of 2.5% by volume of Sodium sesquicarbonate for further desalination. A total of 365 pieces were cleaned.

Medal

During this field season of excavation another copper alloy medal was found. As previously done to this kind of object, it was first degreased with acetone and then immersed in a solution of 3% by weight of citric acid and 1% by weight of thiourea in water. After an overnight immersion, it was brushed under running water. Then it was soaked in a solution of 5% by volume of acetic acid. The object remained in the solution for 8 hours then was washed. The process was repeatedly using the acetic acid solution until a recognizable image came out.

Iron

The majority of the materials of this type have not been subjected to further conservation treatment during this trip because they are already immersed in a solution of 5% by weight of sodium hydroxide in water for desalination.  Those items covered with heavy concretions have not been in the solution for quite sometime, so we start immersing them in a solution of 5% by volume of hydrochloric acid in water to remove the thick calcareous incrustations.   The next step was mechanical cleaning.  A total of 16 iron objects have undergone this process.

Since September 2000, the ropes (2 pieces) have been in a solution of PEG400-Ethanol-Water mixture, it was decided to put them on an air drying process at room temperature.  As soon as it became hard, they were applied with a solution of 50% by weight of PEG 4000 in water, to seal off the pores and prevent humidity from affecting the objects.   Other small items of this kind including caulking materials and seeds were immersed in a solution of PEG 400-Ethanol-Water mixture to initiate the consolidation process.

These artifacts are small in size. After months of immersion in water with Dowicide A, a sample of water was taken from each of the containers to perform a salt test. The results indicated salt was still present, so water was changed constantly for three (3) days.  Each time water was changed; tests were conducted until final tests yielded negative results. The objects were then immersed in methanol. The alcohol was allowed to evaporate. When there was no more alcohol in each of the containers, objects were coated with a solution of 5% by weight of PVA in xylene.

SALT TEST RESULTS

These two (2) sets of material found in the wreck site have been immersed in water since September 2000. Water was changed constantly. During this trip, when chemicals and equipment for the analysis of salt content became available, samples of water from these objects were analyzed. Once salt tests yielded a negative result a dewatering process was started.  A table was prepared to prevent any drastic change on the structural composition of the ivories due to the removal of water.

 TABLE USED FOR THE DEWATERING PROCESS

After the dewatering process, the objects were immersed in a solution of 3% by weight of PVA resin in methanol at least for six months.

These type of materials especially those that are bigger in size have been immersed since November 2000 in a solution of 5% by weight of PEG 4000 in water. Only those items, which were small in size, were immersed in water with Dowicide A.  During this trip, they were taken out of the water and immersed in a solution of 5% by weight of PEG 4000 in water.

This season, a large piece of wood was found, so we began to process it including taking a sample for wood identification. The rest of the wood part was immersed in a solution of 5% by weight of PEG 4000.

RECOMMENDATIONS

 1.  Even if we have finished the treatment of the considerable amount of artifacts, we are still in a process of desalination and consolidation of artifacts from the 96/99 seasons. Therefore, it is recommended that periodic monitoring of those artifacts must be undertaken such as checking to see if there are any leaking in the containers, checking to see if solutions are drying up and any occurrence of deterioration.

 2.  For the tryptichs, it is recommended that the solution level inside the container should be monitored and maintained. Once the level of the solution goes below the mark, methanol should be added.

 3.  Continuation of the conservation treatment for each type of materials should be undertaken in the future.



Prepared by:
MAURO T. ALVAREZ
Conservator
Archaeological Objects

Since 27 Jul 2001