During the initial testing and excavation of the Emanuel Point ship both the numbers and types of artifacts recovered from the Emanuel Point ship were small. Preliminary cleaning, analysis, and stabilization of the first artifacts was conducted at a temporary field laboratory (kitchen) in the Pensacola Shipwreck Survey headquarters (Mitchell 1993). By the end of the season, however, enough artifacts had been recovered from the wreck to require the services of a full-time conservator, additional laboratory space, and equipment.
Courtesy of the Historic Pensacola Preservation Board, laboratory space was made available in the basement of the T.T. Wentworth, Jr. Museum in Pensacola’s historic district. Previously, this space had functioned as a dry laboratory during the excavation of a nearby British-period site and was also suitable for a wet laboratory as it was equipped with a large amount of counter space and running water.
Fig. 73. Hundreds of illustrations have been drawn of the artifacts before and after conservation in the laboratory.
Once full-scale excavations resumed in 1994, the large number of concretions and other artifacts being recovered from the field each day required the use of a second room just for storage. Between July 1994 and July 1995, these two rooms were equipped with storage vats, indispensable Tupperware containers, refrigerators, an air scribe (pneumatic air chisel) and compressor, an X-ray machine, conductivity and pH meters, titration apparatus, computer, and the thousand‑and‑one items necessary to begin the analysis and treatment of the artifacts. Equally important was the installation of drafting and photography areas to document the artifacts.
In addition to a conservator, the laboratory was staffed by graduate student interns, an illustrator, and a host of extremely interested and talented volunteers from the Pensacola Archaeological Society, Inc. and the local community. A wide variety of chemicals, equipment, and technical support were also donated by an enthusiastic business community.
Generally, all laboratory treatment procedures followed standard methods for underwater sites as outlined by Hamilton (1994) and Pearson (1987). As noted below, certain treatments and techniques were slightly modified for various artifacts due to their condition or composition.
To date, the most numerous artifact type recovered has been ceramics. Well over 90 percent of the ceramic collection consists of unglazed coarse earthenwares. Conservation treatments, therefore, have been minimal: removal of soluble salts, organic stains, and some marine growth.
The most effective treatment for removing stains (tannin and/or metallic sulfides) has been immersion in hydrogen peroxide or citric acid. Hamilton recommends immersion in 10-25% hydrogen peroxide for 24-36 hours (1994:19). In practice, however, it was found that a three percent solution was very effective in removing organic stains in a relatively short time (1-3 hours). A three percent solution of hydrogen peroxide is very inexpensive and can be obtained locally at any grocery or drug store. More stubborn stains (black metallic sulfides) and some adhering marine growths required treatment in citric acid (5 percent) for anywhere from three to forty-eight hours.
A few ceramics were found with varying amounts of iron oxide corrosion products adhering to their surfaces. These required mechanical cleaning with dental picks and soaking in five percent solutions of EDTA (ethylene diamine tetraacetic acid [di-sodium salt]) or oxalic acid. The use of oxalic acid was terminated when it proved too effective and over-cleaned one fragment of tin-glazed earthenware. Fortunately, the few glazed ceramics that were recovered appeared to be less susceptible to staining and usually only required rinsing.
A number of Spanish olive jar fragments retained traces of pine resin or pitch on their interior surfaces. If these sherds were allowed to dry the resin would spall off from the surface. Consolidation with PVA (polyvinyl acetate) or acryloid B-72 was impractical since the resin dissolved in alcohol, acetone, or toluene. Therefore, the water soluble consolidant, PVAL (polyvinyl alcohol) was added to the final rinse water. A fifteen percent solution of PVAL/distilled water effectively consolidated the resin to the sherd.
Soluble salts were removed after cleaning by placing the sherds in a series of distilled or de-ionized water baths. Rinsing continued until conductivity readings stabilized below 20µs as monitored by a conductivity meter.
Over 600 concretions have been recovered from the ship. Because of the pH, depth, and mineral contact of the seawater and seafloor, the composition of the concretions are friable and sandy in texture. Consequently, many of the smaller fastener concretions were found broken, possibly from prior storm and wave events at the site. All of the concretions, regardless of size, had to be handled with care especially during transport.
In nearly every case, the concretions have lost all of their original iron. Various corrosion processes have converted the iron to a very black iron-sulfide slush. As is commonly the case, concretion molds were formed preserving details of the original form. A pneumatic chisel was used to inscribe a line along or around the concretions. By hitting along this line with a chisel and a hammer, the concretion were broken in a predetermined manner. Oddly-shaped concretions were X-rayed and the resulting radiographs used as direction maps for cleaning. Corrosion residues were removed by simply washing them out with water and/or by dental picks and stainless steel wire. After the residue was removed, the concretion voids were filled with epoxy (Hysol 1301).
Often, wood remnants from the ship’s planking or timbers have been incorporated into the concretion. Considerable care had to be taken when cleaning the mold cavities so that the wood, which is still very soft and porous, was not removed. Without care, additional spaces in the concretion could be created and, thereby, cause casting compounds to flow into the new areas and distort the original shape of the artifact. A few concretions contained wood riddled with teredo holes. Once these specimens had been cast, and the remaining concretion removed, replica artifacts were produced surrounded by epoxy-cast teredo worm casings.
One iron shot (00,515) was recovered from the wreck. Due to its compact and spherical mass, a substantial iron core was found underneath approximately 2.5 cm of built-up concretion. After the concretion was removed the iron was successfully treated with a standard electrolysis treatment as outlined by Hamilton (1994 and 1976). Similarly, one large composite concretion composed of five fasteners was found to contain both molds and corroded iron. In this case, the molds were first filled with hysol epoxy and after the concretion was removed, the iron/epoxy artifacts were treated by electrolysis.
During stern excavations well over 200 fragments of lead sheathing or patching were recovered. Since the corrosion products of lead are stable (Hamilton 1994:102), conservation treatments have been minimal. Selected lead fragments have been cleaned by electrolysis or placed in a ten percent solution of hydrochloric acid (HCl) to reveal surface details that occasionally were obscured by a thin layer of calcium carbonate, lead sulfide and/or lead oxide. Chemical cleaning or electrolytic cleaning is non-abrasive and, in this case, permitted surface impressions of what was very likely sail cloth to be revealed.
Several lead objects, notably the bodoques (lead-covered iron shot), were found with adhering concretion. These pieces were easily freed of concretion with an air scribe, polished with baking soda, and sprayed with a protective coating of acrylic spray.
Fig. 74. Documentation and study of artifacts, such as this analysis of lead sheathing, is a routine part of laboratory work.
Only four cupreous artifacts were found: a brass ring (08,824), a copper pitcher (07,852), a copper coin (00,544), and a copper cooking cauldron. The latter was found during test excavations and was intentionally left on the site until full scale excavations could resume in what is very likely the galley area of the vessel. A small rivet from the cauldron was recovered for examination.
The brass ring, which may be associated with the ship’s rigging, required a short term cleaning in electrolysis, rinsing, and a gentle polish with baking soda. As a final stabilization step the ring was placed in a solution of one percent BTA (benzotriazole) for twenty-four hours. BTA forms an insoluble, complex compound with cupric ions and forms a barrier against any moisture that could cause future corrosion such as “bronze disease” (Hamilton 1994:92).
A copper pitcher (07,852) was found heavily corroded into copper sulfide. Due to its fragile nature, a long-term, passive treatment in a three percent sodium sesquicarbonate bath was chosen. By placing the artifact in an alkaline solution, soluble cuprous chlorides may be passively removed. This treatment is likely to last from one to two years. Because a custom made aquarium was used as a the treatment vat, it was possible to display and treat the object at the same time. The solution is periodically monitored for chloride counts and, when necessary, changed. Once it has been determined that the chloride levels are at an acceptable level (below 100 ppm) the vessel will be carefully dehydrated, treated with BTA, and consolidated.
As mentioned earlier, the copper coin also received passive conservation. Prior to treatment, it was not known whether the coin was silver, copper, or an alloy of both. In this case, an alkaline dithionite (see Pearson 1987:242 and Hamilton 1994:100) was chosen as the method most likely to preserve original details of the coin and equally suitable for either type of metal.
Bones and teeth were recovered from the wreck in very good condition except for some slight organic staining. In a few cases, bones were cleaned in 3% solution of hydrogen peroxide as outlined above for ceramics. Like the ceramics, all faunal materials were of rinsed in a series of de-ionized water baths until a conductivity reading below 20µs was achieved. Following the removal of salts, all faunal materials were dehydrated in a series of alcohol baths followed by acetone. Immediately afterwards, faunal specimens were placed in a 10 percent solution of acryloid B-72/acetone for consolidation. This treatment procedure proved very effective for the smallest rat vertebra to the largest cow ribs. Only very slight exfoliation and/or cracking was observed on some of the larger bone fragments.
The majority of the botanical remains (olive pits, nutshells, seeds, leaves, etc.) have only recently been analyzed. In consultation with paleobotantist Lee Newsom, it was decided that these specimens should be identified before any conservation treatments were applied. Therefore, all specimens were stored wet. To retard any fungal or bacterial decomposition the specimens were placed in refrigerated storage in a 20% solution of ethanol/D.I. water. Should these materials be displayed at a later time, selected specimens will be dehydrated and consolidated with a suitable resin such as PVA or acryloid B-72.
Textiles and Rope
Only one fragment of textile has been recovered from the ship. When a large lead fragment was removed from a gudgeon concretion a small piece of textile was found preserved between the outer lead covering and the corroded iron arm of the gudgeon. Undoubtedly, the infusion of iron corrosion products from the gudgeon and the close proximity of the lead allowed the piece to survive. The textile fragment has been cleaned in a weak solution of hydrochloric acid (10 percent) and placed in refrigerated storage until identification can be attempted.
Two types of rope or cordage have been recovered from the wreck: hemp and grass fiber. Both rope types were found more or less covered with an orange-colored iron-type corrosion. To more accurately measure and determine the rope’s composition it was decided to place the fragments into a 5% solution of EDTA (di-sodium salt) for cleaning. In the case of the hemp fibers the treatment proved very effective and left the rope intact with its more natural lighter color. Unfortunately, the grass fibers which turned out to have been fashioned from short sections of linear fibers quickly dissociated from their original form and separated into hundreds of short segments once the iron corrosion was removed. If fibers of this type are found during later excavations it is planned to consolidate them prior to removing any concretion, if any attempt is made to remove concretions at all.
Because the samples of insects (American cockroach wings, othecas, and egg cases, as well as hide beetle wing covers) appeared extremely fragile, the only con-servation treatment applied to them was placement of samples into 100% ethanol for storage. Study specimens were then obtained by placing selected specimens on microscope slides and sealing the insect remains between the glass slide and a cover slip with a thin solution of PVA glue.
Stone artifacts, such as the shot, required only a small amount of mechanical cleaning with an air scribe or dental pick to remove small amounts of adhering concretion or shell. A few small spots of black surface discoloration were removed by spot treating with a mild solution of HCl applied with cotton swabs.
Ballast stones recovered from the ship’s hull were generally covered with marine growth. Those ballast stones chosen for identification were slabbed so that their natural surfaces could be examined without the use of chemical treatments.
Wood and Leather
Various items of wood recovered in 1993 required more elaborate conservation techniques than were available at the Pensacola Shipwreck Survey headquarters (Mitchell 1993). These included two dunnage specimens, two tool handles, a galleon carving, a cork, and small timber recovered from the port pump well. Each of these specimens was treated by freeze-drying at the South Florida Conservation Center in Pompano Beach, Florida. Prior to freeze-drying each artifact was given a pre-treatment in PEG (polyethylene glycol, 30% PEG 300, 20% PEG 1000, and 10% PEG 400 in distilled water) for six weeks (Maseman 1994).
Similarly, all leather artifacts were treated by freeze-drying following a pre-treatment in 15% glycerol for four months (Maseman 1994). Both the PEG and glycerol pre-treatments were designed to “bulk” up the wood and leather prior to freeze drying. The methods successfully prevented subsequent cellular collapse (that could have led to extreme shrinkage and deformation).
Certain artifacts such as shell, coral, stone, and a large number of the lead fragments required essentially no treatment beyond simple washing and air drying. Approximately, 250 ml of mercury was also recovered and likewise required no special care other than carefully pouring off a small amount of seawater which had been recovered along with it. In consideration of the potential health hazards associated with mercury, the very heavy liquid was placed in a tightly sealed polyethylene bottle and placed in a secured location where it cannot be accidently dropped.
It is estimated that at least one more year will be required to finish the analysis and conservation of the remaining untreated artifacts. The majority of the this time will necessarily be spent casting nearly 400 concretions. Several of these are quite large (gudgeon arms and a pintle), and at least one is also very challenging: the breast plate (00,712). Undoubtedly, as these “excavations” continue in the laboratory many more exciting finds will be revealed.
If excavation of the ship continues at a later date some future considerations for the laboratory are necessary. A freeze drier, vacuum chamber (for consolidation and casting uses), and one or two more air scribes are required. If it is decided that the copper kettle and the anchor are to be raised it will necessary to obtain suitable vats for their treatment and storage.
|Concretions||Iron (fasteners, etc.)||12||128||471||611|
|Metal||Lead (sheathing or patching)||5||143||109||257|
|Lead (intrusive fishing weights)||3||0||0||3|
|Iron (fasteners, etc.)||15||11||3||29|
|Iron and Lead (composite shot)||0||1||2||3|
|Mercury (ca. 250 ml)||0||0||2||2|
|Wire rope (intrusive)||5||0||0||5|
|Other (slag, intrusives, etc.)||37||0||0||37|
|Plugs or stoppers||0||4||0||4|
|Peg with tenon||0||1||0||1|
|Pump well board||1||0||0||1|
|Organic||Bone (mammal, fish, rodent, etc.)||64||326||31||421|
|Teeth (pig, shark)||0||1||3||4|
|Glass||Green and amber fragments||2||0||0||2|