Konservierung von Artefakten (artifact preservation)

Hier ein interessanter Bericht von Capt. Dan Berg (Autor zahlreicher Wrack-Tauchbücher) über die Möglichkeit Artefakte zu konservieren.

Here an interesting article from Capt. Dan Berg (author of several interesting wreck diving books) about preservation of artifacts.

Capt. Dan Berg’s Wreck Valley Collection

By Capt. Dan Berg

Preservation of artifacts is extremely important and requires not only time but often a little elbow grease as well. The process usually starts on the boat immediately after an artifact is found. The first and cardinal rule is to keep the artifact wet and not exposed to air until the preservation process can begin. This is extremely important with steel artifacts which start to rust immediately upon contact with air. Soaking in fresh water is best, but salt water will do fine temporarily. Even wrapping the item in plastic will usually keep in enough moisture until preservation can begin. I have listed below some cleaning and preservation methods for different materials. Some of these methods are nonscientific and have been learned through my own as well as others experiences. Please use the information below at your own discretion.

BRASS and BRONZE shipwreck artifacts
Both brass and bronze hold up very well in salt water. Although no preservation is needed, most brass or bronze artifacts usually need to be cleaned to some degree. Any encrustation can often be chipped off with wooden picks. Wood is used so the surface won’t get scratched or marred. The first step is to soak the artifact in fresh water for about one month. This will usually leach out any chlorides and prevent the object from later turning green. To actually clean the object, several methods can be used. The first is to sand blast it or use glass beads to leave a clean dull finish. Then use a fine brass wire wheel on an electric drill or bench motor to polish.

Another method used to clean brass and bronze is electrolysis. An electrolysis bath is set up by immersing the artifact in an electrolyte solution, usually a 5% to 10%solution of caustic soda also known as sodium hydroxide or lye, and water and passing an electrical charge through the artifact. Rubber gloves, safety glasses and a rubberized apron should always be used when working with lye. To set up an electrolysis tank, start with a plastic container of a suitable size so that the artifact may be completely submerged, a car battery charger and an anode of stainless steel which has been attached to the positive side of a DC power source. Now connect the negative wire to the artifact and place it in the still empty tank. The anode should not be in contact with the artifact. The electrical current should be on before immersion of the artifact. It does not take much electricity to clean a brass artifact. For example, three amps is more than sufficient to clean a porthole. Of course, the voltage must be sufficient to achieve proper flow.  The time period depends on the size, shape, and electrical current, but since this is cleaning and not preservation, it should not take more than a day.

Finally, an acid bath can be used. Use a 50/50 solution of muriatic acid and water. Let the artifact soak, fully submerged, for a couple of days or until the artifact is clean. You will need to soak the brass or bronze in fresh water for a full month, changing the water every few days to leach out all of the acid. This soaking insures that your artifact will not turn green. A final polishing with a fine brass wire wheel or even by hand with a brillo pad will make the brass shine. As a final stage to any of the above listed methods, I suggest coating the polished brass with a clear poly-urethane spray, which helps to prevent the shine from dulling.
Brass Polishing Service

CERAMICS artifacts
Pottery , porcelain and china are all included in this category. The first rule is to immediately soak any item found in salt water in fresh water. Soak the item for approximately eight weeks, changing the water every day or so. I prefer to use warm water rinses followed by cold water baths during every change of water. The idea is to leach out as much salt as possible from the artifact. Steve Bielenda uses the toilet bowl tank as his artifact bath. His idea is logical because items placed in the tank are constantly being rinsed with fresh water each time the toilet is flushed. Hank Garvin recommends soaking china artifacts in a lemon juice bath. The mild acid in the lemon juice helps to leach out salt and should not harm any ornamental gold leaf on the china.

After the initial soaking, use a warm water rinse with a mild soap solution. If calcium deposits are present, use a vinegar bath, but be careful; some decorative patterns, especially gold leaf, are very delicate. Soak in fresh water after the vinegar or lemon bath.

After the final rinsing, if the artifact still has its original glaze, this is all the preservation that is needed. If the object is porous, it is advisable to coat it with an acrylic plastic.

GLASS artifacts
Fortunately glass holds up fairly well underwater, even after decades of submersion. Usually bottles dating from the early 1800’s to the present, found on or near shipwrecks, are in good condition. There are, of course, exceptions to every rule, and I have read reports of glass dating to the early 1700’s that would crack after drying out. When intact bottles are found buried in silt or sand, they can be as clear as the day they were lost. However, if the wreck is in a strong current area or in a location where a lot of surge is present, the bottles can be dulled by the sand blasting effect of constantly tumbling around.

In order to clean glass, all that is needed is fresh water, some powdered dish washing detergent and a little elbow grease. If stubborn stains are present, a 50% solution of muriatic acid and water can be used. Remember to wear plastic gloves and to rinse the artifact with fresh water after using acid. For bottles that are stained on the inside, use a bottle brush with a mud-like solution of detergent and water. If you don’t have a bottle brush, just shake the sloppy mixture around. It will have enough abrasiveness to remove most stains without damaging the glass.

Photos: Capt. Ed Slater with a black glass bottle. Bottles inside the San Diego and Capt. Dan’s shipwreck bottle collection.

GOLD shipwreck artifacts

Photo’s Shipwreck gold. Right Teddy Tuckers treasure cross from the San Pedro Shipwreck

Gold is amazing, and, depending on the quality, it is usually found as clean and shiny as new. Aaron Hirsh, a friend of mine, told me that the best method to preserve gold after recovery is to put it in a safe. Actually, he is right; very little is necessary to preserve this precious metal, and usually cleaning is all that is required. Sometimes gold may be found tarnished. Soaking in a 10% solution of nitric acid and water will usually remove any tarnish. I have found 10 karat gold that looked almost gray and very much like dull silver, but after a little polishing with a dremel held cotton buffing wheel, jewelers ruse, and some metal polish the gold gleamed. Gold can also be tested fairly easily and accurately with a karat testing chemical kit. This comes in real handy when trying to have an item appraised. The kit comes with a fine stone and a chemical solution for each karat rating. Simply rub a small amount of gold onto the stone and start out by dropping a drop of the mildest acid on to it. If it doesn’t dissolve, go to the next stronger chemical and continue until the small scratch of gold dissolves. Each bottle is marked, so whichever was strong enough to dissolve the gold residue on the stone is the karat rating of the gold.

LEAD and TIN shipwreck artifacts
Objects of lead and tin usually survive quite well while underwater. No preservation is usually needed, but any deposits of calcium or rust crustation can be removed by hand or with a pick. The white coating is usually lead oxide. This can be removed with a 10% solution of acetic acid or white vinegar. Be careful when soaking in acid or vinegar, if left for extended periods of time, damage will occur. After an acid bath, soak in warm water followed by cool water. Repeat the fresh water baths a few times to help remove any remaining acid. Dry after immersion in a rubbing alcohol bath, allow to dry, then coat with clear plastic spray or coat with paraffin wax.

As with all organic material, leather should be soaked in fresh water for at least two weeks; then it can be carefully brushed clean with a soft nylon brush. The next step is to soak the artifact for two hours in a 50% solution of alcohol and fresh water. Next use a 100% alcohol bath. After the object is completely cleaned soak it in polyethylene glycol for approximately one month.


Silver holds up fairly well underwater, but most items such as coins will be covered in a heavy black rust like coating. In fact, to the untrained eye, silver coins usually look like junk until they are restored. First, remove as much of the silver sulfide coating as possible; this can usually be picked off. Depending on the item you can use a vinegar bath, electrolysis, or a chemical bath followed by a cleaning with tooth paste and polishing with silver polish. A dremel grinder with a fine wire wheel may even be used on some objects, then a cotton wheel and a fine jeweler’s ruse compound. Be careful if you choose the dremel grinder, as the wire wheel will scratch into the artifact’s surface. Charles Garrett offers a simple electrolysis method for cleaning coins in his book, TREASURE RECOVERY FROM SAND & SEA. His method uses an electrolyte solution of one teaspoon of citric acid and a half teaspoon of salt dissolved in one cup of water.The positive side of a three to six volt power supply is attached to a stainless steel anode on one side of the glass, and an alligator clip is used to attach the negative side to the coin which is placed on the other side of the glass. The current that flows through the solution will loosen any encrustation.

Photo: Treasure Hunter Carl Fismer with Silver coins salvaged from a Bahamas Shipwreck.

Steel and iron are the most difficult to preserve. Severe corrosion is usually the problem. The first step is to remove any loose rust or calcareous encrustation. This can be done by scraping, sandblasting or tapping lightly with a hammer. After the object is cleaned, the metal has to be preserved. Electrochemical or an electrolysis bath can be used, or, if the item is too large to be submerged in a bath, the diver can simply heavily paint the artifact to seal the object from the elements. This method does not prevent corrosion from within but is used frequently on large anchors which would be hard to soak. For an electrochemical bath, smaller items can be soaked in a 10% solution of sodium hydroxide and 90%water. Note that the solution should be kept in a sealed plastic container, and plastic gloves should always be used. Soak the item for two to six months, depending on its size. Some then choose to dry the artifact completely and coat it with polyurethane or paint. Drying of small artifacts can be done in an oven, 200 degrees for 12-24 hours. Larger items can be heated with a torch. Another sealing method would be to place it in a bath of the same solution and surround the object with zinc plates or zinc chips. The solution will bubble for about two weeks. When the artifact is removed and rinsed off, it will  have a white coating which can be left on or removed with a 5% solution of sulfuric acid. The next step is to soak it in running fresh water for approximately two days.  Dry the item completely and coat the exterior with polyurethane, paraffin wax or paint. The exterior coating seals the iron from contact with air and moisture and prevents future corrosion.

An electrolysis bath can be set up as described in the brass and bronze section of this book. Remember that the electrolysis used for brass is for cleaning and when used on steel is for preservation. The duration will vary from several days to several weeks depending on the size and age of the object. According to THE UNDERWATER DIG by Robert Marx, the current, „should be five amperes for every 25 square inches of the objects surface“. The artifact should be removed from the bath while the power is still on. The artifact should then be emerged in afresh water bath and brushed clean. The water should be changed regularly for about two weeks. Drying and sealing is identical to the electrochemical method listed above.

Another method which I have used quite successfully with dead eye straps and steel cable is to clean and dry the steel then heavily coat the strap or cable with Naval Jelly. Their are two types of naval Jelly. You want the type that paints on white then dries to a hard black finish. After several coats you basically seal the artifact preventing any air from getting to and rusting the item. I have several pieces which have been preserved in the manner and have lasted nicely for over twenty years.

Unglazed Pottery is more porous than china or glass and when found in salt water, you have to realize that this pottery allows more salt to saturate it than glazed china does. Once brought up from depth, the salt inside an artifact that is not preserved correctly will dry, crystallize and cause cracking and possible destruction to the artifact.

The first rule is to prevent the artifact from drying out. The best immediate choice is a freshwater bath, but if you’re on a boat and fresh water is not available, saltwater will due. For the car ride home, wrap the objects in plastic to keep in any moisture and prevent crystallization. Again as with ceramics, the first step to preservation is to leach out as much salt and chlorides as possible. For small objects, the holding tank of a toilet bowl works fine; other wise, soak in fresh water for approximately eight weeks, changing the water every couple of days. The next step is to soak the item in a bath of rubbing alcohol for three to four hours. Afterwards, let the artifact dry completely, which may take a few days. Drying can be assisted with an alcohol bath. Then it is advised to coat the artifact with a clear polyurethane spray or as Carl Fismer,a noted treasure hunter, recommends paint with a mixture of Elmers glue and water.

Wood is difficult and time consuming to preserve. However, artifacts like rifle stocks, cargo crates with ink writing and dead eyes tempt the novice and even the experienced wreck diver to try. The problem is that when a wood item that has been submerged for years or even decades is dried out, it will shrink and crack. According to THE UNDERWATER DIG by Robert Marx, „When waterlogged wood is allowed to dry out, the evaporation of water from its degenerated inner cellulose and lignin cells will cause the remaining outer cell walls to collapse from surface tension“. We have to preserve each wood artifact by removing all water and salt from the inner cell structure while strengthening the wood’s cell structure.

Start off by keeping the object immersed in fresh water. Alternate warm and cool water. This rinse stage can go on for weeks or months, depending on the size, thickness and particular type of wood. The best scientific preservation method is impregnation with a 60% solution of Polyethylene Glycol also know as PEG or Carbo Wax. Polyethylene Glycol penetrates into the cell structure of the wood. In basic terms, it keeps each cell from shrinking and, therefore, greatly reduces any overall cracking. Artifacts should be submerged for a sufficient period of time that allows full penetration. For example, a wood dead eye may take six months, a wood rib one to two years. Polyethylene Glycol can be purchased at chemists shops, but it is costly.

Another method, which is not scientific by any means, may be used at the reader’s discretion. After the rinse stage which should last from two to 12 months depending on thickness, completely dry the object by using an alcohol bath. Next, coat it heavily with clear polyurethane. The artifact will shrink and crack but hopefully not too badly. The polyurethane coating will also protect any ink writing on the artifact. For dead eyes it is often acceptable to just clean and then coat the wood with linseed oil. The thin oil penetrates deep into the wood and prevents most cracking. This method is only recommended for dead eyes because most dead eyes are made of lignivite, a very hard durable wood.
Photo: Dan Berg with a dead eye recovered from the Cornelia Soule Shipwreck. Steve Jonassen with Date box from the Iberia Shipwreck.

29. Juni 2009 Museum, Wracks (wrecks)

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