|
ARTIFACT PRESERVATION
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.
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.
LEATHER
 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
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
 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
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
 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.
|
The Shipwreck Diving E-Book
Instant Downloadable E-Book
Shipwreck Diving,
by Capt. Dan Berg is a complete how to book about the sport of
wreck diving. This book is packed with information and heavily
illustrated with over 80 sensational color photographs. |
|
 |
|
