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Exhibition texts Maritime archaeology workshop

Instruction

First follow the curved wall on hte right. Then move to the exhibit wall on the opposite side. Continue to the left long wall.

In the middle of the room is part two of the game.

Maritime archaeology workshop

Back from the fieldwork! The next step is processing and interpreting everything that was collected. Sketches, photos and films are put together and analysed. We send samples to various experts for analysis. If something has been recovered, it might need conservation. We piece together the clues and descriptions of ships, places and people begin to take shape.

Nowadays, major underwater excavations are rare. Wrecks and remains are almost always best preserved underwater where they are hardly disturbed. It is also expensive to excavate under water and to preserve waterlogged materials. An option may be to recover an object, document it and then place it back on the seafloor.

Film

The film shows the work of salvaging, examining and then relocating the figure head on Dalarövraket / Bodekull. It was too large to be examined on site.

The film has no text or spoken content.

Preservation under water

Wooden shipwrecks degrade quite quickly in salty seas like the Atlantic Ocean or the Mediterranean. But in the Baltic Sea’s brackish waters, wrecks can rest on the seafloor for many hundreds of years, with hulls intact and masts upright. Organisms that attack wood are rare here – especially the shipworm, which does not thrive in brackish waters. The shipworm is not really a worm, but a bivalve mollusc that leaves winding passages behind when it eats its way through the wood – a termite of the sea.

Other factors that affect preservation are depth, currents, oxygen levels, bacteria and wave movements. Bottom sediments can act as a blanket and prevent material from disintegrating.

Different conditions for preservation, interpretation of graphics with text:

  • In archipelagos and bays, sediment layers often protect wrecks well. But in shallow waters near land, the risk of contemporary salvage is high.
  • At open sea with deep water, wrecks are often well preserved, but also risk of damage by trawling.
  • In shallow waters, waves, ice and weather conditions affect the wrecks.  

Microbial degradation

Wood is usually better preserved in oxygen-poor underwater environments than up on land. But there are bacteria in water that break down wood. Although the shape, colour and surface of an object are preserved, the wood may be very fragile.

Shipworm

At the front end of the worm-like animal are two small shells. The shells are used when burrowing into wood. An invasion of shipworms can totally destroy large wooden structures in just a few months.

Different materials are preserved differently. In the exhibit.

Copper, bronze and brass ferns in marine environments, and iron rust. Glass is layered and can sometimes turn rainbow colored or white. Wood is broken down at different speeds depending on the type of wood.

Conservation

Most materials degrade over time, but their lifespan can be extended through conservation. Many underwater finds need to be kept wet prior to conservation, since oxygen in the air can accelerate degradation. After conservation, a stable climate must be maintained in storage and exhibitions.

The cells of drenched wood are filled with water. If the water dries up, the wood collapses. To avoid this, the water is replaced with preservatives like polyethylene glycol, PEG.

Some metals like gold survive, while other corrode. To prevent metals like iron from rusting, conservators remove harmful salts that have penetrated the material. Afterwards the surface is sealed with varnish or wax.

Films

The preservation of Vasa. Top right.

The film shows the work of preserving Vasa. Salvaging Vasa posed completely new challenges for conservators. The main initiative took over 17 years, but the processes surrounding the preservation continue.

The film has no spoken content or text.

Preservation. Left.

Film with spoken content and subtitles.

Freeze drying and PEG

Small objects of wood and leather, for example, can be impregnated with PEG, a synthetic wax, and then freeze-dried under vacuum. The moisture in the material is transformed directly from ice to vapour, and the shape and size are preserved.

Toggle and rope from Birka. In exhibit.

Toggles were used for various things – this one for joining ropes when sailing. Among the underwater finds from the Viking town of Birka are game boards, wooden bowls and much more. Everything has been documented, photographed, cleaned and freeze-dried.

3D model as a tool

It is almost impossible for a diver to see an entire wreck all at once since visibility in the Baltic is so limited. This is why maritime archaeologists find creating digital 3D models extremely useful since they can quickly document a wreck site in its entirety. With a 3D model, the wrecks can even be experienced and examined by non-divers. You can zoom in, rotate and flip the model. Archaeologists can analyse the ship’s construction, and measure and study details and objects.

The digital model is created from thousands of images. All surfaces and angles must be photographed around the entire object. The images are then processed to create a three-dimensional image.

Three case studies

Here, you can follow three wrecks from discovery to knowledge. One was found in 2017 when the renovation of Skeppsholmen quay in Stockholm began. The navy’s shipyards were located there, and there was a great risk – or chance – of shipwrecks coming to light. The next finding is an archaic wooden wreck found in 1971 outside Ronneby in Blekinge, which only began to be studied after nearly 30 years. 

We will also examine a find that was made off the Blekinge coast in 2006. It turned out to be a German seaplane used in World War II, partially hidden under sediment.

Now we can begin our exciting maritime archaeology work and learn more about the findings!

A steel skeleton

The surface layer has degraded, but the construction can still be discerned thanks to its steel skeleton revealing it is an airplane wreck. The right wing is broken, and in front of the wreck lies the distorted propeller and remnants of the engine.

3D model of the wreck. Interactivity.

  1. An initial sketch of the aircraft wreckage, drawn by a maritime archaeologist to give an overview of the wreck site.
  1. Scattered parts of the aircraft engine and a propeller blade that probably bent when the plane crashed into the water.
  1. Only the internal structure of the aircraft wings, a metal skeleton, is preserved.

An open-mouthed monster

A remarkable monster figure head and carriages for iron cannons was found when investigations of the old treewreck finally started. The ship turned out to be large, 35 metres/115 ft long and 10 metres/33 ft wide.

3D model of the wreck. Interactivity.

  1. Sketch made underwater by a maritime archaeologist when examining the wreck. The cable for the ship’s anchor was run through this hawse hole. 
  1. The figurehead being salvaged from the wreckage. The figure was carved at the end of a timber that stuck out from the ship’s bow.
  1. The ship’s stern section had a sharp V shape, as shown by the shape of the floor timbers at the wreck site.

A royal ship

The upper parts of the ship no longer remain, but the parts below the waterline are very well preserved. The width of the wreck and the length of the keel indicate that the ship was large, likely about 40 metres long. Perhaps a royal ship?

3D model of the wreck. Interactivity.

  1. Several well-preserved cannonballs and other objects were found inside the wreck, indicating that the ship was armed and equipped with guns.
  1. A sketch of the cross-section of the wreck’s hull shows that the ship was robustly built.
  1. The cookroom being excavated. A cookroom, or galley, is the kitchen on a ship, and the hearth here was made from bricks.

Dating with dendrochronology and C14. Exhibit wall.

When maritime archaeologists try to establish the age of wrecks and findings, they like to begin by dating the wood.

In dendrochronological dating, tree rings are analysed in a wood sample, while the carbon-14 dating method uses the carbon isotope C14. C14 is found in all living organisms, but the proportion decreases slowly after death. By measuring the amount of C14 isotope remaining in a wood sample, we can determine when the tree died.

Dendrochronology can be very precise – it is often possible to determine which year the wood was felled, sometimes even where the tree grew. The carbon-14 method is not as accurate, but it can be used on all organic materials.

Carbon-14 sample

When it is not possible to take good tree-ring samples, the carbon-14 method offers an alternative. This carbon-14 sample comes from the log boat that you can see in the very first room of the museum. The analysis showed that the boat was built at the end of the 15th century.

Cross-section of timber. Upper exhibit.

The variation in the width of tree rings from year to year creates a pattern which is unique for the time and place where the tree grew. By comparing the pattern to other samples, it is possible to see when and where the tree grew.

Film, Dating

The film has spoken content and subtitles.

Core sample. Lower exhibit.

This tree-ring sample is drilled from a piece of recovered timber. The advantage of coring is that it is minimally invasive. It is difficult to take core samples under water, so the method is most suitable for recovered material. The sample is dated to 1629-1644.

Scepter

This tree-ring sample comes from a wreck found on Skeppsholmen in Stockholm. The sample is dated to  winter 1613/1614. Archaeological excavation, historical sources and dating together show that the wreck was the Scepter, one of the Swedish king Gustav II Adolf’s flagships.

The osmund wreck

This tree-ring sample comes from a barrel aboard the osmund wreck. The wreck, situated in the Stockholm archipelago, is loaded with barrels containing fist-sized pieces of iron, known as osmund iron. The sample is dated to the first half of the 16th century.

In the drawer: Info graphic about tree ring reference series

Interpretation of text and graphics:

The tree ring reference series are stored in various databases. These are based on wood samplas taken from buildings and such from different times. Overlapping tree ring series can be linked together into long continuous chronologies.

The wider the tree rings, the better the growth season was, with the right amount of rain, sun and heat. The thinner the tree rings, the worse the growth season was.

The tree rings in a wood sample are compared to the reference series. lf it can be matched somwhere into the series, it can be dated.

Typology

Typology is a method of archaeological dating. By studying how a certain type of objects changes over time, you can classify them. In some cases, reference series can be created, with examples of how a particular type of object appeared at different times. Everyday objects can often be dated using typology because many copies of them are made at the same time.

Once the series is determined, you can compare a particular object and place it in the time axis of the reference series. Modern examples are cars and mobile phones. Many of us can immediately figure out whether a car was made in the 1950s or 1990s, or whether a mobile phone is from the 1990s or 2020s.

Deadeyes and glass bottles. Upper exhibit.

A deadeye is part of a ship’s rigging. In the early 17th century they were triangular, in the latter part the shape becomes rounder. The shape of glass bottles also changes. The length of the neck, how round the body is and the shape of the mouth changes over time.

Bartmann jugs

A kind of stoneware, popular in the 16th, 17th and 18th centuries. The German word ‘bart’ means beard, and the jug features a design with a bearded face. The faces get smaller and more grotesque the more recent the vessels are.

Clay pipes

Clay pipes were cheap, had a short lifespan and the models changed quickly. When tobacco first came to Europe it was expensive, so the pipe’s bowl was small. As smoking became more common the price of tobacco decreased, and pipe bowls got bigger.

Fragments are filled in. Lower exhibit.

Often you will find only parts of objects. But for an archaeologist it can be enough. For example, a handle or a foot may be all that is needed to identify at three-legged pot. The fragment is compared to reference collections, and clues to the age of the object can be found.

In the drawer, interactivity

A block puzzle (harder than you might think).

Osteology

An osteologist studies bones from vertebrates. The skeleton carry information about species, age, sex and stature. Traces of injury may also be visible, and sometimes the cause of death can be traced – has the individual died in battle, has the animal been slaughtered and skinned?

Specific activity may leave traces in the skeleton, such as forging or archery. Some bones contain specific information; a pelvic bone can reveal the sex, and heel bone can reveal the withers of an animal.

Bones found on shipwrecks may be from the people on board, the provisions, or from live animals kept on board.

Bone fragment and reference bones

This bone was found aboard a ship that sank in 1709. After comparing it with reference bones, we know it is the right femur of a pig. The upper end of the joint has not become fused, which tells us that the pig was young and still growing.

Microscope with fish vertebrae, interactivity

As fish grow, growth rings form in their vertebrae, a bit like a tree. By counting the rings in a fish’s vertebrae, you can figure out how old it was. How many growth rings can you see?

Bones from Birka

Archaeologists has found many animal bones in the Viking town of Birka in central Sweden. Analyses of the bones have revealed what was eaten and what species of animals were present in the town. Some of the most common animals were likely cows, pigs, and sheep or goats.

One bone type, several species. Upper exhibit.

These are the upper arm bones of a human, a cow, a pig, a sheep or a goat, and a bird. The bones look different because the species have different sizes, look different and move differently.

Film, Osteology

The film has spoken content and subtitles.

In storage. Wall and exhibits with many objects.

Only a fraction of the objects in a museum are displayed in exhibitions. Most are stored in magazines and taken out for research, exhibitions and preservation or to put on loan.

The storage room must be an orderly place where it’s easy to find the right object. The objects are registered in a database, together with information on their location, age, history, discovery site and more.

The humidity and temperature are kept at a stable level, and it must be clean. Dust binds particles that can damage the objects. And did you know that hand sweat contains over 40 corrosive substances? That’s why we wear clean gloves when handling museum objects.

The objects

These objects are usually kept in the Maritime Museum’s stores around Sweden.

Analyze and date. Part two of the game.

The station is designed as three workplaces in the middle of the room. The instructions are given with spoken dialogue, texted prompts and visual illustrations. The content is the same in all three workplaces.

 


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Page last updated: 2021-09-10