The #Rooswijk 1740 Team at Work
On this page:
- How our maritime archaeologists work underwater
- First-aid conservation for the recovered objects
- Recording and conserving the finds for the future
- What environmental materials reveal under the microscope
Stay up to date with the latest discoveries from the Rooswijk on social media using the hashtag #Rooswijk1740.
Maritime archaeologists use many of the same techniques that their land-based counterparts use, but with one major difference - they need special equipment to allow them to breath under the water.
Divers on the Rooswijk are using Surface Supplied Diving Equipment which provides breathing gas to divers through a hose connected to a tank on the surface.
A diving supervisor on the boat can talk to the divers and can direct their dives and ensure they do not stay down too long or come to the surface too quickly.
Maritime archaeologists record the wreck using traditional tools, such as tape measures, pencils and cameras as well as more advanced and specialist equipment like diver tracking systems.
Helmet mounted torches and cameras linked to on-board screens mean dive supervisors can see archaeology as the divers work, often more clearly than the divers themselves. To help them move the sediment that covers the wreck, they use special air lifts that suck the sand away. They are able to finely tune these to ensure important archaeology or tiny objects are not lost.
First aid for conservation
When artefacts are being lifted from a wreck site, they become exposed to higher temperatures and higher levels of oxygen. This means that decay is accelerated. When artefacts reach the surface they have to be kept wet and are not allowed to dry out.
These initial steps, together with the correct packaging and support material, are called 'first aid for conservation'.
Even though water preserves a wide range of materials in often very good conditions, prolonged wet storage is costly and inpractical. The ultimate goal of any conservation treatment is to dry the artefacts. By stabilising them they will then be available and accessible to others.
Recording and conserving the finds
Before artefacts from the marine environment can be dried though, they have to go through a number of stages. First of all, harmful salts need to be washed out. Some materials such as ceramics or metals can often be dried carefully without any further treatment. Other artefacts, such as those made from wood or leather need more stages: impregnation with a special wax followed by vacuum freeze drying. And iron for example benefits from having corrosion layers removed. The finds below are in a freeze drying machine.
As well as stabilising and drying, conservators also investigate and analyse artefacts. They look at how something was made and how it changed. They note and record construction features and decoration.
All this information is shared with the archaeologists and other researchers and together we can use this information to learn about the Rooswijk and the artefacts.
Careful sampling for plant material, insects, bones and shells on wreck sites, particularly from within containers and from the structure and fittings of the vessel itself, can provide information about life on board, cargo and construction and repairs. We hope to learn about the plant, animal and fish foods used to provision the crew, as well as trade items.
Plant material (seeds, leaves, stems and pollen) can also tell us about bedding, flooring, packing material and fuel, as well as the vessel itself (especially ropes and caulking).
Animal bones, insect remains and some molluscs may tell us about pests (rats, fleas, lice, ship worm) and even animals kept on board.
Plants and insects are preserved on submerged sites due to the waterlogged conditions which exclude oxygen and prevent decay. Samples of sediment are placed into bags which will be lifted to the surface and then processed at Ramsgate or at Historic England facilities by sieving through a small mesh (for the recovery of bones, larger plant items and finds) or bucket flotation. Flotation involves separating the organic material (the flot) and inorganic residues (sand and stones) using water. The flot is collected in a very fine mesh sieve and kept wet until it is examined under a microscope. The residue is retained in a bucket and then sorted by eye.