Preservation of Waterlogged Items: The Mary Rose - lect 9

Introduction to the Mary Rose

• The Mary Rose is a ship that sank in the 1500s and was raised in the 1980s.

• There is now a large museum in Portsmouth dedicated to preserving the Mary Rose.

• Ellie, a former scientist at the University of Kent, is the head of conservation at the Mary Rose Trust.

• X-ray fluorescence is one of the techniques used to monitor the wood in the ship.

• Alan Chadwick, a retired scientist from the University of Kent, has been a leading figure in the preservation efforts.

Mary Rose Conservation Challenges

• Conserving the Mary Rose artifacts is a race against time to prevent further degradation.

• Researchers from the University of Kent, led by Professor Chadwick Schofield, joined the Mary Rose conservation team in 2009.

• Experiments are conducted at the UK's National Secretron Facility to monitor the ship and its artifacts in real-time.

• Salts forming on woven artifacts when exposed to air, humidity, and elevated temperatures is a significant issue.

• These salts are not only unsightly but also damaging to the artifacts.

• The goal is to understand how these salts form and develop treatments to solve the problem, using diamond tools.

Drying Process and Transformations

• Initial focus was on preparing the ship for drying after conservation treatment.

• Exposing the ship to air during drying can cause transformations of elements in the wood.

• A program of work was set up to monitor change over time and develop protective treatments.

Development of Special Compound

• Researchers from the University of Kent and the Mary Rose team developed a special compound to treat the ship's timbers.

• Current work focuses on incorporating nanoparticles to get them into the water.

Museum and Visitor Experience

• The Mary Rose Museum first opened in 2013 and reopened after a major revamp in 2016.

• The museum attracts up to a quarter of a million tourists each year.

• Visitors appreciate the quality of the conservation work.

• The collection offers personal insights into daily life in Tudor times.

• The museum showcases weaponry and personal items like knitcombs, shoes, and clothing, providing insight into Tudor life.

Engineering and STEM Contributions

• There is a growing focus on highlighting the engineering and STEM contributions involved in the conservation process: from finding and excavating the ship to developing conservation treatments and the museum itself.

Pioneering Science and Technology

• Preserving the Mary Rose relies on pioneering science and technology.

• It is the first time the degradation and treatments of materials in artifacts are monitored in real-time.

• Research led to the discovery of a special compound to treat the ship's timbers.

X-ray Fluorescence

• X-ray fluorescence is a technique used to characterize compounds.

• It is effective for heavier elements (generally above sodium) but not for light elements like lithium and hydrogen, as the energy levels are too small.

• The technique can be applied to any compound to study its elemental composition.

• The University of Kent has a small desktop X-ray fluorescence instrument.

• The video mentions a Signatron, which is a more powerful way of producing X-rays.

• Signatrons can focus the X-rays to examine very small parts and map composition across the surface (x-y mapping).

• The technique can distinguish between different elements and their oxidation states (e.g., Fe^{2+} vs. Fe^{3+}).

Experiment Process

• The process involves bombarding the sample with high-energy X-rays, which knock out electrons from the inner core of the atoms (e.g., 1s electrons).

• This creates a hole, making the atom unstable. An electron from a higher energy level drops into the hole, releasing energy in the form of X-ray fluorescence.

• The energy of the emitted X-ray fluorescence is measured.

Energy Levels

• Energy levels within an atom are referred to as K, L, M, and N shells, corresponding to different energy states.

• Incoming X-rays are tuned to knock out electrons from the lowest energy form.

• The electron in a higher energy level jumps into that lower state, releasing the difference in energy as x-ray fluorescence.

• The energy of the fluorescence is measured by a detector.

Characteristic X-rays

• Each element has well-known and exact energy levels, allowing for precise identification through the measured fluorescence energy.

• By tuning the incoming X-rays, the experiment can be optimized to provide the best information.

• The emitted X-ray is termed characteristic because it allows for the identification of elements present in the sample.

• The X-ray fluorescence instrument can identify elements (e.g., potassium, sodium, iron) and their ratios in a compound, even without prior knowledge of the compound.

History of the Mary Rose

• Built during the reign of Henry VIII, who wanted to create dedicated warships due to concerns about France.

• The Mary Rose was one of the first ships designed and built as a warship from the start.

• It served as the flagship and was successful in several battles in the early 1500s.

• The ship was refitted multiple times, including increasing the number of guns from 78 to 91, which was a common practice but made the ships unstable.

Sinking of the Mary Rose

• In 1545, the French attacked the British fleet in Portsmouth.

• The British fleet of 80 ships was outnumbered by the French fleet of 200 ships.

• The French claimed to have sunk the Mary Rose, resulting in the loss of 700 lives.

• Many experts believe the Mary Rose sank because it tried to turn too quickly with open port doors, taking on water and sinking.

• The ship sank close to Portsmouth Harbour, and the silt in the harbor helped preserve it.

Rediscovery and Raising

• The Mary Rose sank in 1545.

• Attempts were made to raise it immediately, but the technology was lacking.

• The ship was found again in the 1800s, but raising it was still not feasible.

• The ship was relocated in the early 1970s and raised in the 1980s.

• The ship was kept in a warehouse with water being sprayed on it to prevent deterioration.

Lessons from the Vasa

• The Vasa is another preserved ship in Stockholm that sank on its maiden voyage.

• The Vasa sank in 1628 because the King of Sweden insisted on adding a third layer of guns, making it unstable.

• The ship was built by the Dutch, who warned against the modifications.

• The Vasa was preserved in silt in the Stockholm Archipelago.

Waterlogged Wood Problems

• Waterlogged wood can fall apart as it dries out due to holes in the wood.

• The Vasa was sprayed with polyethylene glycol (a cheap and flexible polymer) to fill the cracks and aid in the drying process.

• The Mary Rose also underwent this treatment.

Sulphur Problem

• Deterioration was observed in certain areas of the wood, particularly around iron fittings, due to the formation of sulphur deposits.

Sulphur and Acid Formation

• Bacteria in the silt and wood produced sulphur.

• The sulphur reacted with iron to form iron sulphide.

• When exposed to oxygen, the sulphur turns into sulfuric acid, which corrodes the wood.

• This issue was initially reported for the Vasa and was also found in the Mary Rose.

Nanoparticle Treatment

• Items from the Mary Rose were soaked in a buffer solution with nanoparticles developed at the University of Kent.

• The nanoparticles react with iron sulphide to neutralize the sulfuric acid.

Monitoring Sulphur Levels

• The University of Kent monitors sulphur levels using XRF at the Diamond Synchrotron.

• Small samples from different items and the ship itself are analyzed to monitor the oxidation state of iron and sulphur over time.

• Samples are measured to see if they are deteriorating.

Data Analysis

• Data is collected from the surface of wood samples.

• The sulphur edge is analyzed over time to monitor deterioration.

Practice Questions

1. What is X-ray fluorescence and how is it used in the conservation of the Mary Rose?

2. Describe the challenges associated with conserving waterlogged wood, as exemplified by the Mary Rose and the Vasa.

3. Explain the role of nanoparticles in treating artifacts from the Mary Rose, particularly in relation to sulphur and acid formation.

4. Outline the key historical events leading to the sinking of the Mary Rose and the subsequent efforts to rediscover and raise the ship.

5. Discuss the STEM contributions involved in the conservation process of the Mary Rose, from excavation to museum design.