There is a way to soak the wood in hardener or check out these projects,
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forums.aaca.org/topic/325455-repairing-top-frame-wood/
The Science Behind Saving A Sunken Ship - Conserving The Vasa
www.forbes.com/sites/sujatakundu/2016/06...hip/?sh=166c2a9c1cba
This article is more than 6 years old.
Last week, in amongst the Brexit fallout, I did what every sensible Brit would do and left the country for a few days, deciding to pop to Scandinavia at a moment's notice while I still could. Sunny Stockholm's residents greeted me warmly, as did the weather, so I was keen to get inside the confines of an air-conditioned museum. It was in one of these museums that I encountered one of Sweden's national treasures, the rescued warship Vasa.
The Vasa was an immense ship, standing at a height of 52.5 meters, with a length of 69 meters. It was built to impress and intimidate, with brightly painted sculptures and carvings adorning one end of the ship, and two gun decks. Unfortunately, while great detail had been put into the look of the ship, the designers neglected a key factor in the ship's stability. Owing to inadequate ballast, the Vasa was barely 1 km into its maiden voyage on 10th August 1628 before a slight breeze caught its sails. This breeze was enough to cause the ship to lilt, allowing water to pour through the gun ports in the lower gun deck. This further destabilized the ship which rapidly took on more water, eventually sinking in Stockholm harbor.
The Vasa remained firmly stuck in the mud just south of the island of Beckholmen, Stockholm, until 1961 when a team successfully raised the ship. As this was a slow process that involved the removal of water and silt from the ship as it rose above the water, the salvage team was also able to examine the state of the different materials used to make the ship. A problem they encountered early on was the need to keep the ship's timber wet with harbor water, to prevent the wood from drying out. When wood dries out, the water contained within the cells pulls the cells in as it evaporates. If too many plant cells in the wood are shrinking in this way, the structural properties of the wood change. The wood can crack and split and become weaker. Given that this wood had also been subjected to 333 years of microbial attack, the cells could already be a lot weaker, further exacerbating the potential issues of the wood cells collapsing if it dried out.
After 333 years on the harbor bed, the conserved Vasa ship now stands proudl and intact in Sweden's Vasamuseet in Stockholm (Photo Credit: Dr Suze Kundu)
After 333 years on the harbor bed, the conserved Vasa ship now stands proudly and intact in Sweden
It was impossible to keep spraying the ship with water, so conservation chemists set out to find a material that could replace the water component of the cells to maintain the strength of the now waterlogged wood. The material needed to not dry out like the water, but needed to be water soluble to allow it to enter the cells in the wood. Their material of choice was a waxy polymer called polyethylene glycol, or PEG. PEG consists of long chain molecules. The length of the chain determines the properties of the polymer. Solutions of PEG were made and sprayed onto the wood, where it diffused into the cells in the wood, replacing the water component and retaining the cell's bulked up shape. Boron Salts were included in the spray mixture at the start, as they inhibit the growth of any microorganisms that may have infested the wood.
The initial programme of spraying the ship with PEG lasted for 17 years, after which point the ship was gently air dried to ensure that no water-logged areas of wood remained. Finally a finishing layer of a high density, long chained PEG solution was applied to the surfaces of the ship and heat-treated to seal in the previous PEG treatments, and protect the ship from absorbing any more water from its atmosphere.
This method of conservation paved the way for further shipwreck salvages, including that of the Mary Rose which now resides in Southampton. Thanks in large part to the artifacts found on these ships, as well as the materials and designs used in constructing these ships, the Vasa and the Mary Rose conservation projects are just two beautiful examples of how some chemistry know-how can allow us, and future generations, to look back into the past and find out a little more about how our people lived hundreds of years ago.
