Sustainable Stories

Prof. Ito reflected on his experience and said, “Once I tried trehalose, I quickly realized it was significantly easier to handle than lactitol.”
With its superior resistance to acid and heat over lactitol, trehalose remains stable, even in acidified, high-temperature impregnating solutions. Another key advantage is its significant increase in solubility with rising aqueous solution temperature, which allows for a higher yield of crystals when the temperature is subsequently lowered.
Trehalose crystals have very low hygroscopicity and can be easily stored after conservation treatment, even in hot and humid regions such as Japan.

Prof. Ito emphasizes, "The simplicity of the process implies high flexibility and ease of application. This was the most appealing aspect of the trehalose impregnation method.”
The trehalose impregnation method allows treatment at lower concentrations for objects with minimal deterioration. Additionally, the solidification approach can be tailored to the objects's condition. For instance, objects like textiles, where retaining the original color is important, can be solidified in a "glass" state, offering higher transparency than a crystal form.
Thanks to these benefits, the scope of conservable objects that can be effectively conserved has significantly broadened to encompass delicate materials like cloth, rope, and lacquerware.
In the case of wood-iron composite materials, such as those with attached nails, the PEG method often leads to iron corrosion due to moisture absorption, causing damage to the surrounding wood after the conservation process. The trehalose impregnation method, however, utilizes its unique properties to prevent such corrosion of iron.

Nagase Viita researchers, highly knowledgeable about the properties of trehalose, provided guidance and advice on the crystallization/vitrification mechanism during this research.

In 2019, Prof. Ito and his research team began conservation work on the large waterlogged wood objects excavated from the seafloor.

The excavated object is a bulkhead plank, a partition board from within a ship that sank during the Mongolian invasion. The Mongolian invasion was a historical event in the Kamakura period (1185-1333) when Yuan fleets invaded Japan in 1274 and 1281.
Takashima Island (Takashima-cho, Matsuura City, Nagasaki Prefecture), located in Imari Bay, is an ancient battlefield of the Mongolian invasion, and many objects of the Mongolian invasion remain submerged on the surrounding seabed.

The bulkhead plank, a large wooden plank measuring approximately 5.6 meters long and weighing around 364 kg, was raised from the seasite in 2002. Since then, it has been stored in tap water at the Matsuura City Buried Archaeological Center for 17 years.

Prof. Ito first fabricated a large impregnation tank to accommodate this bulkhead plank. He filled the impregnation tank with a trehalose solution and submerged the plank, warming the solution to 60-80°C and allowing it to permeate slowly over about two years. Trehalose allowed the impregnation process to be completed in less than half the time compared to the conventional method. The bulkhead plank was removed in March 2021, and after several months of solidification and drying, a surface treatment was applied to complete the conservation process. Yumi Yasuki of the Matsuura City Buried Archaeological Center worked on the project continuously for two years.
The bulkhead plank is currently stored in the workshop of the same center and is available for public viewing. Prof. Ito comments, "It's stored in an environment without air conditioning, subject to significant fluctuations in temperature and humidity, yet there have been no significant issues with its conservation thus far."

To minimize electricity consumption, Prof. Ito drew inspiration from traditional solar water heating systems and adopted the vacuum tube solar thermal collectors. He implemented a hybrid approach that combined this with electric heaters to accommodate nighttime and inclement weather conditions. An experiment using a test machine revealed that the operation hours of electric heaters during the entire process could be reduced to less than 50%. The storage unit was thoroughly insulated to optimize the thermal efficiency of the device created for the bulkhead plank impregnation process. As a result of these efforts, an approximately two-year impregnation process was carried out utilizing natural energy sources.

He heads a study group on the trehalose impregnation method, hosting regular sessions to discuss everything from new research to cases from failed attempts. Nagase Viita researchers join these valuable knowledge-sharing meetings. Additionally, Prof. Ito works on spreading trehalose conservation technology through international collaborations and technology sharing.

Prof. Ito states, "Conservation processes should not require specialized skills. My goal is to develop a method that is accessible and straightforward for anyone, anywhere, with a low risk of failure so we can conserve as much of the hidden cultural properties around the globe as possible. This is the purpose behind my research."

Conserving the precious objects left by our ancestors is a mission shared globally, aimed at future generations. Nagase Viita is committed to furthering this goal by continuing to support research and aid in the conservation of cultural properties, through the development and production of functional materials like trehalose.

Conservation techniques using trehalose for cultural properties are extending their reach.
The Matsuura City Buried Archaeological Center is currently working on conserving a "single stone stock wooden anchor" from the Mongolian invasion shipwreck, which was raised from the Takashima underwater site in October 2022. The conservation process is expected to be finished by the fall of 2025.
Additionally, in Nagaoka City, Niigata Prefecture, the iron shaft of the Jundomaru, a paddle steamer owned by the Edo Shogunate at the end of the Edo period (a designated cultural property of Nagaoka City), was being treated with trehalose under the guidance of Prof. Ito. This is the first time that the trehalose impregnation method has been used for the conservation of a large metal object salvaged from the seabed, and there have already been requests for guidance from overseas.

Prof. Koji Ito conducted technical training on the trehalose impregnation method during a workshop held by UNESCO on October 27-28, 2023. For further details, refer to the press release issued by Tohoku University of Art & Design.