Conservation of the He Tohu documents
The He Tohu exhibition space grew from the need for improved display and storage of these taonga after many years on display in our Constitution Room which no longer provided good storage or visitor experience.
How do you protect 180-year-old documents some of which had suffered in a damp basement and been chewed by rats?
This was the dilemma faced by the current conservators at Archives New Zealand and the National Library as they prepared our nation’s founding documents to go into the He Tohu exhibition in the National Library building in Molesworth Street, Wellington.
In making their decisions, the He Tohu conservators researched the history of past storage, display and treatment, because understanding past approaches, when previous conservators and archivists were charged with caring for these documents, helped inform the preservation decisions for He Tohu.
The documents, being the Treaty of Waitangi/Te Tiriti o Waitangi, the Declaration of Independence/He Whakaputanga, and the 1893 Women’s Suffrage Petition/Te Petihana Whakamana Pōti Wahine, were already fragile, and the team needed to think carefully about how they would be moved and displayed in the new space. Even though they were only moving 250 metres down the road, it took a large team of people and months of planning and specially designed crates to make it happen.
It was important to herald their move for cultural reasons and acknowledge the signatories, their descendants and the staff who have cared for these documents and to maintain the connection between the past and present in the move.
Of most concern to the He Tohu conservators was the dilemma between permanent exhibition of the documents and the lighting that such an exhibition would need.
These lighting concerns are why the He Whakapapa korero/document room is as it is today – the separate room provides physical and cultural preservation measures – it can have carefully controlled lighting and temperature and humidity, while the interactive and descriptive space can have all the bells and whistles that such a significant exhibition deserves. This treasure box or “Waka huia” also provides incredible strength, so that it can protect the display cases within from fire and earthquake. Particular expertise ensured the cultural needs of the documents were met. Prior to construction a whakawātea or ‘clearing the space’ was led by mana whenua/local tribal authority of the land. Mauri stones sourced from places of significance were laid within the document room. The mauri or life-source of He Tohu is concentrated in the stones, a living energy.
Our conservators worked with the team at the National Library to contribute to the design requirements of the display cases. The manufacturing requirements ensured the cases were able to provide controlled humidity and lighting, and the ability to install remote monitoring equipment to monitor the conditions inside the cases in real time. Monitoring is how we manage the long term conservation requirements of the exhibition and how we know that we are continuing to provide the best conditions for these taonga.
The 1893 Women’s Suffrage Petition
The Women’s Suffrage Petition is approximately 274 metres long and weighs more than 7kg. It took four people to lift and carry it in its protective and climate-controlled crate onto a truck for its journey from Archives New Zealand to the National Library in April 2017.
The 1893 Women’s Suffrage Petition scroll is written mainly with aniline inks of many colours and hues. Aniline inks are susceptible to fading, so the conservation strategy for this document allows it to be moved once every quarter, before any light damage can occur. The case is designed with a “back door” so that the rig to which the scroll is attached can be lowered backwards and into a horizontal position. It is quite heavy and requires two people to lower it down safely. Once it is horizontal, the scroll can be loosened enough to move the scroll along to the new pages to be displayed.
Synthetic aniline inks were developed in the 1860s from coal tar, itself a by-product of gas production. It was an accidental discovery during the quest to produce synthetic quinine, used to treat malaria.
Aniline dyes were popular for being more light-fast than previous natural dyes and in the late nineteenth century all coloured dyes were fashionable. But they were sensitive to water, making them likely to bleed. This was used to the benefit of the postal services, who used aniline dyes in stamps to stop them being soaked off and re-used. Much to the annoyance of modern-day stamp collectors.
Purple ink for writing was common as a copying ink in record keeping. and it was used for important documents. Purple ink may have been used on the petition as purple was the colour adopted by the Suffrage movement.
The Petition has been in different sized rolls during its lifetime. Most recently it was in four parts, so they needed to be joined together for the He Tohu exhibition.
All the documents adhere to their backing boards in the same way. But with He Whakaputanga it is even more important that the document is secured safely as it is displayed vertically.
The photo on the left shows the mounting process. Here we are inserting the conservation hinges to secure the documents. On the right the original two sheets are at the front and the replica documents displaying the back of these sheets behind. They are laid out like this while the hinges dry.
The two sheets of He Whakaputanga are on good quality paper though it is a bit damaged and fragmented at the edges. The paper is lightweight so there weren’t any issues with presenting the pages vertically. We considered many options, including non-adhesive options, but these had both conservation and aesthetic limitations. We decided to use a traditional Japanese paper/wheat starch paste hinge mounting system to attach the documents to the acid free backing boards. This is a common technique used widely by conservators in museums and galleries for mounting paper material. The process is fully reversible, and the documents continue to be monitored closely by conservation staff.
The most challenging risk to manage for long term preservation of the documents is light exposure causing permanent fading, colour change or damage to the documents. It has been our attempt to manage this risk that has had the most impact on the exhibition design, the inclusion of a separate document room and lighting system.
Our aim is to eliminate unnecessary light exposure and to ensure the best quality light and viewing experience. He Whakaputanga is almost twice as light sensitive as the Waitangi Sheet of the Treaty of Waitangi so to keep light levels below the exposure limits set, we tested different lighting and viewing scenarios. By adjusting colour temperature, minimising glare and viewing positions we aimed to find the optimum combination to keep light levels lower without compromising the viewing experience.
All the documents in the He Tohu exhibition are kept in strict lighting conditions. This is to protect the paper, parchment and inks from further light damage. The Women’s Suffrage Petition has the most light-sensitive inks, so the display regime is different to the other documents in He Tohu: we protect the petition by changing the pages on display four times each year.
The other documents are more light tolerant than the Women’s Suffrage Petition. But they remain in the dark until the visitor presses the light button, to protect them from any unnecessary light exposure. It is calculated that the documents can be on display for the full 25 years of the exhibition, and not risk any more fading occurring than is already present within at least 500 years.
The He Tohu conservators track the number of times a light button is pressed, and the total exposure time is measured against the strict conditions in place. Monthly graphs are produced showing the amount of light each document has received and whether it is above or below the amount allowed. Since the exhibition opened in May 2017 there has been no month when any light exposure has gone above the recommended limits.
Temperature and Humidity
Paper and parchment documents are recommended to be stored in cool and dry conditions. In He Tohu the documents are all stored in climate-controlled display cases. The air is conditioned to the preferred relative humidity (RH) before it enters the case. The RH for most cases is around 45%, and for the Women’s Suffrage Petition the RH is set at around 50%.
The temperature in the cases is the same as the document room, 19°C, which is a few degrees cooler than the rest of the exhibition space and the National Library ground floor.
Stable conditions are key to the way the exhibition can protect the documents. Fluctuations in environmental conditions can be very problematic for inks and parchment especially. The paper or parchment needs to maintain its shape to protect the inks from further cracking. We have a facility to match the RH of the room with that of the cases; when we have to open the cases for maintenance, such as the page changes of the Women’s Suffrage Petition, it means that there will be no variation in the RH when the cases are opened.