Conservation of the He Tohu documents
The He Tohu exhibition space came 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.
Of most concern to conservators involved with designing the new He Tohu exhibition, was the dilemma between permanent exhibition of the documents and the lighting that such an exhibition would need.
These lighting concerns are why the document room as it is today – the separate room itself provides 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 would protect the display cases within, from fire, earthquake.
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 closely monitor the case conditions. Monitoring is how we manage the long term conservation requirements of the exhibition and how we can 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. 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, a by-product of gas production. It was an accidental discovery during the quest to produce synthetic quinine, used to treat malaria.
Purple dyes were popular for being more light-fast than previous natural dyes. But they were sensitive to water, making them likely to disappear. 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. It was thought that it was more permanent than other inks and so it was used for important documents. In the late nineteenth century all coloured dyes were fashionable. 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 are stuck to their backing boards in the same way. But with He Whakaputanga it is even more important that the document stays in place as it is displayed, vertically.
The mounts were prepared from high quality 8-ply acid-free museum board. The two sheets were adhered to the boards using conservation grade paper hinges and starch paste. The work took place in our conservation laboratory.
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 drying the hinges.
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 wasn’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 acid free backing boards. This is a popular technique used widely by conservators in museums and galleries for mounting paper material. The process is fully reversible, and the documents are 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 exposure 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 best 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, because of this the lighting conditions are different to the other documents in He Tohu. We protect the petition by changing the pages on display 4 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 too much extra light exposure. It is hoped that this means the documents can be on display for the full 25 years of the exhibition.
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 50%.
The temperature in the cases is the same as the document room. The temperature in the room is set to be 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 must open the cases for maintenance, such as the page changes to the Women’s Suffrage Petition, this means that there will be no variation in the RH when the cases are opened.