THE RELIGHTING OF THE GLOWWORM CAVE

David Williams

In 1977 the Glowworm Cave at Waitomo Caves was administrated by a New Zealand government tourism body called the Tourist Hotel Corporation and being a government department all major maintenance and development involved the government's engineering arm, the Ministry of Works and Development. A ministerial memo dated 29 Nov 1978 noted that "the lighting in the Glowworm Cave will require require upgrading in the next 3 to 5 years." This was the beginning of a long project complicated by delays and financial restraints but finally completed with great success in November last year.

Lighting the cave was first considered in 1905 but there was much debate and controversy. A strong feeling amongst the cave administrators was that lighting would take some of the mystery from the cave and that a cave visit would be too easy. In 1922 advice was sought from Jenolan Caves on their lighting and at last the inevitable happened and an electrical lighting system was installed in 1927. This system was impressive at the time but soon began to decay in the damp cave environment so in 1947 the system was replaced. In the mid 1950s experiments were carried out in coloured and fluorescent lighting and then in 1960 a third generation of wiring and lighting was installed.

Like the previous systems the 1960 project was installed by the Ministry of Works. The three caves Glowworm, Aranui and Ruakuri took seven electricians 12 months to light at a cost of 14,000 pounds. The lighting was robust and well engineered but by the late 1970s the luminaires were beginning to fail and the special daylight blue light bulbs were no longer available. Around this time much research was done on aspects of the management of caves. The growth of plants around lights in caves (lampenflora) was investigated and much work was done on the best type of available lighting to use underground. Much about cave lighting was learnt at this time. One fact was confirmed, the best light for human visitation also suits plants very well.

By 1988 enough information had been accumulated to prepare a planning brief. Within this brief several important principles were established.

1. Emphasis should be placed on the aesthetic quality of light in a cave. Without daylight in a cave there is no 'natural' way to light a cave. Light is artificial and therefore a perfect opportunity for artistic expression
2. The lighting should however complement and enhance the instinctive human responses to being underground. These should be many dark corners and passageways left unlit so that not all of the cave is revealed and something is left to the imagination of the visitor
3. The lighting must not overwhelm the cave's own special lighting display coming from the glowworms
4. The lighting design must provide enough illumination to allow for the safe transit of visitors and be safe to operate and service
5. It must be cost-effective to operate and service and produce minimum heat
6. The light produced from all luminaires must be of a uniform wavelength and be focussed to give sharpness and clarity
7. All power supply, cables and control equipment should be as unobtrusive as possible

Other considerations such as 3 phase and single phase power and emergency lighting were included in the brief. Later that year Elery Hamilton-Smith was asked to visit Waitomo and comment on our lighting plans and other cave matters.

The completion of this brief and Elery's visit did not however mean the job was about to start. Around this time the government announced its intention to sell the Tourist Hotel Corporation and so, as in previous years, almost all spending was contained. When the sale did occur in June 1990 one of the conditions of purchase was the replacement of the lighting system so at least the project was underway.

Two major lighting companies were invited to tender. Unknown to them, a major factor in deciding who was to be successful was how well they listened to our ideas and how enthusiastic they were in putting them in place. Both companies examined the existing system and found that almost all the old power system could be retained and that grafting a new control and luminaire network onto this supply was all that was needed. Independent consultants agreed. In the end Selecon NZ Ltd won the contract. This company had a worldwide reputation in theatre and specialised presentation lighting. They were innovative but also able to listen. The system they chose included small 12 volt luminaires with dichroic quartz halogen lens now common in many lighting situations. These had been designed for all weather outdoor lighting and had the following advantages.

1. The focussed reflectors produced a light of exceptional clarity
2. 12 volts allowed total safety. They could be worked on live and could even be submerged in water
3. The small luminaires, some no bigger than a small torch, could be easily concealed in confined spaces
4. Quartz halogen technology was well proven in the auto industry in conditions even harsher than a cave
5. With good control gear they could be expected to last up to eight times longer than a standard tungsten filament bulbs
6. They produced many more lumens or light per watt than the old bulbs meaning much less heat was introduced into the cave

In October last year work began with a crew of four working through the night six nights a week for 4 weeks. One of our cave guides tried to keep up with these electricians in concealing the newly laid cables but with nearly 2 kilometers of cable this task was impossible and we have just finished this laborious job. Each control station has a fully programmable micro-processor that allows for the fine tuning of each set of lights and the time it takes for the lights to fade in and fade out. Like the luminaires, this technology is widely used in the entertainment industry such as audio visual shows and the theatre. As well as adding drama to the cave setting, the fade-in especially prolongs the life of the bulbs. To date we have changed only two bulbs and these were in the first three weeks of "settling in". This compares with the previous 2 to 3 per week. When installing the luminaires we found we had very few placement options. We were hoping to avoid sites where the lights had been before thus creating a very different cave experience. But this was not possible in many cases because of the glare, it gave us more reason to admire the work and think of those electricians in 1960.

We now have a very modern, safe and spectacular but subtle lighting system in the cave, not as superior or different to the old system as we expected but still a major advancement. Several people have commented that the cave is too dark so we have introduced more light. But we agree with some of the sentiments of the early cave administrators that too much light takes something away from the cave. We want to leave something to the imagination and leave some darkness for the glowworms to shine.