Conserving the Theatreland Plan
‘London’s Theatreland’ was a project which begun in January 2004 to conserve over 3000 architectural and engineering plans from 27 West-End theatres. They range in date from the 1880s to the 1980s and were originally submitted to the London County Council and then the Greater London Council for approval when the theatres were first constructed and as alterations and improvements took place. Many of the early plans are signed and dated by the architects such as
Arthur Blomfield Jackson
. Some are executed in ink and watercolour whilst others are the predecessors of the photocopy – photo reproductions such as
wet photostats. These are important because they illustrate the history of plan duplication as well as the history of the theatre. Support from the Heritage Lottery Fund allowed LMA to realise the project; the plans, torn and fragile, were unfit for public use and their packaging also needed attention. It is the job of the conservators to carry out treatments including surface cleaning, flattening, repairing, lining and removing old adhesive tape, so that people can study the plans now and in the future.
The New Theatre: ink and water-colour on tracing cloth
In the architect’s drawing office, many of the original images were drawn on tracing cloth with black ink and watercolour paints. Tracing cloth was a cotton fabric coated with starch and resins which made it translucent. This drawing acted as a ‘negative’ so it was placed over a sheet of paper that had been coated with some light sensitive chemicals and on exposure to sunlight or electric light the image was reproduced on the paper. Different chemicals produced different types of prints.
Blueprints were made by coating the paper with iron salts before covering with the ‘negative’ and exposing to light. The paper was then immersed in water, which developed and fixed the exposed salts. Development resulted in the formation of the pigment Prussian blue which gave the print its distinct colour, with the image appearing in white.
Blueprints are stored in the dark and when they are taken out they fade in the light. When they are put back in the dark they can revert back to the original colour. The image can be destroyed if the print is exposed to alkaline conditions so we have to consider the materials we use when repairing blueprints and how we store them to prevent this.
A Blueprint of the Alhambra Theatre (with red additions applied by hand)
A ferrogallic print was made by coating the paper with a mixture of ferric chloride, ferric sulphate, tartaric acid, gelatine and water, and then with gallic acid, mixed with an additional acid to prevent it from reacting immediately with the iron salts. The paper was then covered with the transparency and exposed to light for about five minutes, after which it was diluted in water to allow the gallic acid to react with the unexposed iron salts, and finally washed. This method produced black or brown lines on a pale violet background, though the ground would deepen in colour if under-exposed.
Ferrogallic print of the Strand Theatre with coloured details applied by hand
Diazotypes were made by coating the paper in ‘diazonium’ salts, based on the azo nitrogen-based dye which was invented in the 1860s. The paper was then placed under the original tracing and exposed to ultraviolet light, which destroyed the salts not covered by the lines of the tracing. The remaining salts were developed using a coupling agent and ammonia to produce the final image, which typically featured soft lines and a mottled background.
To make an aniline print, the paper was coated with a mixture of sulphuric acid and a salt such as potassium bichromate, and dried in the dark. It was then covered with the tracing and put into a sealed box together with blotting paper soaked in a mix of aniline oil and benzene.
The compound covering would react with light to turn green when exposed to the aniline fumes, while the areas concealed by the tracing would be turned blue-black.
Aniline print of Her Majesty’s Theatre
The Photostat (also known as the Lucigraph), introduced in 1909, was a large camera that produced black and white prints from an original drawing. The paper, specially made by Kodak & Co, was coated in a gelatine-based emulsion containing silver salts, and after exposure to light the image needed to be developed and then separately fixed before being washed in a water bath to avoid later discolouration. The resulting prints have a slightly glossy surface because of the coating of emulsion.
Repairing the Paper
In the past if people did not have the training to mend paper objects they would use sellotape. Over the years sellotape will deteriorate and harm the paper it is stuck to; it also becomes very difficult to remove. We want to remove sellotape because the glue will sink through the paper fibres, change the colour, damage the drawing underneath and leave a horrible stain.
As paper conservators we do not use sellotape; instead we use a paste made from Wheat Starch. This paste works very well, and if in a few years time someone else wants to change a repair that we have made it means that they can take it off without damaging the paper.
Sellotape can be removed by gently peeling it off, this works better if the sellotape is older as the adhesive (glue) has dried completely, but if it is newer sellotape the adhesive is still sticky and we need to use a Heated Spatula to help us remove it. This is like a mini iron: it conducts heat which helps to release the adhesive from the paper so we can peel it off.
When we have lots of stickiness left on the paper we have to remove it using a Crepe Rubber, which is the same rubber that you can find on the soles of your shoes. The entire sticky adhesive is collected onto the crepe rubber and removed from the paper, leaving it nice and smooth.
Once the adhesive has been removed there will still be a stain left on the paper, usually a yellow or brown colour. This is a little bit more difficult to get rid off as Solvents have to be used. A Suction Table is used when we are removing the stain, as this draws the chemical through the stain and away from the paper, leaving the object in a much better condition. An extractor is put on to draw the fumes away from our face as we do not want to breathe them in.
Using a Crepe Rubber
Lining a Paper object
When an object becomes very weak or breaks away into lots of fragments it needs to be lined. This means that a very thin piece of paper is pasted onto the back of the object and it is pieced back together like a jigsaw puzzle. We use special Japanese paper called Kozo to line our objects and also to mend tears. It is special because it is very thin but at the same time very strong.
Did you know that the Kozo paper is made from the bark of a Mulberry Tree found only in Japan?
Lining an object
Tracing paper, also known as transparent paper, used to be used by engineers, architects and builders to draw original plans. It was good to work with because it is translucent, but as it ages it becomes dry, brittle and more fragile than other paper, making it more challenging to repair. We usually house tracing paper objects in a Melinex (polyester) sleeve to protect them from dirty fingers and prevent them from getting more damaged.
A Tracing paper plan before treatment
A Tracing paper plan after treatment and in a melinex sleeve