Dramatic
Plasterwork
Fibrous Plaster in Theatres
David
Harrison
 |
The
Stanley Warner Theatre in Washington DC, fully restored using a
mix of fibrous plaster casts and consolidation, and solid plastering
to new loge boxes. |
The term 'fibrous
plaster' is usually used to describe a thin lightweight modular construction
composed of hessian (or 'jute scrimcloth' as it is also known) soaked
in gypsum plaster and cast in a mould. It is strengthened by sawn timber
laths and ribs which are also used for fixing and support. The technique
superseded solid lime and gypsum plaster for fine decoration in the late
19th century and is the principal form used today for cornices and other
fine decorative work.
The
Origins of Fibrous Plaster
The
various forms of plasterwork, from hand modelled stucco to glass reinforced
gypsum may all contain some kind of fibre for strength, and most lime
mortar ceiling work contains enough animal hair to bind the plaster together
between the lath, contributing to its flexible strength and thus its characteristic
longevity. However, most lime plaster is run or spread in situ, and enrichments
which may be added are usually small solid casts stuck to the background
with a 'slip' of mortar, rather than cast in large sections. This is the
type of work usually referred to in the trade as 'solid'.
The
technique of reinforcing gypsum plaster with hessian or canvas has been
known and used for thousands of years, and probably predates the Pharaohs.
Millar, writing in 1897 (see Recommended Reading), mentions mummers' masks
found in Kahun dating from 4,500 years ago. However, modern fibrous plasterwork
in England can be said to date from Leonard Alexander Desachy's patent
of 1856, which drew on a Parisian recipe.
Fibrous
plaster has a number of key advantages over solid plaster and proved immediately
popular. Fibrous plaster weighs much less and is better reinforced so
mouldings can be prepared in a studio or on site, prior to installation,
avoiding the need to run mouldings in situ. The use of modular cast mouldings
can allow great variety of ornament applied in a bespoke way. For example,
incorporating a stock cherub into a dome made to specific dimensions saves
having to model each cherub from scratch. The result was cheaper decoration
and more of it. Fine plasterwork could now be afforded by more people,
and those who could afford it could afford more of it.
Not
only houses benefited, but also theatres, music halls and other settings
where a grand effect was required with perhaps a limited budget and minimum
take-up of space. Most theatres have accessways behind the facades and
lighting rigs cut through ceilings, and in solid work their lavishly ornamented
plasterwork would weigh so much as to require major structural support,
decreasing the useful space behind.
Speed
of operation on site is another advantage in a theatre. Normally, the
decision making processes - the financing, the architectural and interior
design, and the procurement take so long that the time left for execution
of the project is cramped.
In
the past hundred years, fibrous plaster has come into its own, as increasingly
flexible moulding compounds have made it possible to produce casts with
fine sharp relief, undercut decoration, piercing and inlays, and modern
plasters have increased strength and lightness.
Conservation
in Theatres
The
largest single demand for fibrous conservation today is in theatres, partly
because all theatres, ancient and modern, require that a ceiling safety
licence be granted by the local building office every five years. As the
limited funds available to theatres tend to be concentrated on production
rather than building maintenance, the licence is often the only spur to
looking after some very fine craftsmanship.
Most
theatres will contain a broad mix of building materials and techniques
collected from each era through which they have passed. Fibrous plaster
has been common for the past 140 years, and as the normal life of hessian
scrint is about 80 years, most old theatres require some careful treatment
to preserve their fibrous plasterwork. The structure of a fibrous panel,
being more than half composed of organic material and attached to timber
struts, leaves it highly vulnerable to attack by moisture and all forms
of cellulose-eating moulds and fungi. Once dry rot for example has taken
hold, it can travel through the fabric of a theatre very quickly. The
most important part of fibrous conservation is therefore prevention.
| Simple
measures for prevention are: |
| Regular
inspection, particularly in difficult to reach areas: Debris tends
to accumulate on the upper surfaces of ceilings within the void above.
This space should be cleaned out to allow easy access and to allow
the structure to be readily monitored and maintained, as well as to
reduce fire risk and to keep the weight of debris down. Fall arrest
systems and walkways are essential for safe regular access to roof
spaces and voids and usually their development will need be given
a higher priority as they fall far from the top of most theatres'
budget list. |
| Ventilation: Often ceilings are insulated from behind, cutting heating bills, but
any reduction in the airflow across this space also prevents the natural
drying out of any damp which accumulates from condensation in particular,
encouraging infestation. Difficult corners should be specifically
ventilated. |
| Roof
repair: The roof of a theatre is usually the last place that money
is spent, despite being the most obvious source of water penetration.
If left for long enough, a slipped tile or a blocked gutter can lead
to rampant dry rot, costing millions of pounds to rectify. Again,
a program of regular inspection and maintenance is essential. |
| Liaison
with technical crews of visiting shows: A clear brief is required
explaining what is and is not permissible regarding the fabric of
the theatre. Probably half of all damage to fibrous work in theatres
is caused by crews rigging new shows. For example, the bigger shows
these days often require all manner of drapes, light rigs, walkways
and even people to hang out over the audience. It is a sad fact that
the original suspension points are often obscured by debris, and makeshift
ones are cut by visiting crews whose main thought is for the setting
rather than the venerable fabric of the theatre. At the Royal Opera
House recently, a complete set of suspension points with carefully
designed floral covers was found during conservation which had been
forgotten for years. |
Conservation
and Consolidation
If
the prevention approach has not worked or has been followed at all, then
conservation must take the form of consolidation. However, before any
work is carried out, moulds must be taken of any area likely to be damaged
in the preservation process, including any section showing rot, mould,
water damage or crew vandalism for example.
To
make a mould, the area concerned needs to be cleaned back and front, and
temporarily supported if necessary. There are a number of paste-on moulding
compounds available, with adjustable setting times and hardness. A layer
of the compound is applied and allowed to set. This flexible layer is
then backed with plaster and a framework to ensure that the geometry of
the mould is retained. The plaster back is then removed and the flexible
mould peeled off. This can be used to cast a new section of fibrous plaster
later for cutting into the original.
Conservation
of the existing fabric, assuming that the scrim is still intact, consists
of ensuring that the supports and ties are intact. These will be either
wire wrapped in Hessian/plaster wads, or sometimes, direct fixings to
the framework.
Where
the integrity of the scrim and the fibrous panel itself has been lost,
it is sometimes possible to strengthen it by carefully cleaning the back
of the plaster, applying a consolidant such as Primal, and sticking a
reinforcing layer of hessian over the weak area with casting plaster.
The design of a patch repair such as this should take into account the
need to incorporate any existing timber support, and often additional
support will be required - galvanise or stainless steel sections are often
used to avoid any repetition of mould infestation. Wires
and other fixings can be attached to the strengthened section. Existing
ties can be assisted by cleaning off failed plaster and re-wadding, or
by re-attaching the ceiling end of the tie to its support.
Where
large sections of original plasterwork have been lost or cannot be repaired,
glass reinforced gypsum is often used as a substitute for the original
material, chiefly because glass fibre is not affected by decay to the
extent that hessian is. This material is the direct descendant of Desachy's
imported patent, widely used in modern buildings in much the same manner.
At
the Regent Theatre, Hanley, for example, a mixture of the above consolidation
and repair techniques has been used, but with modern sprayed glass fibre-reinforced
gypsum replacements for the proscenium arch, which was too badly decayed
to keep.
A
wonderful example of theatre conservation is the work being done at present
by Mervin Stokes, David Wilmore and their team at the Gaiety Theatre,
Douglas, Isle of Man.
This
masterpiece of Frank Matcham, opened in 1900, has almost been brought
back to its original condition. Careful conservation of water damaged
fibrous plasterwork gilding and paint finishes has given a new lease of
life to one of the most complete and original remaining examples of the
work of this prolific classicist. His robust fibrous plaster casts of
classical beauties and cheeky cherubs, together with his flair for the
most modern (turn of the last century) traps and other stage mechanisms,
and his sense of sightline and comfort mixed with architectural delight
provide fresh impetus, if any were needed, to the plaster conservator.Here
is work which demands to be conserved, not simply out of respect for the
past, but to keep an original masterwork working and providing the pleasure
it was designed to give.
An
earlier example is the scheme completed in 1858 at the Royal Opera House,
Covent Garden (1732), where a wonderful mix of materials was used to restore
the interior following damage by fire in 1856. Traditional solid lime
and gypsum plaster on lath in the corridors and hand-modelled work in
the Royal Box contrast with Desachy's newly reinvented fibrous plasterwork
in the balcony fronts and slips. Traditional carton pierre or papier ri
(paper mashed up with glue and set in a mould by 1858 a century-old technique)
was used in the enrichments to the vaults, while the German inventor Frederick
Bielfeld was commissioned to use his new pressed oil-impregnated fibreboard
in the great dome. This material, which is adorned with plaster enrichment,
was rolled and pressed into shape on formers, oven baked and fixed in
panels to a timber background. Bielfeld's board has proved to be a very
durable material.
At
the Royal Opera House today we now have some fibreglass lighting hatches
in the same highly enriched dome. This modern material has enabled a functional
improvement to be made in keeping with the appearance of the original
design.
Looking
Ahead
The development of fibrous plaster enabled the mass-production of highly
elaborate decorative elements such as cornices and ceiling roses which
play such a vital role in Victorian and Edwardian interior design. The
chief threats are neglect, accidental damage and damp and decay - particularly
of the hessian backing. To be successful, the conservation of fibrous
plaster needs to look at the problems encountered holistically, within
the widest context of the existing environment. The true aim of conservators
must be to conserve the skills of the craftsman, so that the continuing
development of each trade can inform the preservation of its own history.
Recommended
Reading
- Ashurst
J and Ashurst N; Practical Building Conservation Vol. 3: Plasters,
Mortars and Renders. Gower Technical Press, Aldershot, 1988
- Ashurst,
John; Mortars, Plasters and Renders in Conservation. EASA 1983
- The SPAB pamphlets on plaster and its repair. Society for the Protection
of Ancient Buildings
- Millar,
William; Plastering, Plain and Decorative. 1st edition 1897,
republished Donhead Publishing, Shaftesbury, Dorset 1998
|
© Cathedral Communications Limited 2005 |
