Solid Plaster

 

Plastering, traditionally in lime based materials is referred to as ‘solid’ in distinction from the lighter weight plaster of Paris and hessian based ‘fibrous’ work. Solid plasterwork includes lath and plaster work, solid casting, run-in-situ moulded work and freehand modelling and has uses both internally and externally. Fibrous plaster, is by nature, a material suitable for interiors alone.

Lath and plaster work
Traditional 3 coat lime plaster on riven oak or chestnut lath is at the core of Cliveden’s expertise. The mortars in this case are strengthened with the use of animal hair which gives traditional lath and plasterwork it’s strength and flexibility. Flatwork is generally undertaken in three coats- a haired ‘scratch’ coat which forms the bond with the wooden laths, a haired ‘float’ coat which levels the work and a fine putty and silver sand ‘finish’ coat to make the ceiling ready for decoration- traditionally with either limewash or distemper.Here at Cliveden our conservators are well versed in the repair of lath and plaster ceilings/walls using bespoke systems which are devised in response to the particular construction and materials of an individual ceiling or wall. Lath and plaster ceilings may often be preserved even when, to the untrained eye, they appear damaged beyond repair.We are also available for the wholesale plastering of either lost original work or new ceilings. Lath can be replaced with expanded metal lath were stipulated 

Lime plaster on solid substrates
3 coat work is also used, in the same way, onto solid substrates such as brick or stone. An additional ‘dubbing out’ phase may be necessary to level out flaws in the substrate. Careful attention should be given to the treatment of structural cracks in the substrate to avoid the development of cracks in the finished plaster. The use of stitching bars and mesh is recommended in structurally unsound areas.

Run In-Situ work
If the ceiling is to be decorative in nature embellishments are either manufactured off site and subsequently fixed to the ceiling or ‘run in situ’ onto fixed armatures with the assistance of wooden ‘rules’ and ‘horses’ – steel templates fixed to wooden frames which are drawn over the surface building up the moulding in layers, guided by the rules. This run work provides the basis for cornices and ceiling ribs, coffers and beam cases and in simple designs forms the ornament of the ceiling. In more decorative ceilings the run work is further embellished with cast ornament fixed in place subsequent to the completion of the run in-situ work. Complex cornices may have several orders of applied ornament

Domes, arches and irregular shapes can all be produced using variations of the above techniques. Great care has to take place at the design stage to allow for accurate setting out prior to work commencing.

Freehand modelled ornament
The most refined technique of all the skills required of plasterers is that of freehand stucco modelling. A sculptor’s sensibility is required in tandem with a plasterers knowledge of the use of materials. The lime putty, marble flour and a large range of other materials (stucco recipes range in complexity and secrecy) that forms the modelling medium creates a flexible material that is difficult to master being relatively quick to set. Stucco modelling is an additive process where layers, increasing in the fineness of the aggregate are applied to the flat plaster surface guided by a ‘pounced’ pricked out drawing. The modeller has a two dimensional guide but must be able to see the final design in three dimensions and work swiftly to achieve a perfect result.

Cliveden Conservation are in the forefront of the resurgence of this skill, once thought lost forever. Developing techniques for the restoration of the ornate plasterwork at Uppark House led to understanding of both method and materials for an art which had fallen into disuse

Solid cast work
Moulds are either taken from existing work or modelled in clay in the workshop. Moulds are made in flexible rubber and cast in plaster of Paris or lime putty/aggregate where historic precedence and materials analysis shows this to be the correct medium. Lime putty casts are turned out of the moulds whilst still flexible and can be ‘tweaked’ to subtly alter appearance and add to the diversity of decoration. Such casts would traditionally have been turned out of wooden carved reverse moulds and form a major and delightful part of the charm of Elizabethan and Jacobean decorative plasterwork.

Plaster of Paris casts are exact replicas of the original model and once set cannot be successfully changed. This precision lends itself to the Classical and neo-classical type of ornament where crispness and repetition are major aesthetic components.

As with all our work we make decisions regarding techniques and materials after a prolonged exercise of research and analysis followed by trials and exemplars.

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