Time lapse of the Alchemy Plaster team demonstrating the traditional technique of running a cornice in situ – Brighton Street, Bristo Square Edinburgh.
Until the mass adoption of modern silicone, vynils and polyurethane used to cast lengths of prefabricated fibrous plaster mouldings, cornices, or rather, the linear sections of them, were ” run ” in situ using a running horse. – a metal blade, filed down to the exact shape of the cornice, then mounted on a wooden T piece – which is then run along a baton precisely fixed just below the junction where wall meets ceiling. This then squeezes the plaster in to shape, leaving only the internal corners to be patched in by eye. Enrichment (leaves, flowers, egg and dart etc ), if there is any, is cast separately and stuck on to the main run after it is complete.
The advantages of this traditional method are;
1. The cornice naturally adapts to any undulations, whereas a precast length will not.
2. Other than the corner mitres, the cornice is continuous, whereas a precast has to have joints, excepting particularly short walls. Though many tradesman make a remarkably good job of ‘ sweetening ‘ these, a precast, fibrous plaster cornice is still a facsimile.
3. A run cornice is a solid, integral part of the room.
4. The latitude of adjusting spacing allows any enrichment to be symmetrically placed to meet at the mitres, whereas precast has no such forgiveness.
There are ofcourse circumstances where precast is the only option e.g. when the section is so heavy and voluminous that the structure would be compromised and the labour of mixing and timing, prohibitive, or a tiny reveal, e.g. a chimney breast. In this case, a small section is run, reinforced with hessian and wood and stuck in place.
I rest my case and trowel!
If you have a period property in Edinburgh or elsewhere in central Scotland with plasterwork that needs restoring please do not hesitate to contact Alchemy Plaster for advice or a free quotation.
