Venetian Plaster and Polished Plaster
The earliest traceable history of architects using Venetian decorative polished plaster hails back several thousand years to the interiors of Mesopotamian buildings where limestone plaster was applied as a base for wall-paintings and frescoes.
We then have to spin the clock forward to the Roman period and we can see the very well-preserved internal walls of Pompeii villas finished in plaster which is based on slaked lime (which is burnt lime mixed with water).
We know much about the Roman plasterers' methods thanks to a document entitled "De Architecture" written by Marcus Vitruvius in the 1400s which describes Roman building methods from before the time of Christ. According to Vitruvius Roman walls were first plastered with two or three coats of a course sand and lime mix. The wall was then finished with three coats of plaster made from a mix of fine marble dust and lime, that when worked correctly, formed a smooth, polished finish. Colours were often added as required while the plaster was still wet. The result was a durable, decorative finish that was easy to keep clean.
The Roman method of plastering became popular in 15th Century Venice where if fitted well with the taste for classical architecture that was in favour amongst wealthy Venetians. Local brick and tile industries provided waste terracotta which was ground up to serve instead of sand, mixed with hydraulic lime and applied to the walls to achieve a surface with an essential "breathable" quality in buildings that were naturally susceptible to damp due to their location next to the Venetian lagoon.
Fine plaster finishes were produced from the ground-up waste from nearby marble quarries which was mixed with lime to produce a style of plaster called Marmorino. This could be left white to mimic a fashionable local stone or treated with paint effects to look like solid marble. The lighter weight of the plaster finish was an obvious advantage for building erected on the unstable ground of Venice.
Fashions change and the use of Venetian plaster fell from favour in the late 19th century. Once again we have a specific individual to thank for the renaissance of decorative polished plaster; it was Carlo Scarpa, an architect, who revived Venetian plaster in the 1950s. Some lower quality modern plasters are made from synthetic acrylic resins while the best quality Venetian plasters still adhere to the age-old formulation of marble powder and lime with some added adhesives to make them more suitable for use on modern building materials.
Application and Usage
Although Polished Plaster is a modern term for updated examples of the tradiional Italian plaster "recipes", Venetian plaster's crucial added ingredient is marble dust. The plaster is applied over a primer or base coat with a spatula or special trowel in many thin layers. The plaster is then polished or burnished with a specialised steel trowel to create a smooth, glass-like surface that give the illusion of depth. If desired the plaster can be left unburnished to give a rougher, stone-like texture. Unburnished Venetian plaster is less durable and more susceptible to damage.
When applied correctly by a trained plasterer, polished Venetian plaster has a hard finish thanks to the element of marble dust used in the mix. This is valuable in situations where marble would be impractical or too expensive to install. Polished plaster is particularly useful on columns or curved sections of wall. The plaster can be easily coloured with organic or synthetic dyes, either to closely mimic the natural colour of an existing marble or to fit in with a colour sheme for which there are no "natural" stone candidates. Polished plaster is essentially an internal finish generally used for walls and/or ceilings and can be made to mimic highly polished marble, limestone or travertine. Polished plaster is often sealed with a protective layer of wax.
Venetian Marble Plastering Courses at Goldtrowel
Goldtrowel offers the complete package in its Venetian plastering courses, the best training, the best facilities, the best result. Based in Essex, they offer real life experience and hands-on training.
Goldtrowel's Andy Marshall says, "It takes time to build up a good reputation and gain credibility and that's what we have done by supplying high quality materials and excellent teaching to the UK market for many years. Many UK suppliers use and sell acrylic-based plasters which should not be considered as authentic Venetian plaster. We are proud to work in partnership with Italian companies to bring you real Italian plasters and expertise proven over many centuries."
Click to view Venetian Polished Plaster Courses
Call Andy on 01708 344 700
Article by Melvyn Fickling
© Adrienne Chinn Directories