Plasterwork

Following the fall of the Roman Empire, the addition of marble dust to plaster to allow the production of fine detail and a hard, smooth finish in hand-modelled and moulded decoration was not used until the Renaissance.

Around the 4th century BC, the Romans discovered the principles of the hydraulic set of lime, which by the addition of highly reactive forms of silica and alumina, such as volcanic earths, could solidify rapidly even under water.

In the mid-15th century, Venetian skilled workers developed a new type of external facing, called marmorino made by applying lime directly onto masonry.

This was composed of gypsum plaster, animal glue and pigments, used to imitate coloured marbles and pietre dure ornament.

Jackson formed an independent company which still today produces composition pressings and retains a very large boxwood mould collection.

Following this, and as a backlash to the disappointment felt due to the repeated failure of oil mastics, in the second half of the 18th century water-based renders gained popularity once more.

Mixes for renders were patented, including a "Water Cement, or Stucco" consisting of lime, sand, bone ash and lime-water (Dr Bryan Higgins, 1779).

These were made primarily with a cement mix often incorporating fine and coarse aggregates for texture, pigments or dyes to imitate colouring and veining of natural stones, as well as other additives.

Floats, traditionally made of timber (ideally straight-grained, knot-free, yellow pine), are often finished with a layer of sponge or expanded polystyrene.

Wooden laths are narrow strips of straight-grained wood depending on availability of species in lengths of from two to four or five feet to suit the distances at which the timbers of a floor or partition are set.

The quantity used in good work is one pound of hair to two or three cubic feet of coarse stuff (in the UK up to 12 kg per metric cube).

Two barrels of mortar were made up of equal proportions of lime and sand, one containing the usual quantity of goats' hair, and the other Manila fiber.

Roughcasting is performed by first rendering the wall or laths with a coat of well-haired coarse stuff composed either of good hydraulic lime or of Portland cement.

Scratched ornament is the oldest form of surface decoration, and is much used on the continent of Europe, especially in Germany and Italy, in both external and internal situations.

Broad spaces of background are now exposed by removing the finishing coat, thus revealing the colored plaster beneath, and following this the outlines of the rest of the design are scratched with an iron knife through the outer skimming to the underlying tinted surface.

These and similar cements have gypsum as a base, to which a certain proportion of another substance, such as alum, borax or carbonate of soda, is added, and the whole baked or calcined at a low temperature.

For internal walls, two coats is the standard and follows the same method as for external rendering but with a weaker mix of five or six sand to one cement and one lime.

However, due to none of these, cracks may yet ensue by the too fast drying of the work, caused through the laying of plaster on dry walls which suck from the composition the moisture required to enable it to set, by the application of external heat or the heat of the sun, by the laying of a coat upon one which has not properly set, the cracking in this case being caused by unequal contraction, or by the use of too small a proportion of sand.

In older properties, hairline cracks in plastered ceilings can occur due to minor deflection / movement of timber joists which support the floor above.

For ceilings metal lathing require simply to be nailed to the joists, the joints being made with plaster, and the whole finished with a thin setting coat or slab.

So strong is the result that partitions of this class only two or three inches (76 mm) thick were used for temporary cells for prisoners at Newgate Gaol during the rebuilding of the new sessions house in the Old Bailey in London.

Cennino Cennini, writing in 1437, says that fine linen soaked in glue and plaster and laid on wood was used for forming grounds for painting.

There are two main methods in USA used in construction of the interior walls of modern homes, plasterboard, also called drywall, and veneer plastering.

Veneer plastering is a one-shot one-coat application; taping usually requires sanding and then adding another coat, since the compound shrinks as it dries.

The plasterer usually shows up after the hangers have finished building all the internal walls, by attaching blueboard over the frames of the house with screws.

However a texture mix doesn't need to be smoothed out when it starts to set: The first thing the plasterer tends to do is go over all the mesh-taped seams of the walls he is about to cover; in a very thin swatch.

If this happens it is said the mix has "snapped" and is normally due to using old product or various types of weather (humidity or hot days can cause plaster to set quicker).

Retardant is added so that larger mixes can be made, since the texture technique doesn't require the person to wait until it starts to set before working it.

Staying away from the corner he then gets a trowel with a nice banana curve in it and starts to run it over the wall in a figure eight or Ess pattern, making sure to cross all areas at least once.

Modern ornate fibrous plasterwork by the specialist company of Clark & Fenn can be seen at Theatre Royal, Drury Lane, the London Palladium, Grand Theatre Leeds, Somerset House, The Plaisterers' Hall and St. Clement Danes Corrado Parducci was a notable plaster worker in the Detroit area during the middle half of the 20th century.