What is the difference between traditional plaster and venetian polished plaster?

If you are looking into your options for surface finishes for your home, business, or interior design project, it is likely you have come across Venetian plaster (also referred to as polished plaster, Marmorino plaster, Italian plaster, lime plaster, or marble plaster). If you are not familiar with Venetian plaster, you may be wondering, what is the difference between traditional plaster and Venetian plaster?

In this blog post, we aim to provide you with a brief overview of the differences, looking at the materials, qualities, application process, uses and finishes.

Traditional plaster is typically made from gypsum, lime or cement, and is manufactured as a powder which is mixed with water prior to application.

Venetian plaster, however, is made from a mixture of plaster and limestone dust/slaked lime/lime putty (calcium hydroxide), or marble dust. Some venetian plasters also contain resins or acrylics (plastic dust), however our materials are free from these and low in VOC’s. Water-based pigments are added to the Venetian plaster in order to achieve a wide range of colour finishes.

Venetian plasters contain less chemicals than traditional plasters, are more durable and resilient than traditional forms of plaster.

Venetian plaster finishes are not easily chipped or scratched, and due to this durability, venetian plaster can be an excellent choice for high traffic commercial areas such as restaurants, bars, receptions and lobbies, and in high traffic residential areas such as hallways and bathrooms.

In most modern homes in the UK, there are usually stud walls (metal framework and plasterboard). These stud walls are then usually either tape and joined, or skimmed. When a wall is skimmed, two coats of finishing/Multi finish plaster are applied to a depth of only 2-3mm. This surface is then ready to be painted over.

In certain properties, for example more high end homes or refurbishments, stud walls are generally not used, but instead solid block work. These walls will require a “float and set” finish whereby a backing plaster is applied first, to a depth of around 10-13mm, in order to cover the block work. Afterwards, the surface is skimmed as above.

There are several different types of backing plaster, each of which are more appropriate for certain substrates, but the most common types of backing plaster are British Gypsum’s Hard Wall and Bonding.

With Venetian plaster, the application process will vary in length and complexity depending on which finish is being installed. Application could require anywhere between 2 - 5 coats. Below is a brief outline of the application process for our Marmorino Spatula finish:

• A primer is applied to the substrate.

• 2 x layers of lime putty are applied ‘wet on wet’ to produce a smooth surface, which must be left to dry for between 8 - 16 hours.

• The surface is then lightly sanded to remove any imperfections.

• A third coat is then applied using small irregular trowel strokes, and left until it is 60% - 70% dry.

• A fourth coat is then applied using the same small irregular trowel strokes but this time, as the material dries, it is polished (burnished) using a clean steel trowel to create a highly polished marble-like surface. This layer is then left to dry for between 12 - 16 hours.

• A water-based wax is then applied with a sponge and buffed off, either using a clean mutton cloth or an electric buffer.

Prior to the application of Venetian plaster, the substrate (wall) must be clean, smooth, sanded and stable. The wall surface should be painted with an approved wallboard primer or white matt emulsion mist coat.

The application of Venetian plaster involves the plaster being heavily trowelled as it is finished. The force involved is much greater than with traditional plastering, and will therefore highlight any weaknesses in the substrate at the final stages.

A Substrate Specification Sheet is provided to each of our clients within our tender document, which provides more detailed information regarding how to prepare the substrate prior to our visit.

Whilst traditional plaster is usually applied in order to coat, protect and prepare a wall or ceiling surface prior to decoration, venetian plaster is used as decorative finish in itself. Unlike other decorative finishes such as paint or wallpaper, however, venetian plaster will not flake or fade over time.

Often, a smaller trowel is used when applying Venetian plaster, and Venetian plaster is applied in a less uniform way than traditional plaster, which contributes to the final effect, giving the finish a sense of depth, texture and fluidity.

As you may have seen on our website, there are a wide range of Venetian plaster finishes, varying from Venetian polished plaster, concrete plaster, metallic and colour washed plasters.

Different types of venetian plaster can also be mixed in order to produce more unique, bespoke finishes.

What are the advantages of using Venetian polished plaster?Venetian plaster is a more costly option than traditional plaster and paint for several reasons:

• The ingredients (limestone/marble, plastics, pigments)
• The process by which the raw materials are produced/prepared
• The lengthier and more complex application process
• The greater skillset required for application

You can find more information on Venetian plaster costs in our blog post here.

There are, however, several reasons why the extra cost is always a worthwhile investment, and you can find out more about the many advantages of Venetian plaster in our blog post, here.