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SPECIALTY PLASTER FINISHES

White plaster is a combination of white marble sand or

dust (calcium carbonate), white portland cement and

water. As the plaster cures, referred to as hyrdration,

calcium hydroxide (lime) is formed as a by-product. This

calcium is in the “cream” or the surface of the finish, the

plaster dust. This is the softest and most vulnerable

element of the finish as it is highly reactive to the water

chemistry, soluble in nature and takes months to fully

cure. Today there are a variety of specialty finishes

available beyond the traditional white plaster or marcite mentioned previously. These finishes

use unique additives and materials mixed into a plaster application to offer a variety of color

and material options as well as increased strength and chemical resistance. Polymers and

Pozzolans, Ceramic, Quartz and exposed aggregates are a few of these innovative admixtures

that enhance, protect or replace the weakest link in traditional plaster, the calcium. In doing so

this greatly reduces the threat of staining, etching, mottling, checking, discoloration and other

concerns typically associated with white plaster.

Polymers

- as well as silicones, protect the finish during the hydration (curing) process.

They increase hardness, improve bonding and reduce water penetration.

Pozzolans

- are used to convert the calcium hydroxide in the plaster into a less soluble cement

compound for a more durable finish.

Adding one or more of these components may be done to enhance a traditional plaster finish

or they may be combined with quartz, ceramic, or pebbles to create one of the many specialty

exposed aggregate finishes described on the following pages.

Quartz

- As mentioned earlier, traditional white plaster uses a marble sand or dust as the

aggregate. If you remember back to chemistry class and Moh’s table of hardness- (running on

a scale of 1-10; talc being a 1 and diamonds a 10) marble is a 3 and quartz a 7. So, it’s easy

to understand how adding a quartz or stone aggregate would result in a much harder surface

than a marble aggregate plaster. Quartz aggregate, unlike marble, is completely insoluble,

even in the presence of highly corrosive acid, so plasters using quartz are less affected by

fluctuations in the water chemistry.

This mix is a blend of choice quartz (sand, silica) along

with quartz that is colored and fired in a kiln. After the material has set to a particular hardness,

it is washed and brushed with water to expose the aggregate. For further exposure, acid

washing is done.

Ceramic

- New products have taken quartz aggregate and bonded with an exterior ceramic

coating. This coating – which contains inorganic pigments – provides a wide range of colors.

Color crystals are added to more traditional plaster mixes by replacing a portion of the marble

aggregate. Reducing the marble and consequently the calcium, and adding this highly durable

compound not only provides many color options it provides a longer lasting more durable finish

with higher resistance to chemical balance and mechanical abrasion.

COLORED PLASTER NOTE

:

All plaster finishes are subject to mottling, and shade variations

or discoloration. Colored plasters are even more likely to exhibit these traits.

Uneven shades

of color, streaking and pigment stains are not uncommon or considered a defect in colored

plaster pools, the darker the color the more this holds true. Also, variations of shade will exist

between color sample chips and mixed plaster and the color may fade completely or grow

gradually lighter over time. Once again, the best defense is closely following the start-up

procedures, chemical balance and care instructions for your particular pool finish.