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ROCKCOTE - GENERAL MAINTENANCE

With regular maintenance a Decorative Coating will deliver a long, trouble free life. Regular maintenance can also alleviate the need to use harsh and dangerous solvents or acid cleaners when a major clean is in order. We would recommend periodic cleaning every 6-12 months. A regular maintenance schedule should involve pressure cleaning or hand cleaning using every day household cleaning products.

Following are basic recommendations on General Maintenance on your external finish .

Pressure Cleaning

80-120 Psi using a fan tip, not a direct needlepoint, as this may lift the sturdiest finish.

Hand Cleaning

Some of the best cleaning results are achieved by scrubbing with a stiff broom or brush, hosing as you go, so as not to allow a firm or dry grime and residue to form. (This can be more difficult to remove than the original dirt.)

Cleaning Fluid

Most household cleaners are safe for general cleaning if all personal safety issues are followed. For stubborn stains, such as rust, CLR Clear is a suitable cleaner.

Mould and Mildew

Heavy wind driven rain periods and high humidity result in perfect conditions for the growth of mildew or mould appearing as unsightly dark stains, sometimes green or purple on the surface. When the mould spores settle on a coated surface, they 'hatch out' and draw nourishment from the coating itself or from dirt on the surface.

As mould reproduces by spores, it is important to apply a residual fungicidal wash that remains on the treated surface and kills mould as it hatches from the spores.

Ensure that the manufacturer's instructions are followed correctly. If you require any further assistance please don’t hesitate to contact us.

TECHNICAL ARTICLES ....

CUTTING IN AND AVOIDING 'PICTURE FRAMING'

What is Picture Framing?

“Picture Framing” is a common problem encountered by painters and is caused by a number of different factors. One of the most common types of Picture Framing is visible when the “Cut In” strips on the borders of a painted area become visible upon drying. The problem becomes particularly more visible on textured finishes and extreme cases have occurred on relatively highly textured surfaces such as Sandcote.

What causes Picture Framing?

The visual effects of Picture Framing are normally due to an excessive or uneven build up of paint. This can be due to the Cut In area drying before being worked in and subsequently an excessive total film build in the border area.

When dry, the thicker film appears glossier than the main wall area. With glancing incident light and viewed at a wide angle the problem can appear much worse than if it is viewed head on. When a cut in area is done with a heavily loaded brush rather than a small roller the paint may lay on top of the texture rather than getting down between the sand and providing an even coating.

Another cause of picture framing is due to incompatibility of colourants with the paint material. Under different levels of application forces between rolling and brushing the final colour may appear different. This problem is also exacerbated by painting when the air or wall temperature is too hot and rapid drying occurs. Not using a primer where it is necessary to use a primer may also aggravate the problem and contribute to overly rapid drying because water and polymer is over absorbed from the paint coating by the substrate.

Another type of picture framing is mostly experienced by spray painters when applying a highly fluid paint film on a horizontal flat surface. If the coating is applied too heavily, rather than run or sag as on a vertical wall, the paint tends to collect more heavily around the borders of the surface thus giving a Picture Frame appearance. For heavier high-build epoxy finishes, this form of Picture Faming can even occur on a vertical surface.

How can I avoid Picture Framing when painting Textured Coatings?

• When painting textures with a roller it is important to use a mini roller, 8cm wide or less rather than a brush. Use a brush only as a touch up measure for difficult sections where a small roller can not be used.
• Apply paint sparingly on the Cut In border area. Use a 12mm pile roller. There is no need to go to a larger roller.
• It is best not to paint in hot weather (above 35 oC) and never paint in direct sunlight.
• Minimize the width of the Cut In border areas where possible.

It is best to work in a team of two and minimise the time between cutting in a border and working in with the wall area so that the cut in area is not allowed to dry.

FADING OF COLOURS
Colour fade is principally caused by the ultra violet component of light decomposing the structure of coloured pigments or altering their chemical constituents. It affects some of the bright, fairly intense colours in the "organic" or synthetic group of pigments used in modern coatings by paint and texture manufacturers. Many of these colours are perfectly suited indoors but change differentially on exterior exposure. Previously many of the bright pigments were compounds of lead, chromium, cadmium and other toxic elements and were quite resistant to UV degradation. Health and Safety legislation now prevents the use of these pigments in architectural coating.

In general, the clean and bright gold, red, pink, orange and violet tones can be expected to fade (or darken) significantly more than the blue, green, and terracotta type colours. We refer to the resistance of a coloured pigment to UV degradation as it's "light fastness" and for individual pigment types this is fairly well known. But in practice very few colours are achieved by using just one pigment or colourant so it becomes difficult to predict the likely fading of a mixed colour, particularly since the actual pigments can react chemically with light with one other, either improving or reducing the potential fade. The degree and rate of fade are very much governed by the actual time of exposure to direct sunlight but over enough time all colours will show some change. Further, colours also have varying degrees of "weather-resistance" and their appearance can be altered by moisture, heat and chemical pollutants in the atmosphere. The actual paint or coating also plays a major part. In coatings using a high quality acrylic resin (eg Rockcote Armour and Toscani), the fade or darkening can be significantly inhibited or retarded.

LEVELS OF FINISH

FOR THE PERFORMACE CHARACTERISTICS OF THE ABOVE FINISHES, REFER TO THE ROCKCOTE SYSTEM CHART

RISING DAMP IN RENDERED WALLS
Rising damp has long been a problem in buildings. Particularly so in buildings with rendered walls, where the applied finish is pushed off the wall by rising damp. Even after the affected areas have been repaired, damage will often occur in the same place or adjacent areas.

The problem of rising damp within the wall itself must be addressed in the design and construction of the building. However, the problem is quite often in the render itself, even though correct procedures have been followed during the construction process. Usually the problem occurs when the base of the rendered wall is subject to continual damp, which rises up the wall through capillary action causing delamination of the applied coating. This problem can be solved through the use of a water-repellent render such as Rockcote Quick Render or Skimcote V6.

These pre-blended cement renders are made water repellent through the addition of special hydro-phobing agents, which restrict the capillary action within the render, thus eliminating the possibility of rising damp.

RUST STAINING ON TEXTURE COATINGS
Be aware that not all brown spot staining is metal rust staining. There are forms of algae and pollen that also appear brown but can also be referred to as “rust staining”. The presence of contamination with metal containing material is usually betrayed by vertical “tails” (coloured stains) going down from the rust spot from 1cm to 5cm in length. These stains are usually brown but can be yellow or green.

Rust spots can be caused by welding and/or metal construction in the vicinity of the textured coating. Iron containing metal particles can become airborne and become trapped on the soft acrylic surface. Rusting then often occurs quite rapidly, within a few weeks and often within days for building surfaces near the ocean.

In the rare instances where rust spots occur they should be rectified as soon as possible to keep wall staining to a minimum and to minimize the cost of rectification.

The wall colour is a lot easier to touch up with small amounts of left over tinted texture or a reproduction of the original match if the problem is caught before any fade or weathering has occurred.

Procedure for the rectification of Rust Staining on Paint and Texture Coatings

• Remove the rusting particle. This can be done with tweezers or the tip of a knife.
• Scrub to r emove the stain or reduce its appearance as much as possible with C. L. R Cleaner (Sulphamic Acid solution). CLR is available at most hardware stores and large supermarkets. Use a stiff bristle nail brush or small scrubbing brush. A rag or sponge will be ineffective.
• Flush the treated wall area with clean water. Prolonged contact with C.L.R cleaner may result in bleaching of the paint.
• Once the surface is dry and at a moisture level of less than 15% WME, t ouch up the surface under each removed rusted particle with an alkali resistant “oil -based” rust inhibiting primer.
• Once the alkali resistant “oil -based” rust inhibiting primer is dry then t ouch up the spot with correct colour top coat. If the original coating is not too old then some of the original left-over paint may be used.

If the wall colour is too old or faded for an “invisible rectification” then it may be necessary to repaint the entire wall surface.

Where possible use two coats of Armour Plus as a topcoat.

Revised March 2008

RUST STAINING ON MARBLE TROWEL-ON COATINGS
Be aware that not all brown spot staining is metal rust staining. There are forms of algae and pollen that also appear brown but can also be referred to as “rust staining”. The presence of contamination with metal containing material is usually betrayed by vertical “tails” (coloured stains) going down from the rust spot from 1cm to 5cm in length. These stains are usually brown but can be yellow or green.

Rust spots can be caused by welding and/or metal construction in the vicinity of the textured coating. Iron containing metal particles can become airborne and become trapped on the soft acrylic surface. Rusting then often occurs quite rapidly, within a few weeks and often within days for building surfaces near the ocean.

In the rare instances where rust spots occur they should be rectified as soon as possible to keep wall staining to a minimum and to minimize the cost of rectification.

Procedure for the removal of Rust Staining on Marble Trowel-On Coatings

• Remove each rusting particle from the dried Marble Trowel-On Coating
• Scrub to remove the stain or reduce its appearance as much as possible with C . L . R Cleaner (Sulphamic Acid solution). CLR is available at most hardware stores and large supermarkets.
• Flush the treated wall area with water. Prolonged contact with C.L.R cleaner may result in bleaching of the Marble Trowel-On.
• Once the surface is dry to a moisture content of less than 15% WME then touch up the surface under each removed rust grain with an “oil -based ” rust inhibiting primer.
• If a tinted primer has been used under the Marble Trowel-On then apply a coat of the tinted primer over the over the oil based primer touch up.
• Touch up the spot with the correct Marble Trowel-On . Ensure the Marble Trowel-On is finished flush and smooth with the rest of the wall. If the original coating is not too old then some of the original left-over Marble Trowel-On may be used.
• When Marble Trowel-On is dry to a moisture content of less than 15% WME, touch up with 1 coat of Rockcote Clearcote. Use a small brush suitable for the small area and do not apply excessively, this should ensure a similar gloss level to the rest of the wall.

If the wall colour is too weathered or faded for an “invisible rectification” then it may be necessary to recoat the entire wall surface.

STRUCTURAL MOVEMENT
The general Rockcote acrylic resin based finishes are not designed for, and have limited ability to bridge cracks in masonry substrates, other than micro or hairline shrinkage cracking.

They cannot be used or expected to bridge structural cracking caused by substrate movement.

In Rockcote Q-Render, Mineral Trowel and other cement based applications; this crack bridging ability is even more limited, due to the rigidity imparted by cement.

VISIBILITY OF JOINTS IN FIBROUS CEMENT SHEETING
With the increasing use of fibrous cement sheeting in modern construction, the requirement to completely conceal the joints where sheets abut one another has become an industry expectation.

Certainly the visibility of joints detracts significantly where the architectural intention is to emulate an uninterrupted masonry wall expanse achieved through use of lower cost pre-fabricated material.

Is the expectation realistic?
Much has been written on the effect of glancing light on interior building surfaces, such as fibrous plaster and gypsum board. In a report on this aspect, the CSIRO advises that for an uninterrupted smooth finish, the surface must be absolutely flat and in practice no building substrates are. (CSIRO 1992 5^th Edn.: Illumination and Decoration of Flat Surfaces).

This is most evident on joints, and the problem of joint visibility under applied finishes is well recognised.

This situation can be exactly translated to exterior wall surfaces.

As well as the increased use of FC sheeting, there is a fashion trend towards the finer textured "Mediterranean" style finishes and a decreasing use of eaves and other components which cast shadows and interrupt sunlight striking the surface.

Again, it is in the joints where the problem manifests itself.

For any number of reasons, including frame movement; sheet alignment; porosity of substrate; as well as jointing products and methods used, the actual joint may be slightly (several microns) raised or lowered compared to the adjoining sheets and/or have a different absorption factor.

Such joints may be clearly evident under glancing light (side lighting), where the incident light is nearly parallel to the surface, and casts visible shadows of the minute uneven projections of the joints.

Where the applied finish is a heavier, high profile texture or flat (no gloss) coating, the light is diffused and unevenness of the substrate is disguised.

With the fine textures and glossier finishes, even down to satin and low sheen, visibility of joints is a frequent result.

This situation must be accepted as part of the overall building system employed and does not constitute failure of the applied finish or untradesman-like application.

The inclusion into building design of visual breaks such as profiles and/or expansion joints assists not only with reducing the effect of glancing light, but also provides natural day-work joints for applicators to eliminate overlapping areas, which themselves are highlighted under side light conditions.

The selection of higher texture finishes and lower gloss top-coats also minimises the problem by diffusing the glancing light, but it should be noted that "flat" or no-gloss paints and membranes compare unfavourably with the glossier versions in dirt/mould pick-up, water resistance and longer term durability.

Reference
CSIRO Australia Division of Building Research 1960, revised 1990: ILLUMINATION AND DECORATION OF FLAT SURFACES, by M. J. Ridge

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