Identify Problems - Dekro Paints

How-to Guides

Identifying and Resolving Common Paint Problems

INTERIOR WALLS

Remove Paint and Varnish

To begin
At least 90% of any repainting is surface preparation. Stripping off old finish can be done in three ways.

  1. With a chemical remover
  2. With heat
  3. With abrasives

Helpful Tips
Use plenty of stripper on the surface of the project and apply evenly- one way – with a brush

Recommended Products?
Apply a single coat of Universal Undercoat to the surface before applying any top coats.

Poor Stain Resistance

What causes poor stain resistance?
Stains and dirt being absorbed by the coating, making cleaning difficult.

How do I fix it?
Incorrect type of coating used for areas prone to dirt contamination. Sheen and water based enamels are better suited for kitchens, playrooms, work areas and other surface areas which are likely to get soiled.

Low quality paints that are porous in nature will be more inclined to staining.

Use stain resistant coatings in areas that are prone to soiling.

Good quality water based emulsion sheen paints should be adequate for most applications. More specialised coating might be required for more aggressive contaminants.

Recommended Products

Dekro Hydrosilk

Dekro Hydrosilk is an adhesion promoted plastic satin finish pure acrylic coating. Dekro Hydrosilk has outstanding interior/exterior durability and is stain and scrub resistant.
Acrylic

Blistering Paint

What causes blistering of paint?
Bubbles resulting from localized loss of adhesion and lifting of the paint film from the underlying surface.

Applying oil-based or alkyd paint over a damp or wet surface.

Moisture seeping into the home through the exterior walls.

Exposure of latex paint film to high humidity or moisture shortly after paint has dried, especially if there was inadequate surface preparation.

How do I fix it?
Remove blisters by scraping, and sanding, and repaint with a quality acrylic breathable interior paint. If blisters go down to the substrate: Remove the source of moisture. Remove blisters as above, remembering to prime before applying the top coat.

Recommended Products

Dekro Super Acrylic

Dekro Super Acrylic is a high quality, washable, matt pure acrylic which dries to a smooth matt finish. Regarded as the most popular grade of emulsion paint. Dekro Super Acrylic may also be applied to metal and wooden surfaces, provided these surfaces have been primed with an appropriate primer.
Acrylic | Concrete | Metal | Plaster | Wood

EXTERIOR WALLS

Foaming or Cratering Paint

What causes foaming or cratering paint?
Formation of bubbles (foaming) and resulting small, round concave depressions (cratering) when bubbles break in a paint film, during paint application and drying.

Shaking a partially filled can of paint.

Use of low quality paint or very old latex paints.  Applying (especially rolling) paint too rapidly.

Excessive rolling or brushing of the paint.

Applying a sheen or satin sheen paint over a porous surface.

How do I fix it?
All paints will foam to some degree during application; however, higher quality paints are formulated so the bubbles break while the paint is still wet, allowing for good flow and appearance. Avoid excessive rolling or brushing of the paint or using paint that is more than a year old. Apply an appropriate sealer or primer before using such paint over a porous surface. Problem areas should be sanded before repainting.

Recommended Products

Dekro Hydrosilk

Dekro Hydrosilk is an adhesion promoted plastic satin finish pure acrylic coating. Dekro Hydrosilk has outstanding interior/exterior durability and is stain and scrub resistant.
Acrylic

Surfactant Leaching

What causes surfactant leaching?
Concentration of water-soluble ingredients on the surface of a latex paint, typically on a ceiling surface in rooms that have high humidity (e.g., shower, bathroom, kitchen); may be evident as tan or brown spots or areas, and can sometimes be glossy, soapy or sticky.

All latex paint formulas will exhibit this tendency to some extent if applied in areas that become humid (bathrooms, for example), especially in ceiling areas.

How do I fix it?
Wash the affected area with soap and water, and rinse. Problem may occur once or twice again before leachable material is completely removed. When paint is applied in a bathroom, it is helpful to have it dry thoroughly before using the shower. Remove all staining before repainting.

Chalking Paint

What causes chalking of paint?
Formation of fine powder on the surface of the paint film during weathering which can cause color fading. Although some degree of chalking is a normal, desirable way for a paint film to wear, excessive film erosion can result from heavy chalking.

Use of a low-grade, highly pigmented paint.

Use of an interior paint for an outdoor application.

How do I fix it?
First, remove as much of the chalk residue as possible, scrubbing with a stiff bristle brush (or wire brush on masonry) and then rinse thoroughly; or use power washing equipment. Check for any remaining chalk by running a hand over the surface after it dries. If noticeable chalk is still present, apply a masonry primer then repaint with a quality exterior coating.

Recommended Products

Dekro Masonry Primer

Dekro Plaster and Masonry Primer is a solvent based alkali resistant primer and sealer for use on new plaster, cretestone, fibre cement and alkaline surfaces.
Masonry | Primer

Cracking Flaking Paint

What causes cracking /flaking paint?
The splitting of a dry paint film through at least one coat, which will lead to complete failure of the paint. Early on, the problem appears as hairline cracks; later, flaking of paint chips occurs.

Use of a lower quality that has inadequate adhesion and flexibility.

Overthinning the paint or spreading it too thin. Poor surface preparation, especially when the paint is applied to bare wood without priming.

Painting under cool or windy conditions that make paint dry too fast.

How do I fix it?
It may be possible to correct cracking by removing the loose or flaking paint with a scraper or wire brush, sanding to feather the edges, priming any bare spots and repaint with high quality acrylic.

Recommended Products

Dekro Hydrosilk

Dekro Hydrosilk is an adhesion promoted plastic satin finish pure acrylic coating. Dekro Hydrosilk has outstanding interior/exterior durability and is stain and scrub resistant.
Acrylic

Black mould, fungal or algae contamination

What causes chalking of paint?
Damp areas receiving little or no sunlight and poor ventilation are susceptible to mould. Painting over an area with previous mould and low quality coatings containing no or low levels of biocides. Reusing opened containers that have received contamination from application transfer and or storage conditions.

How do I fix it?
Determine firstly if the contaminant is dirt or mildew by applying an antifungal wash.  Leave area for 24 hours so that the fungicidal can react and kill all the spores. Wash the surface with clean water and allow drying. Recoat with paint that is protected with dry film biocide.

Recommended Products

Mediguard

Mediguard is a top quality 100% pure acrylic water based coating for the prevention of fungal and algae growth.
Acrylic | Antifungal

Sags, Drips, Tears, Curtains and running Paint

What causes sags, drips, tears, curtains and running paint?
Downward movement of a paint film during application and setting, resulting in an uneven film having a thicker lower edge. For example; rough scratch plaster hollows trap more paint and results in runs.

Too thickly applied coat due to incorrect roller cover or technique.

Paint with poor flow properties.

Incorrectly thinned paint.

Painting in too cold or humid conditions.

Spraying to close to the surface.

How do I fix it?
If still wet; brush or roll out to level.

Dried paint needs to be sanded level and repainted. Make sure that the paint and application technique match the original.

Don’t paint in excessively cold or humid conditions.

Do not overload brush or roller with paint.

Blistering/Bagging

What causes blistering or bagging of paint?
Blisters can be intact or perished and flaking. If not dried out the blisters can be found to be filled with water/liquid.

Excessive moisture ingress at back of paint film.

Painting too soon before the masonry structure has dried. Water based paint exposed to rain, high humidity or dew shortly after the coating has dried.

Poor structural design aspect related to moisture barriers.

How do I fix it?
Remove all loose and flaking paint.

Establish cause of moisture ingress and rectify.

Allow structure to dry out before repainting or if moisture source cannot be removed, a breathable coating  may have to be used.

Recommended Products

Dekro Super Acrylic

Dekro Super Acrylic is a high quality, washable, matt pure acrylic which dries to a smooth matt finish. Regarded as the most popular grade of emulsion paint. Dekro Super Acrylic may also be applied to metal and wooden surfaces, provided these surfaces have been primed with an appropriate primer.
Acrylic | Concrete | Metal | Plaster | Wood

Dekro Masonry Primer

Dekro Plaster and Masonry Primer is a solvent based alkali resistant primer and sealer for use on new plaster, cretestone, fibre cement and alkaline surfaces.
Masonry | Primer

Crazing Plaster Cracks

What causes crazing plaster cracks?
Crazing is a network of fine cracks, usually in a hexagonal pattern, which measure between 5 and 75 mm across each hexagon. They are usually very fine and shallow and do not extend through the whole depth of the plaster and are thus classed as non- structural cracks. ISO/SABS define a hairline crack as one with a width of 0.5mm or less. Cracks larger than 0.5mm are usually a true substrate crack. Generally craze cracks are stable and do not open and close with time.

Crazing is usually the result of over trowelling a rich mix (high cement content) or using a sand containing an excessive amount of dust.

Plaster that is allowed to dry too quickly due to sun, wind, absorbent brickwork and or badly graded sand or plaster applied in layers that are too thick.

How do I fix it?
Apply a fibre reinforced coating to the substrate.

Recommended Products

Dekro Super Fibretex

Acrylic co-polymer emulsion. Super Fibretex is specially formulated with cellulose fibres to give a slight textured appearance and bridge hairline cracks without being too rough.

Flaking Paint

What causes flaking paint?
Top coat flaking with the presence of a friable powdery undercoat.

Painting on powdery substrate such as old chalking paint, skim plasters, gypsum etc.

How do I fix it?
Remove all loose and flaking paint.

Remove friable residue from substrate by means of high pressure spraying.

Recommended Products

Dekro Masonry Primer

Dekro Plaster and Masonry Primer is a solvent based alkali resistant primer and sealer for use on new plaster, cretestone, fibre cement and alkaline surfaces.
Masonry | Primer

Efflorescence in Paint

What causes efflorescence in paint?
The formation of random white powdery salts on the surface which are generally more visible on darker coloured surfaces.

These salts are present in the sand used to make bricks and plaster. If moisture is present, the salts get washed to the surface and the paint film.

Failure to remove efflorescence before painting and or excessive continuous contact with moisture -areas most affected include parapet walls and horizontal landings or areas near ground levels and cracks.

How do I fix it?
Remove or seal the source of moisture ingress if this was the cause. Note: This is best done in dry seasons.

Remove efflorescence by brushing and power washing with copious amounts of water. Allow substrate to dry out for 2-3 weeks. If salts return the washing procedure should be repeated.

Apply an alkali resistant primer to the entire surface

Recommended Products

Dekro Masonry Primer

Dekro Plaster and Masonry Primer is a solvent based alkali resistant primer and sealer for use on new plaster, cretestone, fibre cement and alkaline surfaces.
Masonry | Primer

Mud Cracking of Paint

What causes mud cracking of paint?
Mud type crack patterns in paint film is when the top of the film dries faster than the internal bottom layer and the difference in tension results in cracks.

Cracks are generally large in size ranging from 5-15mm in diameter and they tend to be surface cracks.

Water-based paints applied to hot substrates.

Water-based paint drying under extremely hot conditions.

How do I fix it?
Sand down and recoat in thinner layers at more moderate temperatures.

Allow longer drying times between coats.

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