Fixing Problems - How to Fix Paint, Mud Cracks, Loss of gloss Etc
Fixing Problems
What causes flaking and blistering of paint on exterior brick and masonry surfaces?
The most common causes are moisture beneath the paint film and paint applied over dirt, oil, grease or onto a poorly prepared, powdery surface. Water-based coatings may blister if applied over surfaces previously painted with solvent-based paints or primed with a solvent-based stabilising primer that isn’t thinned prior to application. To remedy the problem, scrape back all poorly adhering coating to a firm edge and abrade shiny surfaces with abrasive paper. If a solvent-based masonry paint or gloss finish was previously applied, repaint with either Dulux Trade Weathershield All Seasons Masonry Paint or Weathershield Maximum Exposure Smooth Masonry Paint.
What can I do about flaking and blistering paint on wood surfaces?
This is commonly caused by moisture beneath the paint film and by paint applied over grey denatured wood, dirt, oil, grease, polish and other surface contamination. Resin and resin gases from knots can also cause blistering, particularly where dark colours are used on external south facing surfaces. Wood movement, such as in joints in window frames, can lead to splits in the paint, allowing moisture to penetrate the wood and cause flaking. To prepare, scrape back areas of flaking or blistering paint to a firm edge and rub down to feather edges using an abrasive paper. If the problem is extensive, strip completely using a hot air gun or chemical paint remover. Clean out open joints with a stripping knife and dusting brush. Make good all open joints and surface imperfections with Dulux Trade Weathershield Exterior Flexible Filler. Treat knots and resinous streaks with one or two coats of a suitable Knotting Solution before priming with the suitable Dulux Trade Primer. When finishing with water-based gloss or eggshell, use bleached white knotting, as brown shellac knotting may bleed through and cause discolouration.
What is the best way to deal with cracks in plaster?
It is quite normal for small cracks to appear in plaster on interior walls and ceilings, either through drying out in new homes or movement of the building in older homes. Simply cut out the cracks, dust off and fill with a suitable Polycell Trade interior filler. Allow to dry, then rub down smooth and dust off to create a clean, smooth surface for decorating. To ensure even porosity spot prime with a thinned coat of your finish.
How do I resolve blistering of paint on plaster?
Blistering can occur on plaster if you overcoat solvent-based paints such as gloss or eggshell with a conventional emulsion in an area that suffers from high levels of condensation.

To resolve the problem, scrape back the blistered paint until you have a firm edge, feather lightly with abrasive paper and dust off. Now spot, prime and bring forward any bare areas with Dulux Primer Sealer, using Dulux Trade Alkali Resisting Primer on friable surfaces. Finally, repaint the surface using a thinned first coat of water-based Dulux Trade Quick Drying Eggshell followed by one or two full coats.

Why would a paint film over a varnish be chipping?
Paint applied over varnish or some wood stains can sometimes cause chipping if knocked. Varnishes are very hard films and adhesion to these surfaces is difficult. Should this happen, you’ll first need to thoroughly clean down the surfaces to remove all dirt, grease and surface contaminants. Then carefully scrape back poorly adhering or defective paint to a firm edge and rub down to “feather” broken edges. If chipping is severe, the surface will need to be totally stripped back. Dust off prior to repainting.
I decorated my windows with a woodstain a year ago, but it is peeling off the putty, which is dry and cracked. Why is this?
The use of linseed oil putty for glazing in conjunction with Sikkens woodstains is not recommended.

Putty contains drying oils which are necessary in order for the compound to remain pliable. These oils migrate into the timber and oxidise with the atmosphere unless the compound is sealed by a film-forming system, such as a traditional gloss paint.

Sikkens systems are moisture vapour permeable, and therefore do not seal the glazing compound. The resulting loss of the oils allows the glazing compound to dry and crack, causing a failure of the glazing seal. For this reason we recommend the use of approved elastomeric sealants (polysulphide, silicone or acrylic).

What causes blister formations in coating?
Blisters in any coating form as the result of isolated areas of poor/insufficient adhesion of the coating to the surface beneath.

This phenomenon occurs especially in warm and sunny weather, and is often related to the expansion of air in the wood pores, the gassing of gums or resin, or the evaporation of trapped moisture, which pushes the coating film away, shortly after application.

Why does dry paint sometimes look like cracked mud?
It has most likely been caused by applying a thick, heavy coat of un-thinned paint to a textured or embossed surface. ‘Mud cracking’ can also be caused when the air temperature drops rapidly after applying a water-based product, or when over coating an emulsion without leaving sufficient drying time. The solution? Applying one or two thin coats will sometimes fill the cracks. Otherwise the best solution is to strip the surface, repaper and paint.
Blistering and flaking

Cause

This may be due to any of the following factors:

*Moisture trapped beneath the surface of the paint film.

*If the paint is applied over a powdery or friable surface.

*Surface contamination such as dirt, oil, and grease.

*Polish residues on the surface, which impair the adhesion of the paint.

*Excessive movement of the substrate, such as joints, imposing stress on the paint film which can result in cracking which in turn lets in moisture, ultimately resulting in a flaking paint film.

*Resins present in knots causing light coloured paints to discolour or even flake. Resin bleed and flaking is a common problem where dark colours are used on south facing elevations. This is because dark colours absorb more heat than light colours.

Putting it right

All loose material will have to be removed back to a firm edge, spot primed with the appropriate Dulux Primer, and then recoated with the appropriate product. If large areas are involved it will be best to totally strip the surface back to a bare surface and start again.

Bleeding/Staining

Cause

This is usually caused by contamination of the underlying surface by soluble stains.

Putting it right

It is important to seal the original stain by applying a coat of Polycell Stain Stop prior to re-decorating.

Cissing

Cause

This is caused by painting over contaminated surfaces such as wax, oil or polish. The paint cannot adhere to the surface and draws away leaving unpainted areas. This can also be caused by contamination on the brush.

Putting it right

Allow the surface to dry and then rub down using ‘wet and dry’ abrasive paper and a solution of warm water and detergent. Once rinsed and dried the area can be repainted.

Filler shows through the paint

Cause

Filler shows through the paint.

Putting it right

Make sure that all filled areas are rubbed down smooth and level. You will need to prime the filler before painting to prevent subsequent coats being absorbed more rapidly than on other areas. Use a coat of Dulux emulsion thinned 10-20% with clean water. Once this is dried you can apply a full coat of Dulux emulsion.

Foaming

Cause

Using the wrong type of roller can cause foaming of a paint film. Sponge or foam rollers should be avoided with water-based paints. Long pile rollers must be wetted out properly. Foaming happens when air gets into the wet paint film to create air bubbles. When these bubbles burst craters are left on the film surface. Sometimes these craters dry to give an even film.

Putting it right

You will need to rub down using ‘wet and dry’ abrasive paper using water d. The surface should then be rinsed and allowed to dry before repainting. If this is impractical due to the size of area affected the area could be horizontally lined with lining paper and then repainted.

Mud cracking

Cause

The most likely cause of mud cracking is applying a thick, heavy, unthinned coat of paint to a textured or embossed surface such as blown vinyl wallpapers or pebbledash. This is especially true if the paint was applied by brush. Cracking can also occur when Matt paint is applied over Silk if the sheen is not removed from the silk coating.

Putting it right

One or two thinned coats of paints may fill in the cracks. For internal walls, a soft sheen paint is the most suitable product to use. If the affected area is over wallpaper, the best way to solve the problem is to remove the paper and start again.

Powdery or chalky surfaces on outside paint work

Cause

This is caused usually by a wearing away of the paint film by weathering or could be evidence of salts coming out of the surface.

Putting it right

The affected area should be brushed down with a stiff bristle brush to remove as much powdery material as possible before applying a coat of Weathershield Exterior Stabilising Primer. If the powder is due to salts/efflorescence then the surface should be wiped with a dry cloth to exhaust the salts before coating with Dulux Trade Alkali Resisting primer to eliminate staining. It can then be re-painted in your chosen finish.

Cracking of plaster

Cause

This is a common occurrence in new houses and is often the result of plaster drying out or movement of the building.

Putting it right

Cracks should be cut out and all dust and debris removed. The cracks should then be filled using an appropriate filler. The Polycell Polyfilla range has a filler for every size of gap. This can then be painted with your chosen finish.

Mould growth on exterior surfaces

Cause

Moisture is an essential element for the growth of moulds

Putting it right

Affected areas should be treated with Weathershield Multi-Surface Fungicidal Wash. Once rinsed and allowed to dry it can be over coated with your favourite Weathershield Masonry Paint.

Shrivelling and wrinkling

Cause

Shrivelling & wrinkling of new paintwork occurs when the surface of the paint dries too quickly, therefore forming a skin before the paint underneath could dry. It is likely to be worse if a thick coat of paint is applied, especially to horizontal surfaces. It can also occur if a second coat is applied before the first one has dried.

Putting it right

Allow the paint to dry and harden. This may take several days, or weeks, depending on the drying conditions. When dry, rub the surface down using ‘wet and dry’ abrasive paper, and clean with warm water with a little detergent added. Rinse the surface with clean water and allow to dry before repainting. If you are unable to wait for it to dry it would be best to scrape off the tacky paint taking it back to a sound, dry surface.

Rain spotting

Cause

Depressions or surface blemishes in the paint film. A common cause is rain that has fallen on the surface before the film has had chance to fully dry.

Putting it right

When the surface is thoroughly dry the affected surface will need to be rubbed down using ‘wet and dry’ abrasive paper. It can then be re-coated.

Loss of gloss

Cause

Loss of gloss is normally only noticed with high gloss paint & varnishes. It is caused by the settling of dew or condensation on the paint shortly after application. This is often a problem when painting out of season, or in areas of high condensation like bathrooms.

Putting it right

When the surface is thoroughly dry the affected surface will need to be rubbed down using ‘wet and dry’ abrasive paper. It can then be re-coated. This should only be done once the conditions improve or when the condensation problem is resolved.

Yellowing on radiators

Cause

Conventional solvent based gloss paints discolour due to the effects of heat.

Putting it right

There are two options to prevent it happening. Firstly, paint the radiator the same colour as the wall as yellowing is much more noticeable with white paint. Alternatively use Hammerite Quick Drying Radiator Enamel (White or Magnolia) or Radiator Enamel (White).