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Flakes, cracks and blisters FAQs

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.

Dulux Trade products are now available in BIM format

Dulux Trade paints and woodcare products can now be seamlessly added to your BIM models as BIM objects - and the process couldn't be simpler. Click the button below to go to the NBS National BIM Library, pick your chosen Dulux Trade product and click the button to download it as a BIM object.

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