General
I’ve painted over an existing coat of paint and it’s created a wrinkled effect. What’s the solution?
A new coat of paint can sometimes soften the previous coat and cause wrinkling or ‘lifting’.
This can be the result of using a different type of new coating over the existing paint,
or by applying a second coat before the first coat is fully dried.
To solve the problem, to make good.
- If paint is still soft, scrape off, wash with white spirit and recoat to correct film thickness.
- Allow to thoroughly dry (this may take a few weeks). Rub down until smooth and recoat.
- Totally strip back to a clean surface and repaint.
What is the best way to deal with dampness in walls?
If walls are damp, the source of the dampness needs to be found,
e.g. broken rainwater pipes or defective pointing in brickwork.
Walls must be dry before attempting any decoration.
Water stains can be sealed with Alkali Resisting Primer
What can I do about dust and bittiness on a paint surface?
This can be caused by dust and dirt in the air settling on the paint surface; by using a dirty paint brush, or by stirring skin into the paint.
In either case, let the paint dry and harden, then rub down using wet and dry abrasive paper and warm water with a bit of detergent.
Rinse thoroughly with clean water and allow to dry before repainting.
Use only good quality paint brushes and wash out with a little white spirit, making sure the brush is completely dry before starting work.
Avoid stirring skin into the paint by straining into a clean kettle before use.
Can I effectively treat mould and algae on exterior surfaces prior to decorating?
Yes, there is a very effective treatment for these types of vegetable growths, which are most likely to occur in damp conditions or on surfaces with high moisture content.
Before treating, first repair the source of any leaks and check for blocked air bricks and defective or missing DPC. Allow to thoroughly dry then treat affected areas with Dulux Fungicidal Wash.
Leave for 24 hours, wash down to remove residues and allow drying thoroughly before applying coating.
Isolated algae patches on a building exterior may indicate structural defects and should be investigated by a reputable builder or building surveyor.
What is the best way to prepare a surface where the colour has faded?
Surfaces where the colour has faded due to exposure to ultra violet sunlight should be thoroughly cleaned down to removed all dirt, grease and surface contaminants.
Then rub down with a suitable abrasive, dust off and paint over.
Weathered woodwork previously coated with a woodstain or varnish should be thoroughly prepared to remove all grey denatured timber prior to redecoration.
Weathered woodwork previously coated with a woodstain or varnish should be thoroughly prepared to remove all grey denatured timber prior to redecoration.
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. Repaint with Weathershield Primer and Weathershield Arcrylic Exterior Wall Finish.
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.
How can I treat patches of uneven glossiness that appear when using non–glossy finishes on wall surfaces?
This is known as ‘flashing’. It’s a fault in the paint which causes such patches to appear, especially at joints or laps. It is often caused by using paints ready for use rather than thinned or when the surface being paitned has uneven porosity.
You’ll need to repaint the surface with two thinned coats, first cleaning it thoroughly to remove all dirt, grease and surface contaminants. Then rub down with a suitable abrasive and dust off before painting.
Is there any easy way to paint over exterior painted woodwork that is cracking?
In a word, no. This cracking develops as the paint begins to lose flexibility and it no longer expands and contracts with the substrate. The more layers of paint, the worse the problem.
Small areas of cracking can be treated by scraping and rubbing down. But large areas will need to be completely removed with a hot air gun or suitable chemical paint remover. Bare surfaces should be primed with an appropriate Weathershield Primer before painting.
Bubbles on the paint surface have appeared after using a foam roller. How can I correct this?
Foam rollers should not be used with water based paints. If you already have this problem there are two solutions.
- Line with lining paper and repaint
- Rub down smooth and repaint
I get a foaming or frothing effect when using a roller. What causes this?
You’re using the wrong type of roller. For instance, if you use a sponge roller to apply water–based paints,
air is injected into the wet paint film and the air bubbles burst, forming craters on the surface which dry unevenly.
As a rule of thumb, use short pile rollers for flat surfaces, medium pile rollers for medium textures and long pile rollers
for textured surfaces. After rolling, some paints, particularly solvent–based gloss, may need to be ‘layed–off’ with a brush to eliminate foaming.
To repair a foamy surface, thoroughly clean it down to remove all dirt, grease and surface contaminants. Rub down the surfaces with wet and dry abrasion and water or a suitable solvent.
Finally, rinse down and allow to dry thoroughly before repainting. If this is impractical, line the walls before repainting.
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 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.
Why do fillers sometimes cause changes in the colour of the paint finish?- Fillers are absorbent and have a different porosity than the substrate, which can cause variations in colour. Therefore, fillers should be applied as early as possible in the process to avoid variations in gloss, sheen or colour.
- All purpose fillers contian cement and have a high alkali content. Interior grade fillers are based on plaster rather than cement and do not cause changes in colour. To remedy the situation, prime the affected areas with two coats of Speed Undercoat prior to repainting. If the problem is extensive you may need to prime the whole surface to ensure an even finish.
What’s causing the little spots/ cissing of unpainted areas when I’m painting?
The paint can’t adhere to the surface because of contamination by oil, grease, wax or polish. So the paint draws back, leaving unpainted areas, usually in the form of small spots.
To remedy the situation, if the paint is still wet wash it all off, allow the surface to dry and thoroughly harden, then rub it down using wet and dry abrasive paper (or waterproof silicon carbide) and warm water with a bit of detergent.
Rinse the surface thoroughly and allow to dry before repainting.
The defect can also be seen when applying water based paint onto a shinny or glossy surface that hasn’t been abraded properly.
The defect can also be seen when applying water based paint onto a shinny or glossy surface that hasn’t been abraded properly.
I’ve missed a few small areas when applying a coat of paint. Can I just touch them in?
Unfortunately, no. You’ll need to thoroughly clean down the surfaces to remove all dirt, grease and surface contaminants.
Then rub down with a suitable abrasive and dust off before applying a new coat of paint to the affected area.
What should I do about paint that has dried to a soft, cheesy consistency?
A paint film that has dried in this condition is mechanically weak and needs to be completely removed.
Carefully clean down the surfaces and allow to dry before reapplying paint.
What causes fluffy crystal patches and hard, shiny film on walls?
Known as ‘efflorescence’, these effects appear as a result of salts crystallising in materials such as bricks and plaster or render.
The fluffy deposits can be removed with coarse Hessian sacking or by dry brushing, repeated every few days until the deposits disappear.
Hard, shiny efflorescence can be sanded to roughen the surface, then painted over. Conventional solvent–based paints should not be applied on
new buildings where efflorescence occurs for at least 12 months, to allow the surface time to dry out thoroughly. Use Dulux Alkali Resisting Sealer prior to applying any water–based finishes.
Alternatively, use Adhesion Promoting Primer for solvent–based paint.
How do I correct colour variation caused by a wet paint film being disturbed before fully drying?
When pigments have been disturbed in this way, wait until the paint is completely dry. Then reapply paint avoiding touching the wet film.
Certain types of paint appear to produce a shiny bronzing effect. Why is this?
Full coloured paints based on certain pigments, such as Prussian and phthalocyanine blues, can produce a metallic lustre.
To cure this irridescent effect, thoroughly clean down the surface to remove all dirt, grease and surface contaminants, then rub down with a suitable abrasive and dust off before repainting.
This defect is more often seen with spray applied atmosphere paints. To remedy, wet flat and recoat.
This defect is more often seen with spray applied atmosphere paints. To remedy, wet flat and recoat.
What causes ‘blooming’ and how can I avoid it?
This greyish, milky-coloured ‘haze’ on the surface of the paint film is usually caused by moisture attack during drying particularly when painting too late in the day out of season.
Thoroughly clean down the surface to remove all dirt, grease and surface contaminants, then rub down with a suitable abrasive and dust off prior to re-applying paint.
How can I avoid stains or discolorations bleeding through paint surfaces?
Common causes of bleeding from the surface below include old wallcoverings, bituminous paint and creosoted surfaces, so these should be completely removed before painting.
If this is not possible apply one or, in severe cases, two coats of Dulux Trade Aluminium Wood Primer. New creosote or bituminous materials must be aged for at least 12 months before painting.
For staining by metallic inks in wallcoverings or felt tip pens, the surface should be touched in locally with Dulux Trade Alkali Resisting Primer.
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 Alkali Resisting Interior Wall Sealer on friable surfaces. Finally, repaint the surface using a thinned first coat of water–based Dulux Pentalite followed by one or two full coats.
What causes adhesion failure on metal?
Adhesion failure on metal substrates, resulting in blistering, flaking/delamination and corrosion, is usually due either to surface contamination or poor surface preparation.
Among the most common types of surface contamination are grease on new galvanised surfaces and wax residue resulting from the use of chemical paint strippers,
which should be cleaned with an emulsifying Oil and Grease Remover. Dust and general debris should always be vacuumed away before painting. In terms of surface preparation,
the failure to remove millscale from hot rolled mild steel prior to painting can lead to serious problems months or even years later.
Similarly, painting over rust can result in the paint film flaking or the rust breaking through the paint film.
Why would a paint film over a varnish cause 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.
Why does paint stain and discolour on masonry?
There are a number of principal causes:
- Certain types of sand used in the construction or rendering of a building can cause staining, as can certain kinds of brick hollow clay pots or clinker blocks containing soluble salts. Pieces of ferrous metal or iron stone embedded in the material can rust and discolour when the surface is painted. These problems can be treated by sealing the affected areas with Dulux Trade Alkali Resisting Primer when the surface is completely dry.
- Rust staining can occur where old nails are left in the substrate, or a wire brush has been used to prepare the surface. In this case, prime locally with Dulux Trade Metal Primer prior to painting.
- Steel reinforcing in concrete may be too close to the surface and cause rusting. The only effective way to resolve this problem is to get back to the metal itself and treat the cause of the rust. Before repairing the surface and repainting.
Is there an effective treatment for porous surfaces that quickly absorb paint?
‘Hot’ or ‘hungry’ surfaces should be primed overall with very thin finishing coats of emulsion or Primer Sealer prior to painting.
What is ‘grinning’ and how can I correct it?
When an under–surface shows through a painted surface, it is said to be ‘grinning through’. This can happen when a paint fails to completely cover the under–surface, or when an incorrect undercoat has been used for a gloss system.
To correct the grinning, thoroughly clean down the surfaces to remove all dirt, grease and surface contaminants, rub down with a suitable abrasive, dust off and repaint.
An externally applied coating has simply washed off. What would cause this to happen?
If you apply a water–based product in cold conditions (i.e. below 10ºC), loss of adhesion can occur and the coating may simply wash off when it rains. To rectify, thoroughly clean down the surfaces to remove all dirt, grease and surface contaminants.
Scrape back all areas of poorly adhering or defective coatings to a firm edge and rub down to ‘feather’ broken edges. Dust off and re–apply coating.
Can you safely paint over grey (denatured) wood?
No. Failing to completely remove wood that has been exposed to weather and sunlight is a common cause of paint failure. Use a sander or scraper to remove the top surface layer of the grey wood, making sure that the surface is cleaned back to new sound wood.
Prime all bare wood with Dulux Primer or Basecoat before re–painting.
Why does dried 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.
A coating I’ve applied feels sticky and tacky. What’s the solution?
This is often caused by surface contamination such as wax. There's only one thing for it. Completely remove all existing material and carefully clean down the surfaces. Allow to dry, then reapply coating.
What causes mould on inside surfaces and how can it be treated?
Mould flourishes in conditions of high humidity, poor ventilation and on surfaces with a high moisture content. Condensation or poor air circulation is normally the main culprit.
It can be very destructive to paint coatings and needs to be eradicated before applying paint. Treat affected areas with Dulux Trade Weathershield Multi–Surface Fungicidal Wash.
Leave for 24 hours, wash down to remove residues and allow to dry thoroughly. If necessary, repeat the treatment. Improving the ventilation and the use of mould inhibiting paints such as mouldshield will reduce further contamination.
What are the main reasons for paint staining and discolouration on plaster?- Past water leaks or burst water pipes can cause water staining. Before repainting, ensure that the leak has stopped and the surface is thoroughly dry, then spot prime the affected area with Dulux Trade Alkali Resisting Primer.
- Heavy deposits of tar staining from cigarette smoke or soot staining around the chimney breast of open fires are common causes of staining, especially on water-based emulsion paints. To prepare, wash the surface thoroughly with detergent solution and rinse frequently with clean water. Allow to dry, then prime with Dulux Speed Undercoat.
- Conventional solvent–based finishes such as gloss can discolour with age, particularly in areas sheltered from natural daylight, this is known as yellowing. Prior to repainting, wash the surface with a detergent solution, rinse with clean water and allow to dry. It may be more advisable to use a water–based coating for a low light area.
What causes slow drying of gloss and varnish on new paintwork?
With solvent–based paints, it’s usually surface contamination as the result of a poorly prepared surface.
Water–based paints can be slow to dry in damp, cold conditions, or when applied to timbers that are oily by nature, such as teak.
Wet solvent–based paint may be removed using cloths soaked in white spirit. If this is unsuccessful, completely remove the coating using a hot air gun or a suitable chemical–based remover.
To remove slow-drying water–based paints, simply wash off with warm water and detergent solution.
Occasionally, I find that a recently–dried glossy paint film loses its initial gloss. What can I do about it?
Apply another coat of paint, after first cleaning down the surfaces to remove all dirt, grease and surface contaminants.
Then rub down with a suitable abrasive, dust off and repaint.
Why does new paintwork sometimes develop wrinkles?
Known as ‘shrivelling’ or ‘rivelling’, this wrinkling effect can occur when paint dries too quickly, forming a surface skin before the paint underneath can dry properly.
Overcoating a previous undercoat or gloss to soon can also cause shrivelling, as can applying oil-based coatings too quickly at low temperatures.
Before attempting to smooth out the wrinkles, allow the surface to dry and harden, then rub down using wet and dry abrasive paper with warm water and detergent.
Rinse thoroughly with clean water and allow to dry before repainting. If still wet/soft then scrape off and if this is extensive strip all off.
I sometimes get an uneven, patchy appearance when emulsion dries. What’s the best remedy?
This variation of sheen or gloss in dried paint is known as ‘sheariness’ and is often seen in brushed emulsion paints when viewed from a shallow angle.
To correct this condition, often seen with critical lighting on plaster board ceilings, use Fast Matt, Flat Matt or thinned coats.
I’ve heard of ‘saponification’, but what exactly is it?
Saponification occurs when oil–based paints are softened and liquefied by the alkali in plaster when moisture is present.
Materials containing Portland cement or lime are strongly alkaline; gypsum plasters are usually not, but can become alkaline if gauged with lime or if it is brought forward from the backing during the drying phase.
For these reasons, never use oil (solvent) based paints on plaster or masonry surfaces until they are completely dry in depth, then prime the surfaces with Dulux Trade Alkali Resisting Primer.
Where saponification has occurred, completely remove the defective coating, wash down the surface and rinse with clean water. Allow to dry then prime with Dulux Trade Alkali Resisting Primer.
What causes salt staining on plywood and how can I get rid of it?
Salt staining can appear on low build wood stained exterior grade plywood, especially on eaves and soffits. Salts are contained in the adhesive used to bond the layers of plywood together.
Because wood stains are very permeable, they can bring these salts to the surface of the wood. Rainwater will normally remove these salty deposits, except in sheltered areas such as soffits and eaves.
The only way to remove these deposits is to wash them down until they no longer appear.
To prevent this when fitting new soffits adequate ventilation is required and coating the back of the board.
Why am I getting tiny pinholes in the paint film during application?
Pinholing in plaster surfaces is nirmally due to overpainting a very porous surface (either the plaster or a filler) without adequately thinning the priming coat. To remedy, repaint with two thinned coats.
How do I deal with the problems of staining and discolouration of paint on wood?
There are different solutions for each of these problems.
- Staining caused by rust from old nails should be rubbed down to remove the rust, then prime any exposed metal with Dulux Trade Metal Primer before painting.
- Resin bleeding from knots in wood should first be removed with white spirit. Then seal the knots with two coats of a suitable knotting solution and repaint.
- All solvent-based paints such as gloss will discolour or yellow with age. To treat, wash the surface thoroughly with detergent solution, rinse with clean water and allow to dry before repainting.
- If the wood appears to be dirty, particularly around glazing rebates, it may be affected by fungal growth. Clean the surface thoroughly and treat with domestic bleach, or Weathershield Fungicidal Wash, before painting.
Why does paint begin peeling away from a surface in sheets?
Like flaking, peeling results from paint losing its adhesion properties. Often caused by applying thick coatings to poorly prepared surfaces, e.g. unthinned emulsion onto distemper.
The cure is to thoroughly scrape back all areas of poorly adhering or defective coatings to a firm edge. Finally, rub down to ‘feather’ broken edges, dust off and repaint.
How can I remedy sags and runs on new paintwork?
This is usually caused by uneven paint application on broad, flat surfaces, or by over-applying on mouldings or rough–contoured surfaces. Also, failing to join up ‘wet edges’ before they have set can cause excessive film thickness, resulting in sagging and running.
When the paint film is thoroughly dry rub down the sags/runs using wet and dry abrasive paper (or waterproof silicon carbide) together with warm water and detergent. To prevent sags/runs when painting broad,
flat areas, work systematically and cross–brush each section into the next; finally using vertical strokes to gently lay off along the length of the surface.
What is ‘picking up’ and why does it happen?
There are two meanings for this term. One is the process of joining up to ‘wet’ or ‘live’ edges on lapping, thinning the finish coat will help keep the wet edge open;
the other meaning concerns the lifting or softening of a previous coat of paint when applying a new coat, to do this allow to ry and scrape back.
The remedy in both cases is to thoroughly clean the surfaces to remove all dirt, grease and surface contaminants.
Then scrape back all areas of poorly adhering or defective coatings to a firm edge, rub down to 'feather' broken edges, dust off and apply a new coating.
What would cause a poor gloss level on new paintwork?
Condensation forming on the surface soon after application can take the gloss of new paintwork.
This can be caused by painting in cold, damp conditions or painting outside when rain or frost are imminent. Porous under–surfaces can also absorb gloss and make it appear dull.
To remedy, lightly abrade the surface and apply a further finishing coat of paint when conditions more favourable.
Is there a simple way of dealing with powdery surfaces on outside paintwork?
Powdery or chalky old paintwork is caused by the paint film wearing away due to exposure to weather. This natural erosion of the paint coating can often be removed by thoroughly washing down prior to repainting.
If washing doesn’t remove a chalky surface, seal with the appropriate Weathershield Stabilising Primer before painting, or in severe cases remove the chalky surface entirely.
What should I do about a paint film that's been spotted by rain before it fully dried?
There’s only one way to remove depressions or surface blemishes caused by rain spotting. Clean down the surfaces to remove all dirt, grease and surface contaminants.
Then rub down the surfaces with Wet & Dry abrasion, using water or a suitable solvent. Finally, rinse down and allow to dry thoroughly before applying a new coat of paint.
My paint film is showing heavy brush marks after drying. What’s the cause of this?
Coarse or heavy brush marks are most likely caused either by painting onto a very porous surface, or applying paint in warm conditions.
To get rid of the marks, first clean down the surfaces to remove all dirt, grease and surface contaminants. Rub down with Wet & Dry abrasion, using water or a suitable solvent.
Finally, rinse down and allow to dry thoroughly before applying a new coat of paint.
How do you deal with powdery internal plastered surfaces?
Powdery and chalky surfaces are quite common in older properties that have been painted with distemper or white wash. You should completely remove these coatings by washing with warm water and a detergent solution.
Rinse with clean water and change the water regularly. If the surface still remains slightly chalky, seal with Dulux Adhesion Promoting Interior Wall Primer prior to finishing.
Why do both spraying and rolling sometimes produce a mottled ‘orange peel’ effect?
When spraying, insufficient thinning can create this ‘dimple’ effect on a paint coating. The same is true when using a roller, or it could be the wrong type of roller for the product used.
This is normal for such methods of application. To minimise roller mottle, use the shortest pile roller suitable for the finish In any case, to correct the fault rub down with wet & dry abrasion,
using water or a suitable solvent, then rinse down and allow to dry thoroughly prior to applying a new paint coating.
What can I do about powdery and chalky surfaces on external masonry?
Brick and masonry surfaces painted with cement-based paint will eventually corrode and become powdery or chalky. Even unpainted pebbledash or render can become powdery with age. I
n each case, ensure the surface is sound, clean and dry. Remove all loose material with a stiff brush or paint scraper. If powdery or chalky residues still remain, stabilise the surface with a coat of Weathershield Stabilising Primer.
However, don’t use a stabilising solution on new or sound bare rendering that has never been painted.
A well–thinned first coat of the appropriate Weathershield Masonry Paint is usually all that is required.
What can I do to correct a patchy, uneven appearance on a coating?
This is caused either by different levels of porosity in the substrate or by uneven application. Usually, two thinned coats will rectify the problem. Rub down with a suitable abrasive, dust off and apply coating.
How can I quickly test for rotten wood?
Simply run a pen knife blade across the grain. This will only make a small indentation on sound timber, but on rotten timber the blade will sink in. The only cure is to cut out all the rotten wood and replace with sound timber.
Preparation
I want to apply a primer and then a finish coat of gloss to new pine skirting boards. Can you recommend anything?
Use two coats of Dulux Speed Undercoat and then apply one coat of Dulux Gloss Finish. Remember primer only comes in white so extra coats of a vibrant colour may be required.
Which coating should be used on new plaster?- Dulux Alkali Resisting Interior Wall Sealer x 1 coat
- Dulux Pentalite Emulsion Paint x 2 coat
Why is it recommended to apply a thinned first coat of emulsion to a new, dry plastered wall?
It gives the surface a uniform starting point and prevents a patchy appearance and also avoids cracking. Plaster has varying levels of absorbency.
What primer should be used on copper pipes which will be heated?
You don’t need a primer at all. After a thorough clean, apply one coat of a solvent–based product, thinned 10 per cent with white spirit, followed by two full coats.
