Problems with paint


Blisters top

    Blisters mostly occur on exterior woodwork, blisters can vary in size from pinheads to large areas. The cause is moisture in the wood or on the surface, trapped between coats of paint, or where there may be resinous knots in the wood. Another less common cause is painting over a soft, thick coat of existing paint. The action of very strong sunshine when any of these conditions exist is likely to cause blistering.

    Dark colours tend to blister more than light colours as they absorb more of the sun's energy and so heat the surface.

Prevention

    Try to paint external woodwork towards the end of the summer when, ideally, it should have dried out completely. If this is not possible, try to paint in dry, warm conditions after a period of dry warm weather - one day of sunshine will not dry the timber sufficiently. Don't paint immediately after rainfall or washing down, unless the surfaces are thoroughly dried off - light use of a heat gun can remove surface moisture. Strip off any thick, soft paint before you start applying new coats and always apply knotting to all resinous areas on the bare wood.

Remedy

    Cut off the surface of the blister and with fine wet and dry glasspaper rub back to a sound surface - or to bare wood if blistering is extensive. Apply knotting and primer as necessary, fill depressions with fine surface filler and apply under and top coats.


Brush marks top

    These can be seen in the finished paint. The cause is insufficient rubbing down of the old paint surface, faulty application (applying the paint too thickly and not brushing out correctly) or using poor Quality brushes.

Prevention

    Carefully prepare the surface, making sure poor paint is rubbed right back. Apply the paint evenly and finish brushing out in the direction of the grain. Slightly thin excessively thick paint before use and always use good quality brushes.

Remedy

    If these are on the fascia board of a two storey building, you may decide to leave them; not many birds will complain !

    Allow the paint to harden for several days; even though it may seem dry after a few hours only the surface will have dried. Rub down the affected areas with fine wet and dry glasspaper, wash with clean water, dry thoroughly and apply a new top coat. Skin often forms on old paint in cans. If you spot it, carefully lift it away before stirring; if it is extremely thin you can stir it into the paint and then strain the paint through fine muslin or mesh.

Dull gloss top

    Dull finish occurs if thinners are used wrongly, the surface is not properly primed or undercoated, the undercoat is not given sufficient time to dry or the final coat is overbrushed. It can also appear where the top coat is applied in damp or frosty conditions; or where the finish is subjected to dampness or frost during the early stages of drying.

Prevention

    Prepare thoroughly. Leave the undercoat to dry for the recommended time, avoid using a thinner in gloss paint and do not apply in damp or frosty weather conditions.

Remedy

    Allow the paint to dry, then rub down lightly with fine glasspaper, dust off and apply a new top coat.

Flaking top

    Paint falling away from surface is due to poor preparation or bad use of primer. It can take weeks to show and will usually be confined to small areas on the surface.

Prevention

    Thoroughly clean and prepare the surface. If stripping back to bare wood apply a suitable primer. When emulsion paint flakes from walls or ceilings it normally indicates that you have applied the paint over distemper. Before painting, remove all distemper by washing and scraping off the loose material, covering the remainder with a coat of suitable sealer.

Remedy

    If flaking occurs in small patches, strip these areas back to the bare surface, fill depressions with fine surface filler and repaint. If flaking is extensive, however, you will have to strip off the whole lot and start again.

Grinning top

    The colour of the previous coat shows through the dry paint film indicating another coat is needed. Grinning may also occur if you use the wrong undercoat (type or shade), do not stir paint sufficiently, thin it too much or overbrush the topcoat.

Prevention

    Use the correct undercoat and the recommended number of finishing coats. Make sure you stir the paint according to the manufacturer's instructions. Never brush out the top coat too far.

Remedy

    Apply extra top coats as needed.

Pimples top

    Particularly noticeable in shiny, gloss surfaces, these are caused by specks of dust that may have been on the surface, on the brush or in the paint itself. Or a very fine skin on the surface of the paint in the can (especially non-drip gloss) may have got broken and worked into the paint on application.

Prevention

    Make sure the surface is clean and free of dust at each stage of the work: after burning off or rubbing down and before applying primer, undercoat and top coat. Clean the surface with a tacky (resin- impregnated) rag or a clean, lint-free one dampened with mentholated spirit. Pay particular attention to corners since pockets of dust here, though difficult to clean with a rag, will be picked up on the brush and spread across the surface. Use a pointed stick under rag to ensure every particle of dust is removed from corners. Paint brushes must be cleaned , even new brushes need rinsing before use as bristles will contain some loose hairs. Before opening a can of paint, wipe the rim around the top of the can to remove particles that might otherwise fall into the paint.

    It is a good idea to transfer a small amount of paint into a clean kettle or other container to work from. If dust falls into the kettle then only a small amount of paint will be affected.

    Clean the room thoroughly before starting work and allow time for dust to settle before using paint. When painting outside, avoid windy days and spray water underfoot to keep any dust from being disturbed.

    Don't try to remove specks while the paint is still wet as you will only add to the problem by smearing the paint.

Remedy

    Allow the paint to harden for several days; even though it may seem dry after a few hours only the surface will have dried. Rub down the affected areas with fine wet and dry glasspaper, wash with clean water, dry thoroughly and apply a new top coat. Skin often forms on old paint in cans. If you spot it, carefully lift it away before stirring; if it is extremely thin you can stir it into the paint and then strain the paint through fine muslin or mesh.

Runs, sags and wrinkles top

    Fine lines or drips on a painted surface result from poor application. Wrinkles are likely to occur on thick, sagging paint.

Prevention

    Do not overload the brush and always brush out each application before adding another. Look at the paint five minutes after application; it may still be possible to brush out any runs.

Remedy

    If you notice runs before the paint has started to dry, brush them out lightly; if the paint is drying, you will smear the surface.

    Allow the paint to harden for several days; even though it may seem dry after a few hours only the surface will have dried. Rub down the affected areas with fine wet and dry glasspaper, wash with clean water, dry thoroughly and apply a new top coat. Skin often forms on old paint in cans. If you spot it, carefully lift it away before stirring; if it is extremely thin you can stir it into the paint and then strain the paint through fine muslin or mesh.

Slow drying top

    Sometimes paint (particularly oil-based paint) will take a few weeks to dry or even remain permanently tacky. This indicates that you applied the paint over a dirty or greasy surface, used an unsuitable thinner or did not stir the paint sufficiently before or during its application.

Prevention

    Thoroughly clean and prepare your surface paying particular attention to skirting which can collect a build-up of polish from the floor. Always stir the paint before and during application (except non-drip paint).

Remedy

    If the room is badly ventilated open the windows for a few days to see if this accelerates drying. If not, you will have to strip off all the paint with thinners and start again or refer to the manufacturer for advice.