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 bricks?
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 Trade Alkali Resisting Primer prior to applying any solvent-based finishes. Alternatively, specify a Dulux Trade Quick Drying water-based paint.
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.
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.
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.
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
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.
My paint film is showing heavy brushmarks 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.
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
My plywood soffits looked great when I stained them with Cetol HLS plus a few months ago, now they look as though they've gone mouldy. What has happened?
The white deposits found on the plywood surfaces are sodium salts which originate from within the glueline of the plywood.
During the board manufacture, caustic soda is added to the glue mix to render the adhesive more soluble in water. Once the glue is cured, the caustic soda becomes superfluous. Under the influence of atmospheric moisture, it can migrate to the plywood surface and appears as a white crystalline powder. In the normal course of events, the action of rainwater washes these salts away and they are rarely visible. However, in sheltered areas, such as soffits, the salts are not removed by rain action and remain as a "bloom" on the surface.
The remedy for this is to wash down the affected areas with clean water and a bristle brush (not metallic bristles), thereby removing the salts. Provided that the finish is not damaged by over-vigorous scrubbing it need not be re-treated. It may, at some time in the future, reoccur to a lesser extent before the salts are fully depleted. Again, removal is by washing. This phenomenon seems to vary with the type of plywood and country of origin. It should be pointed out that the loss of these salts in no way affects the strength or integrity of the plywood and does not blister or crack the finish.