Use two coats of Dulux Trade QD Wood Primer/Undercoat and then apply one coat of Dulux Trade High Gloss. Remember primer only comes in white so extra coats of a vibrant colour may be required.
"Hot" or "hungry" surfaces should be primed overall with very thin finishing coats of emulsion or Primer Sealer prior to painting.
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.
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.
There are different solutions for each of these problems.
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.
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 Stain Block Plus prior to finishing.
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 internally with Stain Block Plus, externally with Alkali Resisting Primer.
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 a 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 Trade Weathershield Multi-Surface Fungicidal Wash. Leave for 24 hours, wash down to remove residues and allow to dry 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.
