DEFECTS AND SOLUTIONS (Back to top)
| Q. |
Bittiness |
| A. |
Take the utmost care during both preparation and application. Ensure surfaces are smooth. Strain the paint if necessary. Avoid dusty conditions and use clean equipment. |
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| Q. |
Bleeding |
| A. |
If possible, strip off the old paint. If this is impractical, seal the surface with Patent Knotting or Johnstone's Aluminium Wood Primer. |
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| Q. |
Blistering |
| A. |
Ensure that the paint adheres effectively to the surface. Remove all defective paint. Let each coat fully harden before further application. |
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| Q. |
Brush marks |
| A. |
Keep paint to a moderately thin consistency and brush out to a thin even coating. Cross brush and lay-off with very light strokes. |
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| Q. |
Cissing |
| A. |
Occurs with poor adhesion when an old previously painted surface hasn't been rubbed down or is so hard that it is impervious to the new coat. Seen as small depressions or holes in the paint surface.
Try vigorous brushing. If this doesn't work, wash off new paint and rub down with White Spirit. II the new surface has dried, rub down and re-finish. |
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| Q. |
Curtaining, Running or Sagging |
| A. |
Brush out well, cross brushing and laying off evenly. If the defect has occurred in old work, rub down thoroughly before re-painting. |
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| Q. |
Discolouration |
| A. |
There no effective treatment other than repainting. |
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| Q. |
Efflorescence |
| A. |
Seen as white furry crystalline deposits on new plaster and cement. Ocurrs as the surface dries out.
Do not seal. Use only an emulsion paint. Remove by dry brushing from time to time. |
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| Q. |
Fattening and Feeding |
| A. |
Do not mix different brands of paint. Where thickening is slight the problem can be rectified by use of thinners. |
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| Q. |
Flaking |
| A. |
Solvent-borne finishes: Remove all paint and start again.
Water-borne finishes: Scrape off all loose paint and seal with a solvent-borne primer. |
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| Q. |
Flashing or Sheariness |
| A. |
Glossy streaks or patchiness observed when viewing a surface from a shallow angle.
Thin paint to ease brushing. Use a roller or apply paint quickly. Do not touch after "initial set". |
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| Q. |
Grinning |
| A. |
Seen where previous undercoat shines through.
Use recommended undercoats. Avoid over thinning of the top coat. |
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| Q. |
Loss of Gloss |
| A. |
Allow the surface to harden. Rub down and repaint. |
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| Q. |
Mould and Mildew |
| A. |
Ask your local Johnstone's outlet for advice on the particular location in which the problem is occurring. |
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| Q. |
Saponification |
| A. |
Occurs when solvent-borne paints are affected by alkalis in the presence of moisture.
Prevent by using Johnstone's Alkali Resisting Primer. Where saponification has already occurred, strip, wash, allow to dry and re-paint. |
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| Q. |
Wrinkling |
| A. |
If the paint is sufficiently hard, rub down and repaint. If the film is still very soft scrape off the gloss coat, clean with White Spirit and re-paint. |
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| Q. |
Fibre insulating boards |
| A. |
Fibre insulating boards may be pre-treated with fire retardant chemicals. If treated, prime with Johnstone's Alkali Resisting Primer. Where a solvent-borne finishing system is required, prime with Johnstone's Alkali Resisting Primer or Johnstone's Joncryl Acrylic Primer Undercoat. In areas of condensation it may be necessary to paint the back of fibre insulating boards to minimise the risk of warping. Untreated boards can be painted with water-borne paints such as Johnstone's Covaplus Vinyl Matt Emulsion without the use of a primer. |
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SURFACE PREPARATION AND PRIMING (Back to top)
| Q. |
How to prepare surfaces for painting |
| A. |
The importance of preparation of the surface prior to painting cannot be over emphasised. No surface should be painted unless it is in a sound, firm, clean, dry condition and completely free from dirt, dust, oil, grease, rust and efflorescence. All loose and flaking materials should be removed by scraping, wire-brushing or other suitable methods, Normally dirty surfaces can be adequately cleaned with water and soap, or detergent. Heavy deposits of grease or fat can be removed b swabbing with sugar soap. Previously painted surfaces should be rubbed down to provide a suitable "key" for subsequent coats of paint Usually rubbing down is best carried out using wet and dry abrasive paper and water. This helps to avoid scratching the surface, and prevents dust from flying about. When dry sanding, wear a suitable dust mask. Surface imperfections such as holes, cracks and dents should be made good with a suitable filler. |
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WOOD (Back to top)
| Q. |
Unpainted Softwood |
| A. |
Ensure the wood is dry and free from oil, grease or other contaminants and dust off thoroughly. Apply a knotting solution to all knots and resinous areas, coating sufficiently beyond the defect to ensure efficient sealing. Liberally apply a suitable primer and brush well into the surface. Ensure the final coat is smooth and even. |
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| Q. |
Previously painted softwood |
| A. |
Remove all defective paintwork, either by using a heat gun or use of paint remover. Ensure all traces of paint remover are thoroughly cleaned off. Rub down with fine waterproof abrasive paper and rinse thoroughly. Apply knotting solution and prime bare areas as for unpainted softwood. |
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| Q. |
Suggested primers for softwood |
| A. |
Johnstone's Wood Primer, Johnstone's Joncryl Acrylic Primer Undercoat, Johnstone's Aluminium Wood Primer (particularly suitable for resinous timber). |
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| Q. |
Unpainted hardwood |
| A. |
Ensure that wood is dry and free from oil, grease and any other contamination. If any delay occurs between preparation and priming, it is a sensible precaution to wipe over the surface with White Spirit, due to the oily nature of some hardwoods. Dispose of cloths contaminated with White Spirit safely. Liberally apply a suitable primer. Ensure the final coat is smooth and even. |
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| Q. |
Previously painted hardwood |
| A. |
Spot prime all open joints or other defects of the remaining paintwork. When dry, stop with a suitable hard stopper to prevent water penetration. Wash all remaining painted surfaces with water and detergent to remove any contamination. Rub down with fine waterproof abrasive paper and rinse thoroughly. |
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| Q. |
Wood treated with creosote |
| A. |
Painting over creosote is not recommended unless the creosote is well weathered. Prepare the surface ensuring it is dry and free from grease etc. As discolouration or "bleeding" is likely to occur, normal paint systems cannot be used. The surface should be sealed with Johnstone's Aluminium Wood Primer, or Johnstone's Quick Dry Primer Sealer. A second coat of Primer should be applied if the first coat discolours. Certain Johnstone's Woodcare products such as Exterior Shed & Fence Treatment can be applied direct to weathered creosoted timber. |
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| Q. |
Suggested primers for hardwood |
| A. |
Johnstone's Wood Primer (non-oily hardwood), Johnstone's Aluminium Wood Primer. |
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| Q. |
Microporous systems |
| A. |
Timber to be over-coated with a microporous system such as Johnstone's Stormshield Flexible Gloss, Exterior Satin Finish Woodstain or Opaque Wood Finish, should be given a pre-coat of Johnstone's Woodworks Universal Primer before applying the correct system as directed. |
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PLASTER & MASONRY (Back to top)
| Q. |
Plaster |
| A. |
Remove any surface contamination and make good any cracks with an appropriate filler. Remove efflorescence by dry brushing as it appears and until it ceases. In order that effective drying takes place, ensure good ventilation. Normally priming should be carried out using a permeable emulsion paint. Johnstone's Jonmat Obliterating Matt Emulsion is recommended in this instance. If a final coat of Professional Gloss, Eggshell Lustre or other solvent-borne finish is required, prime with one coat of Johnstone's Alkali Resisting Primer applied to the dry substrate. Liberal application of the primer is recommended to compensate for varying degrees of absorbency in the plaster. |
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| Q. |
Concrete, brickwork, cement rendering, masonry |
| A. |
Thoroughly brush down with a stiff brush to remove any dust or surface contamination. Repair defects and cracks with the appropriate materials. On porous or friable surfaces apply one coat of Johnstone's Stormshield Stabilising Solution or Johnstone's Stormshield Quick Dry Stabilising Solution or if the surface is very sound, apply finishing coats of the required coating direct. If finishing with a solvent-borne system, first prime with Johnstone's Alkali Resisting Primer. Johnstone's Stormshield Pliolite Based Masonry Finish is self-stabilising and can be applied direct to the substrate as directed. |
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| Q. |
Previously painted plaster, concrete, brickwork, cement rendering, masonry |
| A. |
Repair all cracks and defects with a suitable filler. Wash down the remaining areas to remove dirt etc. Rub down previously gloss painted surfaces with waterproof abrasive paper to provide a "key" for subsequent coats, rinse with clean water and allow to dry. Prime any bare areas as suggested for the particular substrate. |
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| Q. |
Fletton common bricks |
| A. |
Paint adhesion problems can occur on this type of external brick. The presence of kiss marks, dark, smooth and sometimes slightly glazed areas can result in paint failures in less than two years. In addition a tendency to form powdery surface deposits of efflorescence can also cause subsequent failure. All paint types are affected and thick films can fail extensively due to the added effect of trapped moisture. External rendering, carried out in accordance with BS5262, can provide satisfactory adhesion for paint systems. Sand-faced and rustic Flettons can be painted satisfactorily. |
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BUILDING BOARDS (Back to top)
| Q. |
Cementious boards and sheets |
| A. |
Observe the requirements of the current regulations and best practice codes before carrying out any work. Owing to the alkaline nature of cement, priming with Johnstone's Alkali Resisting Primer is necessary if a solvent-borne coating system is to be applied. Priming may not be necessary if water-borne products are to be used. Where condensation is likely to occur in cavities or roof spaces, it is advisable to prime the backs of boards or sheets. In very wet environments it may be necessary to use non-saponifiable paints such as Johnstone's Stormshield Pliolite Based Masonry Finish. |
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| Q. |
Plasterboard and other paper-faced boards |
| A. |
Plasterboard is extensively used in dry lining systems and jointing compounds, paint treatments etc should be as per manufacturer recommendations. Paper faced compressed straw slabs and wood based boards etc do not normally present painting problems. |
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| Q. |
Fibre hardboards |
| A. |
Hardboard does not provide any problems in painting. The surface does not need to be rubbed down but should be clean and free from grease. Prime as for untreated fibre insulating boards. |
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| Q. |
Polystyrene sheets and tiles |
| A. |
The manufacturer's painting recommendations should be followed. Clean off any dust and apply any Johnstone's water-borne paint product. On no account should solvent-borne products be used. |
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METAL (Back to top)
| Q. |
Galvanised iron and steel |
| A. |
New galvanised surfaces are usually very smooth, making firm adhesion of paint difficult. If they are allowed to weather for some weeks this effectively etches the surface providing a more suitable substrate for painting. As it is sometimes necessary to apply primer direct to unweathered galvanised surfaces, care should be taken to remove all traces of oil and grease etc. Degreasing with White Spirit using clean cloths, is often very effective. Follow by thoroughly washing with detergent and water, rinse well and allow to dry. Dispose of cloths contaminated with White Spirit safely. |
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| Q. |
New galvanised iron and steel |
| A. |
Completely remove any oil or grease, etc. Apply a liberal coat of Johnstone's Mordant Solution allowing the solution to darken the metal. Wash off any surplus solution, allow to dry, then prime with Johnstone's Universal Primer or a suitable primer from the Johnstone's Performance Coatings range. |
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| Q. |
Weathered galvanised iron and steel |
| A. |
Clean the surface to remove all traces of oil, grease and any other contamination. Remove any rust back to bare metal and treat with Johnstone's Mordant Solution as required. When dry, prime immediately with Johnstone's Universal Primer or a suitable primer from the Johnstone's Performance Coatings range. |
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| Q. |
Iron and steel |
| A. |
Iron and steel require very thorough surface preparation and protection with a suitable and effective paint system. Poor preparation results in ineffective paint protection. The most effective preparatory methods for cleaning iron and steel are shot blasting, grit blasting, flame cleaning, impact needles and some forms of chemical cleaning. Hand cleaning methods are generally less effective and any scraping or wire brushing must be as thorough as possible. It is imperative that there should be no delay before priming clean iron and steel as exposure to the air can cause surface deterioration in a very short time. Priming within one hour of preparation is advised. |
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| Q. |
New or unpainted iron and steel |
| A. |
Remove all oil, grease, by solvent cleaning methods. Remove any rust or millscale by the most effective means to produce a surface suitable for painting. Ensure the surface is dry and apply a coat of suitable primer, brushing well into the grooves and applying liberally to angles and edges. Recommended primers are Johnstone's Universal Primer or any suitable primer from the Johnstone's Performance Coatings range. |
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| Q. |
Previously painted iron and steel |
| A. |
If the whole surface is in a poor condition, remove existing paint with a proprietary paint remover and prepare as for unpainted iron and steel. Generally sound paintwork should be checked for any loose or flaking material, which should be removed down to bright metal. Prime all bare metal immediately with Johnstone's Universal Primer or a suitable primer from the Johnstone's Performance Coatings range and allow to dry. Thoroughly degrease remaining areas prior to the application of any further coating. |
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| Q. |
Pre-primed iron and steel |
| A. |
Ensure that the primer has been correctly and effectively applied to the surface. Rectify any surface defects by cleaning and spot priming. If the surface has not been properly primed, or millscale and rust are present, remove by the most effective means and treat the surface as for unpainted iron and steel. |
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| Q. |
Bitumen coated iron and steel |
| A. |
New bitumen or bituminous materials should not be painted except with further coats of bitumen, owing to the risk of bleeding or surface cracking. It may be possible to paint hard or weathered bituminous coatings provided a suitable sealer, e.g. Johnstone's Aluminium Wood Primer is applied to reduce the risk of bleeding. Ensure all surfaces are clean and dry and that any bare areas have been spot primed with a suitable primer. |
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| Q. |
Non-ferrous metals: copper, brass and similar alloys |
| A. |
These metals are difficult to paint as no effective key is provided for paint adhesion. They are best left unpainted. If painting is essential, lightly abrade the surface with waterproof abrasive paper and clean down with White Spirit. Dispose of cloths contaminated with White Spirit safely. Prime with Johnstone's Universal Primer or a suitable primer from the Johnstone's Performance Coatings range. |
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| Q. |
Non-ferrous metals: aluminium and aluminium alloys |
| A. |
Aluminium has a smooth even surface, containing a white oxide layer; it is therefore necessary to prepare the surface to provide a sufficient key. Aluminium should always be kept from contact with any caustic solutions or substances. Prepare bare metal by lightly abrading with waterproof abrasive paper using White Spirit as a lubricant. Clean down with White Spirit and dry thoroughly. Dispose of cloths contaminated with White Spirit safely. Prime with Johnstone's Universal Primer or a suitable primer from the Johnstone's Performance Coatings range. |
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| Q. |
Previously painted non-ferrous metals |
| A. |
Remove all flaking and badly adhering paint; if necessary remove using paint remover and treat as for a new surface. If surface coatings are sound, clean down with White Spirit, wash with detergent and water and thoroughly rinse with clean water. Dispose of cloths contaminated with White Spirit safely. Spot prime any bare areas as indicated above. |
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DIFFICULT & UNSOUND SURFACES (Back to top)
| Q. |
Non washable distempers |
| A. |
These should be completely removed by repeated washing. Allow the surface to thoroughly dry and apply one coat of Johnstone's Alkali Resisting Primer. |
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| Q. |
Cement paints and limewash |
| A. |
These materials should be completely removed prior to painting. Alternatively a thorough brushing clown with a stiff bristle brush followed by 1 or 2 coats of Johnstone's Stormshield Stabilising Solution may suffice. |
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| Q. |
Nicotine stained surfaces |
| A. |
Remove as much of the stain/smoke residue as possible with sugar soap, rinse well with clean water and allow to dry. If the surface is heavily stained apply one coat of Johnstone's Aluminium Wood Primer. It the staining is slight apply one or two coats of Johnstone's Alkali Resisting Primer. |
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