WONDERSKIM™ is a Ready to Use Troweling Filler and the easy way to fill Cracks and give a perfectly Smooth, Weatherproof Finish to Rough or Uneven Plaster and other Building Substrates like Gypsum and Composition Boards. WONDERSKIM™ it on and smooth it off – it will set hard in about 24 hours to a finish that is both weatherproof and alkali resistant. It is best to prime with Classiseal Multipurpose Primer™. WONDERSKIM™ can be tinted with small amounts of universal colourants, or PVA paints, to match existing surfaces, and improve the colour uniformity of topcoats – developed to last in Coastal areas as well!


If standard preparation and standard application procedures are followed, an outstanding smooth finish can be obtained.

  • For exterior and interior use;

  • Can be applied to damp surfaces;

  • Resists mould and fungus growth;

  • Raw or previously Painted Surfaces;

  • Skims up to 5mm thick without sagging;

  • Ideal for filling small holes and hairline cracks;

  • Water based, therefore all equipment can be cleaned with water;

  • Non-toxic and non-irritant if standard painting conditions and code of painting practice is adhered to.


TYPE  -  Modified Acrylic Emulsion;
SKIMMING THICKNESS  -  Maximum 3-5mm;
DRYING TIME  -  Surface: 1-2 hours (at 23° Celsius and 50% Relative Humidity);
HARD DRY  -  Single Coat - 24 hours (at 23° Celsius and 50% Relative Humidity);
OVERCOATING  -  24 Hours;
VISCOSITY  -  135 - 160 KU - Paste;
THINNING  -  None required except tap water to adjust consistency in extreme cases;
DENSITY  -  Approximately 1.69kg / Litre;
SPREADING RATE  -  From 2m²/litre down to 0.2m²/litre – varies with thickness being applied;
FLASH POINT  -  Not applicable;
VOLUME SOLIDS  -  41 - 43% (100u wet film will give 42u dry film);
COVERAGE (THEORETICAL)  -  1 - 4m² per litre for entire application system;
FLASH POINT  -  Not applicable;
COLOUR RANGE  -  White Only;
PACKING SIZE  -  1 Litres, 5 Litres, 10 Litres and 20 Litres.


  • Spreading = ± 2m²/Litre depending on thickness;

  • Cracks or holes deeper than 5mm must be filled with the appropriate Plaster Filler;

  • Previously painted surfaces must be sanded to a flat finish before applying Wonderskim™;

  • Ensure all surfaces are clean before application:

  • Surfaces must be clean and dry. Remove all loose plaster, dust, old paint and wallpaper by brushing with a stiff wire brush. If necessary wash with Classic Sugar Soap;

  • Narrow cracks are best to be widened with a sharp tool to ensure effective filling;

  • Apply only as much WONDERSKIM™ as needed, it is advisable to build the film thickness in multiple layers rather than one thick coat (maximum thickness;

  • Allow to dry for at least 2 hours before sanding with 100 grit sand paper to a smooth finish. Thick applications or damp weather may require a slightly longer drying period;

  • Always use clean utensils, and ensure the mixing vessel or surface has no residues of old, mixed crack filler;

  • Remove excess product from tools before cleaning in warm water. For best results add Classic Sugar Soap;

  • Do not store in extreme temperatures, and never allow freezing. To prolong shelf life, replace plastic liner and lid to stop product drying out when storing, and store in a cool, dry place.


WONDERSKIM™ can be applied with a steel trowel or a paint scraper / spatula, by pressing firmly against the substrate and scraping the surface in an upward sweeping action, maintaining a firm and even pressure. Apply only as much Wonderskim™ as needed, it is advisable to build the film thickness in multiple layers rather than one thick coat (maximum thickness 5mm). Sponge down with damp sponge to eliminate sanding.


  • The ambient temperature must be between 5ºC and 35ºC and humidity between 10% and 85%;

  • Care must be taken when applying finish coats in low temperatures and an allowance made for slightly longer setting and drying times. WONDERSKIM™ must only be applied where backgrounds are not frozen or will remain at 5°C or above until dry;

  • Do not paint too early as the wall may still be damp - paint only when the walls are dry;

  • Do not paint in too hot weather, rather paint early morning and after lunch, the slower the WONDERSKIM™ dries, the longer it lasts;

  • Excessive application thickness and/or rapid drying could lead to cracking;

  • Avoid applying under adverse weather conditions as this could result in poor product performance;

  • Excessively friable surfaces should be cleaned down prior to primer application.


Painting is a relatively user-friendly activity if the proper precautions are taken to ensure safety;

  • It is advisable to wear gloves as WONDERSKIM™ is difficult to remove from skin;

  • Always keep out of reach of children and animals;

  • Do not take in orally - harmful if swallowed. Seek medical attention and do not induce vomiting;

  • If accidental contact with skin, wash immediately with soap and water or a good quality skin cleaner;

  • If accidental contact with eyes, rinse immediately with plenty of water and seek medical advice;

  • Wear a respirator if the area being painted cannot be adequately ventilated, and work for short periods only;

  • Ventilate the area to be painted, opening all doors and windows and using fans during application and drying;

  • Protect floors with cloth Drop Cloths, not plastic, which is far more slippery;

  • Do not paint or store paint near any heat source such as a water heater or fireplace, and never smoke while painting;

  • Make sure your ladder is in good shape. Set the legs on an even surface and lock the cross braces. Do not stand on the top of the ladder nor on the utility shelf. If you are having difficulty reaching a spot, get down from the ladder and move it rather than leaning out;

  • Clean up carefully and thoroughly when you are done for the day;

  • If rags have alkyd paint or thinner on them, leave them to dry outside to avoid any chance of spontaneous combustion;

  • Choose an area inaccessible to children and pets, and when they are thoroughly dry, take them to a toxic-waste dump site.


Different surfaces and environmental conditions require specific painting systems to produce the best possible results - It is, therefore, recommended that you contact a representative from Classic Paints for advice on all your painting requirements, whenever possible.

The information, and, in particular, the recommendations relating to the application and end-use of Classic Paints products, are given in good faith based on Classic Paints’ current knowledge and experience of the products when properly stored, handled and applied under normal conditions. In practice, the differences in materials, substrates and actual site conditions are such that no warranty in respect of merchantability or of fitness for a particular purpose, nor any liability arising out of any legal relationship whatsoever, can be inferred either from this information, or from any written recommendations, or from any other advice offered. The proprietary rights of third parties must be observed. All orders are accepted subject to our current terms of sale and delivery. Users must always refer to the most recent issue of the Product Data Sheet for the product concerned, copies of which will be supplied on request.


26/05/2022 - This supersedes all previous publications - This technical data furnished is obtained from controlled laboratory tests under ideal application conditions. No guarantee of any performance characteristic is given or implied and we do not hold ourselves responsible for any consequential damage of whatsoever nature that may arise from use of our products. In the event of a proven product fault our liability will be limited to the replacement of the product only. It is the user’s responsibility to confirm the currency of product data sheets.

Download as Pdf Document