Skimming is a term used for applying a thin coat of plaster to a wall or ceiling to provide a smooth uniform surface. The amount of plaster needed can be worked out by area/weight. 10kg should be sufficient to cover about 5 sq m at a thickness of 3mm. Only buy plaster when you need it, as the shelf life is minimal, and ensure it is kept in a dry room away from damp.1: Preparation Before starting, you should clear out the room and dust down the plasterboard. The idea is to get rid of as much dust as possible since all surfaces need to be kept clean. Dirt and dust can cause problems later and it only takes a short time to clean up. Clear the area of furniture and spread plenty of plastic sheeting over the floor. If you are plastering over new plasterboard, press scrim tape over all the board joints and screw metal reinforcing angle bead to all external corners. 2: Mixing the plaster Mix your plaster according the instructions on the bag. Always add the plaster to the water and use a clean mixing bucket. It’s essential to mix the powder and water thoroughly so that you have a thickish, creamy consistency with no lumps. A paddle accessory fitted to a corded electric drill is the best method of mixing. Plaster can set in minutes, especially in the summer, so only mix as much as you can use immediately. Don’t add new plaster to an older mix and don’t add water to the plaster to try and make it more workable. 3: Applying the base coat Scrape a trowel full of plaster off the mixing board and onto your hawk. Next, transfer half the plaster to your trowel. Keep your trowel wrist straight and use a flicking action with your ‘hawk hand’ to move the plaster from hawk to trowel. Working from the bottom of the wall, use smooth strokes to press the plaster onto the wall. Gradually narrow the gap between the trowel’s top edge and the wall as you move the tool upwards. Always keep the trowel at a slight angle to the wall at the end of the stroke. If the trowel is flattened against the surface it may pull the new plaster away from the wall. Work over the whole area aiming to apply a base coat - don’t worry about any uneven areas or holes at this stage. This coat should be around 2mm thick. Use the angle beading as a guide when plastering up to external corners. 4: Smoothing the surface Clean around the edges of the wall with a wet paintbrush to remove lumps and lines of plaster that are on the ceiling or adjacent walls. The next stage is to level and smooth the surface but this can only be done when the plaster has hardened slightly but is still pliable. This working time will vary from a few minutes in summer to twenty minutes or more in very damp cold environments. Use your trowel at a very shallow angle to the wall and work over the surface smoothing the surface. You can add a thinner skim of more plaster to fill holes and even out depressions. 5: Drying And Polishing Leave the plaster to dry once more - for around 30 to 40 minutes. Now the plaster can be polished. Wet the face of your trowel and flick water onto the wall with a large paintbrush. The idea is to provide just enough lubrication for your trowel to float over the surface and fill tiny holes and imperfections. Work in regular sweeping strokes and finish with long continuous strokes across the wall. Wash your mixing board and tools as soon as you’ve finished work. Don’t keep opened plaster bags for more than a couple of weeks.