Learn how to plaster...
Learn how to plaster (Stage 4)
Trowel up plaster. 'Trowelling up' means to 'work' plaster that has already been applied.
Aim– fill in all holes. The plaster is pliable enough to push into holes and hollow areas, but not too wet so as to create them. When the next stage is carried out the plaster will be very firm and it will be difficult to push plaster around and fill any holes – so ensure all are filled at this stage.
How – the plaster should be tacky – if it is too wet the plaster will be easily pushed out of shape and so creating more holes.
How– Firm pressure will push plaster along the whole length of your trowel into the holes and hollow areas. You may notice ridges caused by the trowel get worse when doing this but that is not a problem as these will be pushed out in the next stage when the plaster is a little firmer.
You cannot push too hard when doing this – as long as you have the correct angle of your trowel. If you have the leading edge any further away from the wall than 10 or 15 mm then you risk scraping. You should be able to run your trowel over the wall and push the plaster around to flatten. If when you run your trowel over the wall it starts to gather plaster then all you are doing is scraping the second coat off, so flatten your trowel into the wall.
To fill the hollows you want to push plaster in to them - not scrape plaster of the surrounding area to the level of the hollow.
If you have been over an area 3 times and the hole is still visible then more plaster should be applied in to hole and then flattened with your trowel stroke. Your trowel strokes should always be long to avoid making lots of trowel marks everywhere. As your trowel passes over each area of the walls it should be studied for holes. Be thorough and do not move on until they have been rectified.
If you are concerned the plaster is getting too firm then move quickly across the wall ensuring all large holes are filled. Then repeat stage 4 again for the smaller holes. If when you are doing this you realise there are a lot of holes then sometimes it can be quicker to go back to stage 3 and put another coat over the wall.
The corners can also be formed by scraping off the plaster from the wall you are skimming up to simply by scraping off with the tip of trowel. Do ensure all plaster is removed right into the corner. Try not to cut into the skim you have just applied on the main wall. Once the corner is free from excess plaster the corner can be formed with a brush. A paint brush (approx 75mm) will do the job. Wet the brush then flick off excess water. Ensuring the brush is pointed more at the wall you are skimming up to, run the brush in big strokes up and down the corner. Generally at this stage the plaster can be quite wet so little pressure is required. Any brush marks left in the corner can be lightly trowelled out – but again if it is really wet it may be better to leave until the next stage.
Learn how to plaster - All Stages of Skimming.