Sand-cement plaster is used extensively in building work for both protecting and decorating concrete, masonry and concrete ceilings. A good plastering technique is important for a neat, long-lasting finish.
Your tools:
• Plaster hawk
• Plaster trowel
• Wooden or aluminium straight edge
• Water bucket
• Bristle brush
Mixing plaster
1. Remove any lumps, stones or foreign objects from the sand.
2. Measure out the sand and place it in a long, thin heap on a flat, clean, hard surface (or mix in a wheelbarrow if making a small batch).
3. Pour out the cement on top of the sand.
4. Mix the cement and sand together until uniform in colour.
5. Create a hollow in the centre and slowly add clean water while mixing. The mix is correct when it is like a thick paste, able to stand by itself without collapsing, yet wet enough to be spread easily with a trowel.
Applying plaster
1. Try to avoid working in the direct sun or in drying winds, as plaster needs to retain its moisture for as long as possible.
2. Load your hawk with plaster mix and scoop onto the steel trowel. Apply to the wall with pressure.
3. Plaster small areas at a time. An entire wall should be completed in one operation.
4. Once the plaster starts to stiffen, level the surface by pulling a wooden or aluminium straight edge tool over the plaster with a swaying motion.
5. Wet the levelled plaster with water (flicked off a brush), then use a wooden float to smooth the surface.
6. Cover the plastered area with plastic or a fine spray of water to keep it damp for as long as possible. (i.e. up to 7 days).
Mix only as much plaster as you can use in 2 hours. Should your mix stiffen slightly in this period, some water may be added to regain workability. After 2 hours, the unused plaster should be discarded. Never try to retemper by mixing in additional water, as this reduces the resultant strength of the mix.
