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[edit] Applying The Floating Coat
Before the plaster is mixed the wall should be thoroughly doused with water using a distemper brush. This helps the plaster to adhere more easily as well as cutting the suction on surfaces such as old plaster.
Always add the plaster powder to the exact amount of water held in a plastic bucket, if you try to add water to the powder the result will be a lumpy mixture. Stir it vigorously until it reaches a thick workable consistency rather like whipped cream.
Once the plaster is thoroughly prepared, transfer all of it carefully to the spot board (the mixing platform) and wash the bucket thoroughly before progressing. Then transfer about one third of the quantity you have mixed onto the hawk by scraping it over the edge of the spot board with the laying on trowel.
Whilst working on the wall, try to keep the trowel clean of unwanted plaster by constantly raking it against the edge of the hawk. Lumpy plaster, sticking to the trowel, is easily removed by dipping it occasionally into a bucket of clean water.
To be useful the plaster needs to be transferred in manageable amounts from the hawk onto the trowel. To do this, stand near the wall, tilt the hawk upwards and scrape a small pat of plaster onto the trowel, holding the blade horizontally so that the load is carefully balanced on top.
When applying the plaster to the wall start near the center of each bay and work out towards the edges. Use the blade of the trowel to push each pat of plaster hard against the wall and draw the trowel upwards in a wide sweep to flatten it. If you keep the blade of the trowel almost parallel to the wall, with its top edge tilted slightly outwards, the plaster will be fed onto the wall as the trowel moves (fig. 7).
Slowly build up the layers of plaster until the material is level with the top edges of the battening. Try to finish off one bay at a time and then, while the plaster is still wet, level the surface by placing a straightedge across the face of the battens. By sliding the straightedge across the plaster, you should be able to remove excess material as well as spotting low areas which need more (fig. 8). If small inconsistencies remain after this has been done, or appear while the plaster is drying, they should be flattened out with a skimming float.
After the whole wall has been plastered, the setting out boards can be removed. This is most easily done when the plaster is semi dry after about one hour, but take care even then that no material is pulled away as the battens are removed. Once the floating coat dries completely fill these gaps with fresh plaster up to the level of the surrounding material (fig. 11).
[edit] Applying The Skimming Coat
The final skimming coat is applied directly on top of the floating coat without the use of any setting out boards as guides. If the first coat of plaster has been applied correctly, it only needs the addition of a topcoat a few millimetres thick to give a perfect level finish.
Begin by wetting the wall thoroughly using clean water and a distemper brush to aid adhesion.
Mix the finishing plaster to a creamy consistency in a clean plastic bucket and transfer this onto the spot board. Scrape about a third of the quantity you have prepared onto the hawk so that it can be applied to the wall more easily using the laying on trowel. The plaster should be applied very thinly (3mm at most) using firm upward strokes of the laying on trowel to scrape it onto the wall. Try to cover as wide an area as possible in bold sweeps (fig. 13) and gradually fuse these together to cover the wall.
As the plaster is applied, wet the laying on trowel constantly and run it over the surface in a circular polishing movement (fig. 14).
If you are finishing a large wall you will find it difficult to complete the whole area in one go because the plaster sets too fast before it can be finished off with the trowel. To avoid this, work in sections, lightly sanding away the overlapping lines.
[edit] Problems To Watch Out For
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