The first thing to remember is that we use the word trowel and not polish.
Polish implies that the plaster skim is going to have a shiny finish.
The objective is to achieve a plastered skimmed wall that is flat, smooth and matt in look.
A shiny plastered wall is difficult to paint or wallpaper. The decorator will simply sand it down back to a matt finish and spend that time “calling” the plasterer!
There is a three stage process to trowelling a wall.
This three stage trowelling process used in conjunction with the pattern of three prevents the plastered wall becoming over trowelled or polished and ensures a consistent quality of finish over the plastered wall. It helps to prevent the plasterer spending too much time on one part of the wall and prevents the wall becoming too trowelled and eventually blistered.
Stage one occurs immediately after you have finished the laying down coat. It involves passing the plasterers trowel over the entire skim plastered wall, still following the pattern of three, three times. The objective of this stage is to smooth the wall, fill in any “cats’ eyes”, remove any remaining plaster lumps; tighten the corners, edges and beads. It is not necessary to pass over the wall three time if you have achieved a high quality finish in either the laying down plaster coat process or the first two of the subsequent trowels. The suggestion of three passes over the wall for stage one is to stop you over trowelling. You should not dwell on any particular area of the wall. Treat the entire wall equally. Spending too much time in one area can cause you to create a mixed quality wall. This stage one process should be completed whilst the plaster is still wet on the wall and can be moved and smoothed with ease. No water should be used in this process.
Plaster Trowelling Stage 2 should be done when the plaster is firm but still leaves a damp mark on your fingers when touched. The plasterers trowel should be wet with a brush for each passage of the trowel over the wall. The water used should be freshly drawn to prevent accelerating the hardening process of the plaster. You will pass over the wall three times following the pattern of three. Keep the plastering trowel wet to ease the passage of it over the plastered wall. Bring the plaster fat down the wall with you so as not to leave streaks on the wall. Adjust the angle and pressure of the plastering trowel in order to compress and smooth the plaster. Pay particular attention to the corners and edges at this stage. Use a damp, not wet, brush to brush in the corners to tighten and smooth them up.
Plaster trowelling Stage 3 involves wetting the wall. The wall will feel hard and dry to the touch . This stage involves wetting the wall with clean water and either a broad yet soft brush in front of each stroke of the trowel or wetting the trowel The process is identical to stage 2 other than this.
By the end of stage 3, the wall should be flat, smooth and matt. Corners and beads will be tight, smooth and clean. The job is now done.👍😀