Wall cold joints are where one day of work ends and the next day begins. They are usually vertical in walls. They require attention at the end of each day. Keep mechanically pumped application precise so no mess is made where tomorrow's work will begin. This is why it is wise to consider larger crews and hand application for walls; the cost is equal. Supervision and clean-up are less stressful with hand applied plaster. Horizontal cold joint have been used successfully for ferrocement pillars with no separation cracks visible after 40 years, in an earthquake prone region.
Surface finish is represented as darkest grey, it stops about 2 -6 inches from the cold joint, (five to fifteen centimeters) ±. The surface finish is about 1/2 - 3/4 centimeter thick (3/16 - 3/8" ±), it is complete and ready for color.
Place a wooden trowel across the vertical cold joint. Use a horizontal motion to make the line between each day's work disappear. Pebbles can be an irritation because they roll on the hard underneath layer, wipe them away using a clean sponge. The completed cold joint is fresh plaster extending across 5 to 15 centimeters of yesterday's work, which has cured only 1 day of 28 and will bond to the new.
Be sure no excess water will create a barrier between yesterday's work and fresh mortar. If a high spot protrudes from fresh plaster, use a stone mason's chisel to carve it off.