![]() ![]() It can also include too much drying between trowel passes, hard troweling, and overworking the finish. This can happen when plastering on dry, hot days, during low humidity, in wind, etc. ![]() If the surface becomes too dry, with a dry crust on the surface but a wet paste underneath, a weakened zone can be formed just subsurface. The opposite problem of forcing too much water into the hydrating surface is allowing the surface to dry too fast. Finishers learn to time the troweling passes so that bleed water is evaporated, and the surface workable. If troweling is performed when bleed water is present, forcing bleed back into the plaster paste causes excessively high water/cement ratios in the surface finish, weakening it. One of the arts or skills of the plastering trade is properly timing the troweling passes. Swimming pool plaster is commonly troweled in three to five separate passes, the early passes placing the material where it needs to go and consolidating it, and final passes creating the smooth, final surface. Bleed water then evaporates from the surface. This process is called bleeding, and the rising water is referred to as bleed water. ![]() What happens to the excess water? As the solids (sand and hydrated, crystallized cement grains) settle, the excess water rises to the surface. This is done because if the mixture is too dry and thick, it is almost impossible to place and trowel to a smooth finish. When cement, sand, and water are mixed to form pool plaster, about twice as much water is added as is really needed to hydrate all of the cement. ![]()
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