Polyethylene film and other plastic sheet materials are available in clear, white, or black and are easily handled; the white is especially good for covering fresh concrete subject to sunlight.These films avoid leaving a residue that can prevent the bond of new concrete to hardened concrete or the bond of resilient floor coverings to concrete.Plastic films are particularly effective for curing the base slab of two-course floors.They can, however, leave blotchy spots on the slab and should not be used for coloured concrete or where the appearance of the slab surface is important.The sheets should be spread as soon as possible after finishing operations without marring the surface finish.Edges of sheets should be lapped a sufficient distance to prevent moisture loss and sealed with tape, mastic or glue, or held in place with wood planks or sand.Construction traffic should be restricted because the film can be extremely slipperyThe water-Proof paper has the same advantages and disadvantages as plastic film, except that discoloration is less likely.It should be light in colour; the edges should be lapped and sealed and left in place for the duration of the curing period.Tears caused by construction traffic should be repaired to maintain proper moisture retention.