Home improvements are messy. Though you take steps to protect your hardwood floors from sticky media like plaster, drips and spills can dry on hardwood quickly. Cleaning dried plaster off a hardwood floor is more difficult than resolving a fresh spill, but it is possible. Get to work as soon as you notice the dried plaster to keep as much of the material from becoming ground into the hardwood surface as possible.
Moisten the hardened plaster before trying to clean the accumulation from the hardwood floor. Dampen a soft white cloth with warm water and place on top of the plaster for several minutes to loosen the mixture. If the plaster stains are widespread, run a damp -- not wet -- mop over the plaster. Avoid saturating the wood floor with water to prevent warping and rotting of the wood.
Place a dry white cloth over the plaster and apply heat with a clothes iron. You can safely keep dry heat on the hardwood floor for a longer period than damp heat.
Scrape -- carefully, to avoid scratching -- the dried plaster from the hardwood with a blunt object such as a putty knife or butter knife.
Remove stubborn dried plaster with a sander. This method is more time-consuming because you also remove the floor's finish. After taking the plaster off the floor, touch up the floor with a wood finish to reseal the wood.