Averages are for Corvallis Municipal, which is 5 miles from Corvallis.
Warnings. Do not use pumice stones to clean marble, laminate, plastic or fiberglass toilets; doing so will result in permanent scratches. A dry pumice stone will also scratch porcelain, so be sure to keep the stone and the toilet surface wet at all times.lean With a Pumice Stone. Before cleaning a porcelain toilet with a pumice stone, you must thoroughly wet both the stone and the surface to be cleaned and keep the stone and the surface wet as you work.
Sweep the slate with a broom to remove any loose dust or soot. Dissolve 1 cup of washing soda (sodium carbonate) into 2 cups of boiling water. Mix well and add in 1/2 cup powdered pumice and 1/2 cup ammonia. Brush this mixture onto the slate and let it sit for 30 minutes.