Try a paste of hydrogen peroxide and baking soda and let set 20 minutes. It may take multiple applications. Hydrogen peroxide turns to water after exposure to air about 20 minutes. Wiping tub/shower after each use with squeegie or chamois will tend to keep surfaces dry and minimize mineral deposits and mold/mildew. Leaving shower curtain/door open will improve ventilation into the tub/shower area. Keeping surfaces clean and dry will minimize mold/mildew as will improving bathroom ventilation. Run vent/fan for 30 minutes after bathing to help remove moisture from the air in the bathroom.

Ceramic tile is a mixture of clays and other natural materials. The special clays are mined from the earth, shaped, colored and than fired in kilns. Traditional ceramic tile can be naturally colored and left unglazed like terra cotta, or they can feature colored or highly designed surfaces which can be glazed (finished with a glass surface) either in a high gloss or matte finish. Most ceramic tile has either a white or red body coloration underneath the glazed, colored top layer. Glazed porcelain has a body made of the porcelain material and then a glaze is applied over the surface much like a regular ceramic tile Porcelain tile is a newer form of ceramic tile and extremly popular among homeowners. Porcelain tiles are composed of fine porcelain clays and fired at much higher temperatures than ceramic tiles. This process makes porcelain tile more dense, less porous, much harder and less prone to moisture and stain absorption than ceramic tiles. For these reasons, most porcelain tiles are suitable for both indoor and outdoor installations. Porcelain tiles are also harder to cut due to their density and hardness. For other information you can check this site Ciciliot

gigabit: thanks. I was WAY off on what I thought it meant. I read your link. I was thinking I wanted colorthrough porcelain, unglazed, for the same color all the way through, so when you drop a cast iron frying pan on it, the chip is the same color. (Which I have done!) But I've had my glazed ceramic tile floors throughout this house for 10 years now, and only that one chip in the kitchen. So, this is not a major problem. For the new house, maybe I should consider the same tiles again. My only concern is these floors are a bit slippery for us, and we're getting older. I'll have to see if there are any glazed ceramic that have a higher COF (I think that's what you call it.)

There is some helpful information about Sintered Stone vs Porcelain here: https://www.tenax4you.com/compact-surfaces-sintered-stone-porcelain-compared-s/2092.htm That website has several articles making comparisons between different materials. Might be a page to bookmark and share with others since the properties of natural stone, engineered stone, and other man made materials can get pretty confusing sometimes. Hope the information helps future readers.