As you can see from the Moh Hardness Scale above that Spot-X Glass Restorer is at level 5 and Glass is at a harder level of 5.5, this means that anything that is below that hardness will be removed from the glass without scratching the glass. Also this scale shows that Spot-X can be used on other materials that are harder than glass without scratching or dulling the surface. Please be aware that Chrome must be good triple plate and Marble (not shown) must be Serpentine Marble otherwise these surfaces might retain scratches. It is recommended that a small inconspicuous area be tested first. Spot-X is softer than glass, it will not scratch, but its harder than the mineral, calcium and salt stains that it rips right through!