More marble is damaged by acid etching than any other single source . Acid etching is the name given to corrosion of the stone such as marble and limestone which is caused by the acid found in many common foods, drinks and cosmetic products eg juice, soft drink, lemon,wine, soap and so on. Also embedded watermarks from cups, glasses and bottles. These acid spills will etch the stone surface immediately ,weather they are impregnated sealed properly or not. Etching appears on your marble as spots or areas that are duller than the surrounding surface and sometimes slight roughness can be felt.