When use cement to adhere stone , after hygroscopic matter permeating stone  interior, causes the stone  surface to have the wet mark which is not easy natural drying, this is the popular name water stain.

1,water stain manifestation
The water stain caused because not doing the protection prevention process on the stone
the water stain caused because of the brush of the protection  not evenly.  
the water stain caused because the bottom face was not brushed with protection
the water stain caused because the side face was not brushed with protection .

2,water stain distinction
Uses the clear water moist wet mark place on stone , then with the pH widespread indicator paper measure its pH value, the indicator paper appear the blue color (pH value >7), is the alkalinity. In addition, regardless of how does the weather change, the stone  surface's wet mark always could not be dried, even use flame to bake its surface, also very difficult to dry.

3,water stain type
analyze according to the mechanism which forms the water stain, mainly has the following several types:

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