Geology, Palaeontology & Archaeology / Re: What has caused this stripey pattern on of the wall of this building?« on: 02/12/2015 12:33:01 »
Some kinda fungus or algae from plants and the atmosphere also looks humid to so have a peace of it and take it to chemist or biologist
Stucco and other forms of plaster contain lime; CaO, as one of the main ingredients. Lime, is often used on lawns to lower the pH of the soil, since it is alkaline or has high pH. If the plaster is not mixed properly, such as not enough water or too much lime, then the finished stucco will be hot; high pH. The unreacted lime will also leach out over time, after the surface gets wet and dries during rain cycles. The answer could be one bad batch of plaster under the overhang.
Another possibility is the White House in the USA is white because the siding was lime washed. In this process, they will mix a slurry of water and lime, and this will be painted onto the surface to give a white color. If that was the case, under the overhang will not dry the same way as outside the overhang. The striping could also be an artifact of how it was applied, since the lime wash is thick. In painting terms he did not keep a wet edge, but had double coat overlap. Often the apprentice plasterer would be given a small job like, with the larger expanses left for the experts.
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