Naked Science Forum

Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: shoshone on 28/11/2015 09:55:26

Title: What has caused this stripey pattern on of the wall of this building?
Post by: shoshone on 28/11/2015 09:55:26

Hi there, I'm starting with a brief introduction.
Geology is not my area of expertise, and to be honest I'm not even sure this is related to the board, but I'm taking a shot anyway. Apologize if this is out of topic.

Field is architectural, for a university course of building restoration and consolidation: part of the course is about Lithology and Geology.
I'm supposed to make a survey of the facades of my building, and map all the damages due to weathering, etc.

I've encountered something peculiar on one of the facades, and I haven't seen anything similar on books and manuals. Can anyone help me identify this kind of damage?
It's the 'tiger stripes' on the plaster between the two columns on the left. Just under it there is an irrigation ditch.

The building is a mill built in masonry (brick units) and plaster. Location is the Po Valley in the north of Italy.

Thanks!

Title: Re: Building wall damages: what is this?
Post by: RD on 28/11/2015 11:58:24

Ventifacts on stone can have a sand-dune-like parallel ridges ...

(https://upload.wikimedia.org/wikipedia/commons/thumb/0/09/Ventifact_at_Ventifact_Ridge_in_Death_Valley_NP%283%29.JPG/311px-Ventifact_at_Ventifact_Ridge_in_Death_Valley_NP%283%29.JPG)
https://commons.wikimedia.org/wiki/File:Ventifact_at_Ventifact_Ridge_in_Death_Valley_NP%283%29.JPG

Title: Re: Building wall damages: what is this?
Post by: shoshone on 28/11/2015 15:58:05

Thanks! I will inquiry on that! ;)

Title: Re: Building wall damages: what is this?
Post by: Bass on 28/11/2015 17:42:52

Are the stripes raised? or just discolored?

Title: Re: Building wall damages: what is this?
Post by: shoshone on 29/11/2015 10:55:47

They are just colored!

Title: Re: What has caused this stripey pattern on of the wall of this building?
Post by: chintan on 29/11/2015 12:54:58

Some kinda fungus or algae from plants and the atmosphere also looks humid to so have a piece of it and take it to chemist or biologist

Title: Re: What has caused this stripey pattern on of the wall of this building?
Post by: RD on 01/12/2015 13:46:27

Quote from: chintan on 29/11/2015 12:54:58

... Some kinda fungus or algae...

We've had stripey-fungus on this forum previously , see ...
http://www.thenakedscientists.com/forum/index.php?topic=49171.0;nowap

Title: Re: What has caused this stripey pattern on of the wall of this building?
Post by: puppypower on 02/12/2015 12:33:01

Quote from: chintan on 29/11/2015 12:54:58

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. 

Title: Re: What has caused this stripey pattern on of the wall of this building?
Post by: shoshone on 08/12/2015 15:12:37

Thanks everyone for your inputs.
Will check with teacher at the end of the week and let you know what she thinks!