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SALT EFFLORESCENCE
SALT EFFLORESCENCE

Sample

Adjacent wall to the staircase entrance to the Castle of Castellet i la Gornal. Alt Penedès. Barcelona

Pathology Causes

Repeated cycles of salts crystallization.

 

The rounded shape of chlorides and the amoeboid appearance of the redissolution indicate repeated cycles of wet conditions, in this case due to the proximity of a cavity, an internal leaking and the southerly orientation of the wall. The habits and crystalline forms of salt efflorescences indicate a process of rapid crystallization  in a substrate highly saturated with water (very wet conditions). These results are consistent  with the model of a wall that suffers internal leaks.


Visual Image

Author: CETEC-patrimoni

Description: Salt efflorescences inside the alveole of the ashlar.


Image detail / macro

SALT EFFLORESCENCE
Author: CETEC-patrimoni
Magnification: X20

Description: The salts present microcrystalline aggregates of different types and sizes (mainly sand size) by stereoscopic microscope. The colours of the crystals are varied, ranging from transparent (chlorides), white, amber, through to yellow (other types of chlorides and sulphates).


Microscope Image

SALT EFFLORESCENCE
SALT EFFLORESCENCE
Author: CETEC-patrimoni
Magnification: Figure 1: x1300. SEM-EDS. Backscattered electron image. Figure 2: x800. SEM-EDS. Backscattered elect

Description: Figure 1. Crystalline aggregates of lenticular gypsum -CaSO4.2H2O-.

Figure 2. Aggregates of crystalline chloride (halite -NaCl-) pseudo-cubic shapes, rectangular, amoeboid or rounded sides.


Associated Pathologies

Alveolization.

Differential erosion.

Flaking.

Sanding.


Other Tests

XRD indicates a complex salts composition (chlorides, phosphates and sulfates).

Observations

These salts are a result of products of the reaction  between the mixture of  bird waste  with sulphates or carbonates from the hydraulic mortars, specifically the two amorphous and colloidal phosphate minerals, similar to apatite -Ca5Cl(PO)3-.

Bibliography

ARNOLD, A. & KUENG, A. (1985). Cristallization and Habits of Salt Efflorescences on Walls. Part I, Methods of Investigation and Habits. Vth hitemational Congress on Deterioration and Conservation of Stone. Lausanne. pp. 255-268.

 

ARNOLD, A. &  ZEHNDER, K., (1985), Cristallization and Habits of Salt Efflorescences on Walls. Part.II, Conditions of Cristallization. Vth International Congress on Deterioration and Conservation of Stone, Lausanne. pp. 269-277.
 
CHAROLA, A. E. (2000). Salts in deterioration of porous material: an overwiew. JAIC, 39. pp. 327-343.
 

ICOMOS-ICS (2008). Illustrated glossary on stone deterioration pattern.

http://international.icomos.org/publications/monuments_and_sites/15/pdf/Monuments_and_Sites_15_ISCS_Glossary_Stone.pdf 


Author

Núria Guasch Ferré. nuriaguaschferre@gmail.com

Llicenciada en Ciències Geològiques. Màster Oficial en Conservació i Restauració de Béns Culturals, especialització en Conservació i Restauració d’Escultura i de Materials Arqueològics


Institution or Company

Cetec-patrimoni


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