Author: Steffen Laue
English version by Christa Gerdwilker
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The aim of preliminary investigations on an object is to gain an understanding of the building's deterioration issues prior to commissioning extensive salt and moisture analysis.
Case specific project planning is essential before commissioning any actual analysis. An appropriate project management structure should be developed to guide and oversee the running of the planned intervention. The type and extent of building investigations always depend on the specific aim of the restoration or renovation measures. The project objectives define the fundamental planning aspects of the individual project phases as well as the time, cost and financial budgeting. Prior to executing expensive examinations, initial preliminary investigations can save time and money. Preliminary investigations can be:
It is fundamental that any investigation should start with documentary research into the history of the building; this includes the construction as well as its use over time, recorded problems, and any restoration and renovation interventions it underwent, referred to as anamnesis. Potential sources of documentary evidence are: owners (over the years), archives (city, council, county, state, church), heritage organizations and possibly other public or private institutions.
Close examination of the object
Close examination and the recognition of deterioration patterns can provide the first clues of the amount of damage and its extent within a building. A trained practitioner, who has gained much experience from different objects, knows which parts of a building to investigate and may be able to formulate preliminary theories regarding the cause(s) of decay which can then be confirmed through analysis. The preparation of sketches and drawings of the building and its deterioration patterns, i.e., condition survey of the building, requires close examination that serves to link the damage to potential deterioration problems.
Interviews with object stakeholders, such as owners, users and heritage organizations, and consultation with them may provide further useful indications as to the construction, use and restoration history of the object and/or the materials used. It is quite possible that object samples have been taken in the past and that analysis had been carried out at the time.
The following explorative investigations can provide a better evaluation of the problem:
- Examination of efflorescence (crystallized salts) with a magnifying lens.
- Crushing of salts between fingers in a small transparent sample bag: if water drops separate out, the salt is hydrated (e.g., mirabilite).
- Placing suspected salts onto a knife tip and heating this from below will differentiate salts and biogenic materials, since the later would burn or carbonize, not so the salts.
- Placing a pH paper strip in contact with liquid drops on a building surface allows to identify alkaline reacting substances.
- Sampling liquid drops on a building surface with blotting paper and analyzing them in laboratory for various ions.
- Instruments like a “Protimeter” or “Hydromette” are not suitable for the analysis of salts but may be used for comparative evaluation of different dampness levels within a building. These instruments are not able to provide quantitative moisture content data.
- Evaluation of salt content by conductivity measurements.
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