Documentation-Sampling

Author: Hans-Jürgen Schwarz
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Abstract

Each analysis should begin with sampling and its documentation. The quality of the sampling is paramount in determining whether the investigation will provide the required information to develop appropriate conservation measures. The documentation captures the metadata of the samples and assigns each sample a unique collection site.

Introduction: Sampling

Each sampling represents an interference on the object. In general, sensitive objects such as wall paintings sampling should be carried out by conservators or at least jointly with a conservator. The presence of the analyst at the sampling is essential for obtaining the required information from the analysis and investigation. The accuracy of an analysis depends directly on whether the sample is representative of the object. The samples are taken to allow answering a specific question, not to carry out an analysis. Therefore, the sample type, size and location must be chosen so as to provide the required answer.

The number of samples depends on the question. Since chemically different salts may occur in the same shape and the same salt efflorescence in different forms, it is advisable to sample each crust or efflorescence. When salt-induced damage is suspected, it is often advisable to take samples along horizontal, vertical or depth profiles to capture the distribution of the damaging salts so as to be able to plan appropriate conservation measures.

Pure salt samples are easier to analyze than salt mixtures or contaminated samples. For analysis, the pure salts are removed without their substrate. Only a very small amount of salt is needed for their analysis.

In addition to surface samples, drilling dust [Steiger.etal:1998]Title: Salze in Natursteinmauerwerk - Probennahme, Messung und Interpretation
Author: Steiger, Michael; Neumann, Hans-Herrmann; Grodten, Torsten; Wittenburg, Christian; Dannecker, Walter
or core samples may be required to provide the required answers.

If moisture droplets are found on the surfaces, these should also be examined to see whether their presence is due to water vapor condensation or salt hygroscopicity.

The time at which the sampling is carried out plays a role, as there is a correlation between the type of salt crystallizing and climate conditions. Therefore, climate conditions should be documented at the time the mapping and sampling is done. Ideally. Sampling time and place should be chosen as a function of climate conditions. The samples should be analyzed immediately after collection to avoid changes, such as their hydration or dehydration.

Sample containers that are suitable for small samples are water vapor-tight, sealable plastic bags, tubes or little boxes. Gelatin capsules are not suitable for storage of salt-containing samples, since moisture can escape or penetrate.

Introduction: Documentation

Sampling should always be documented. The documentation should include:

• Name of sampler (for inquiries).
• Sampling time (date, time).
• Climatic conditions (e.g., T, RH, sun, shade, etc.).
• Exact sampling point (entry on building map or sketch, and photography, general and in detail).
• Description of the sample and the substrate.
• Information required from the analysis, i.e., what is the question?
• Details important for further investigations and interpretation.

Literature

[Steiger.etal:1998]

Steiger, Michael; Neumann, Hans-Herrmann; Grodten, Torsten; Wittenburg, Christian; Dannecker, Walter (1998): Salze in Natursteinmauerwerk - Probennahme, Messung und Interpretation. In: Snethlage, Rolf (eds.): Jahresberichte Steinzerfall - Steinkonservierung 1994-1996, IRB-Verlag, 61-91.

crystallization of a dissolved salt

relative humidity