Academic thesis

Antonia Magdon: Einfluss früherer Hydrophobierungsmaßnahmen auf die nachträgliche Entsalzung von Sandsteinen Back
Language: Original   -   Translation
Abstract: It was and to some extend is common to apply hydrophobic agents to stone objects during restoration measures. This leads to difficulties when other water based applications like de-salination compresses, should be conducted. Therefore methods to handle with water repel-lent surfaces during restoration are needed.

The primary object of this thesis is the bridging of hydrophobic sandstone surfaces by means of tensides. It was examined if the reduction of the surface tension of water causes a better wettability of salt loaded objects with hydrophobic properties. An improved wettability is the basis for the desalination utilizing compresses.

After preliminary tests in terms of dilution series, wettability from water repellent surfaces and solubility of sodium chloride in tenside solution, five of ten non-ionic tensides [Marli-pal 1618/25 (Kremer-Pigmente), Lutensol ON50, ON60, ON70, TO7 (BASF)] were selected for further analysis.

Three approaches to measure the success of desalination under the influence of the ten-sides were followed:
1) gravimetric comparison of samples before and after treatment
2) chloride detection utilizing silver nitrate and nitric acid
3) measurement of electric conductivity
The tests were carried out on similar sandstone tiles. For desalination the tensides in differ-ent dilutions, were mixed with cellulose fibres (Arbocel) to compresses. Desalination pro-ceeded in two different ways. On the one hand the compresses were applied on the sample under normal moist condition and left on the sample until they were nearly dry. On the other hand enforced desalination was used. Parallel samples without tenside add- ons were tested as reference.

The results of these analyses are positive and meet one’s expectations in large parts. The wettability of water repellent surfaces is ensured by the use of tensides. For all tensides en-forced treatment resulted in a higher desalination rate with Lutensol ON70 achieving the best results. This fits to the findings of the electric conductivity test. On the other side Lutensol TO7 showed similar or even worse results as the reference measurements.

The reduction of salt by the normal method was always worse then with the enforced method with Lutensol ON70 also showing the best results. Performance of Marlipal was below the reference values whereas the others tensides were not showing strong differences to the reference.

Desalination was measured as the difference of weights before and after treatment with ten-sides. As the material suffered during the treatment, for example damages of rough edges, the results are biased to some extent. Foam formations can be observed if the samples are brushed with water.

The results are promising. It could be shown that with the use of tenside the performance of desalination was increased. This also can be an indication for the use of tensides, increasing the wettability of hydrophobic surfaces, among other restoration techniques like replenish-ments with mortars.

As the time of this thesis was limited the enforced test series were run with just one sample per tenside and concentration. Before a practical application can be recommended further analysis with more iterations, samples and tensides has to be carried out.


Keywords: Tenside, Entsalzung, Salzverminderung, Kompressen, hydrophob, Hydrophobierung, Hubertuskapelle Sehlde
Table of contents: Danksagung 4
1 Abstract 5
2 Einleitung 6
2.1 Zielsetzung und Erwartungen 7
3 Tenside 8
3.1 Wirkung und Eigenschaften 8
3.2 Benetzung und Spreitung 10
3.3 Tensidgruppen 12
3.4 Tenside in der Restaurierung 13
4 Salzverminderung 17
4.1 Begriffserklärung 17
4.2 Methoden zur Salzbehandlung 17
5 Ausgangssituation 20
5.1 Schadensbilder 20
5.2 Wasseraufnahme mittels Mirowski- Prüfröhrchen 21
5.3 Allgemeines zur Wasseraufnahme 22
5.4 Analysierte Salze 25
6 Ausgewählte Tenside 26
6.1 Warum nichtionische Tenside? 26
6.2 Restauratorenbedarf 26
6.3 BASF- Lutensole 27
7 Vorgehensweise in der Werkstatt 30
7.1 Probenmaterial 30
8 Vorversuche zu Tensiden 34
8.1 Verdünnungsreihen 34
8.2 Tröpfchentests zur Benetzbarkeit 36
8.3 Leitfähigkeitsmessungen 39
8.4 Ermitteln des pH- Wertes 42
8.5 Lösungsversuche- NaCl in Tensid 42
8.6 Auswertung der Vorversuche 43
9 Hauptversuche 47
9.1 Vorarbeit 47
10 Untersuchungen 51
10.1 Versuchsaufbau- einfache Kompressenbehandlung 51
10.2 Versuchsaufbau- erzwungene Entsalzung 53
10.3 Versuchsaufbau- Chloridnachweis und Leitfähigkeitsmessungen 54
11 Ergebnisse 55
11.1 Gewichtsnachweis 55
11.2 Chloridnachweis 60
11.3 Leitfähigkeiten 61
11.4 Versuch zum Erkennen von Rückständen 63
11.5 Beobachtungen zur Wirkung auf den Sandstein 64
11.6 Zusammenfassende Auswertung 65
12 Objektbezug 67
12.1 Objektbeschreibung und Geschichte 67
12.2 Notwendigkeit von Maßnahmen 69
12.3 Anlegen einer Musterachse 69
12.4 Auswertung 70
13 Diskussion 71
14 Ausblicke 73
15 Anhang 74
15.1 Datenblätter 74
15.2 Tensidkatalog- verwendeter Tenside mit Datenblättern 79
16 Verzeichnisse 91
16.1 Literatur 91
16.2 Quellen aus dem www 91
16.3 Sonstige Quellen 92
16.4 Abbildungen 92
16.5 Tabellen 94


  • academic institution: HAWK Hochschule für angewandte Wissenschaft und Kunst Hildesheim/ Holzminden/Göttingen
  • kind of theses:  Diplomarbeit
  • main Tutor:  Prof. Jan Schubert
  • assistant Tutor:  Prof. Dr. Thomas Thielmann
  • date:  2008
  • Language:  Deutsch
  • pages:  95
  • pictures:  70
Antonia Magdon
antonia.friedrich@[Diesen Teil loeschen]


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