Custos Aeris: New evaluations for the preventive protection of historical lead glazing (Part 3)

Risk Temperature and humidity alternating stress


Risk of thermal cycling

Thermal cycling around 0 degrees Celsius leads to the formation of ice and condensation. Solid and liquid phases change constantly. This leads to mechanical damage to the gel layer and cracks, crusts, cracking and detachment /Hör 06/. There are still no limits as to how often this may happen per defined time unit except "as little as possible". The following diagram shows the number of changes per time unit for protective glazing in a cathedral:

Number of Thermal Cycles around 0 degrees C


Risk of moisture cycling

Moisture cycling around 80% leads to salt crystallization, cracking of the gel layer and intensification of corrosion /Hör 06/. Here too, there are no limit values, so that again the number of changes per unit of time is shown:

Number of moisture Cycles around 80% relative humidity


References:

Garrecht, H., Hahn, O. & Kappes, K. e., 2010. model test for gap temperature control at the Divi Blasii church in Mühlhausen, Germany, s.l.: s.n.
Hör, M. u. F. A. e., 2016: Possibilities of climate stabilization for stained glass collections damaged by anthropogenic environmental influences using the example of St. Sebald in Nuremberg, Nuremberg: St. Sebald, Nuremberg.
Hör, M. u. S. J., 2006. building physics investigations on the endangerment of the stained glass inventory in Nuremberg's Sebalduskirche, possibilities and limits of the effectiveness of exterior protective glazing, Nuremberg: s.n.
Schumacher, C. M., 2010. The glazing of the Protestant St. George Chapel in Fuhlenhagen, Koblenz: Büro Dr. Rauch.
Torge, M., 2011: "Exemplary evaluation of restoration and conservation measures for historical glass paintings with severe damage caused by anthropogenic influences", Berlin: Final report DBU Az 27312-45.


Acknowledgement:

This work is a separate continuation of the DBU project DBU file number 30751 "Development and exemplary application of a new sensor system for monitoring the sustainable effectiveness of protective glazing for stained glass endangered by anthropogenic environmental influences using the example of the Wiesenkirche in Soest", which was funded and completed by the DBU. We would like to take this opportunity to thank you once again for supporting the project.

Contact person: 

Michael Robrecht, iXtronics GmbH, Paderborn
Hans Daams, Hajuveda Heritage, Monschau

Direct contact: 

hans.daams@hajuvda.solutions
michael.robrecht@ixtronics.com

Web addresses: 

https://www.hajuveda.solutions
https://ix.ixtronics.com/de/

Blog: 

https://custosaeris-d.blogspot.com

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