Custos Aeris: New evaluations for the preventive protection of historical lead glazing (Part 4)
Risk of temperature and humidity gradients
Particularly with solar radiation very high gradients in glass temperature, air temperature and relative humidity can occur. They can lead to damage of the historical glass painting. Even though there are no limit values for these gradients so far, they are now evaluated and displayed to give a feeling for the values.
Risk Temperature gradient
The following picture shows the gradients of the glass temperature of the historic glass on the church interior side and on the air gap side as well as the gradients of the protective glazing.
|Gradient of glas temperature at historical lead glazing in K/15min|
An increase in the gradients is clearly visible for the summer months. However, since the window is on the north side, no extreme gradients are visible.
The next picture shows the gradients of air temperatures:
|Gradien of air temperature around historical glazing with protective glazing in K/15min|
Here the summer-winter effect is also visible and the gradients are lower for the air temperatures on the inside of the church (blue) due to damping effects.
Risk Humidity gradient
As expected, the summer-winter effect is also visible here and the gradients of humidity inside the church are lower than those in the air gap. Maximum values of the change are about 7.5% relative humidity in 15 minutes.
|Gradient of relative humidity for historical lead glazing in %/15min|
This work is a separate continuation of the DBU project DBU Aktenzeichen 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 supported and completed by the DBU. We would like to take this opportunity to thank you once again for supporting the project.
Michael Robrecht and Markus Böger, iXtronics GmbH, Paderborn
Hans Daams, Hajuveda Heritage, Monschau