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Custos aeris dew point monitor for cultural assets like glass paintings

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As early as 1990-1996, extensive studies on the structure and effect of protective glazing were carried out in a Franco-German research project on the conservation of natural stones and glass paintings.The aim was to develop basic rules for the protection efficiency of ventilated exterior protective glazing.
In 2016, as part of a DBU project on climate stabilisation for protective glazing in St. Sebald, it was explicitly pointed out that only a limited number of generally applicable basic rules for the construction of exterior protective glazing can be derived, but that in any case climate control must take place in the air gap.

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Custos aeris dew point monitor for cultural assets like glass paintings

  1. 1. Custos Aeris dew point monitor for the protection of historical glass paintings By Dr. Hans-Jürgen Daams (Hajuveda Heritage) and Michael Robrecht (iXtronics) © Hajuveda Heritage and iXtronics GmbH 2019
  2. 2. 2 31outlook7 26Interpretation of measurement results 6 22Assembly of Custos Aeris 5 19Structure of Custos Aeris 4 13some physical aspects of the dew point 3 6Examples of damage to church windows 2 3Aim of the project 1 Custos Aeris dew point monitor for the protection of historical glass paintings
  3. 3. 3 31outlook7 26Interpretation of measurement results 6 22Assembly of Custos Aeris 5 19Structure of Custos Aeris 4 13some physical aspects of the dew point 3 6Examples of damage to church windows 2 3Aim of the project 1 Custos Aeris dew point monitor for the protection of historical glass paintings
  4. 4. 4 Motivation for the project ▪ As early as 1990-1996, extensive studies on the structure and effect of protective glazing were carried out in a Franco- German research project on the conservation of natural stones and glass paintings. (/ros12/). The aim was to develop basic rules for the protection efficiency of ventilated exterior protective glazing. ▪ In 2016, as part of a DBU project on climate stabilisation for protective glazing in St. Sebald, it was explicitly pointed out that only a limited number of generally applicable basic rules for the construction of exterior protective glazing can be derived, but that in any case climate control must take place in the air gap. Preparatory work for the project Picture sources: https://www.sebalduskirche.de/baugeschichte/
  5. 5. 5 Goal of the project: Development of a non-contact dew point measuring device ▪ The necessity of permanent monitoring of the glass surfaces in the air gap led to a new project (/San17/). ▪ The aim of the project was to develop a permanently monitoring sensor with the following individual objectives: ▪ Non-contact measurement technology ▪ Easy to assemble ▪ No cables and installation effort ▪ no special knowledge ▪ Online monitoring of measurement results Dew points on historicel window inside, historical window and protective glazing in the airgap
  6. 6. 6 31References, contacts, bibliography7 26Interpretation of measurement results 6 22Assembly of Custos Aeris 5 19Structure of Custos Aeris 4 13some physical aspects of the dew point 3 6Examples of damage to church windows 2 3Aim of the project 1 Custos Aeris dew point monitor for the protection of historical glass paintings
  7. 7. 7 Damage mechanisms in historical glass paintings ▪ Historical glass paintings are exposed to various damage mechanisms. Examples of this are (/ros12/): • Leaching phenomena of potassium- containing glasses under the influence of water • air contaminants • Black crusts on the outside of the glass containing fly ash • microorganisms • Browning of glass by manganese oxidation
  8. 8. 8 Damage to historical glass paintings caused by condensate ▪ In the dusting of the windows, the traces of the water course can be clearly seen on the inside of the glass painting. ▪ Paintings are so directly attacked. ▪ Image and text from (/gla10/) Water run marks on the inside
  9. 9. 9 Damage to historical glass paintings caused by condensate ▪ Increased water ingress leads to increased salt washout on the inside of the glass. ▪ The salts can in turn combine with water to form unfavourably acidic solutions. ▪ Image and text from (/gla10/) Salt washout on the inside of the glass
  10. 10. 10 Damage to historical glass paintings caused by condensate ▪ The water increases the risk of painting losses. ▪ The white edges on the contours speak for a new corrosion process and thus for partial breaking out of individual slabs. ▪ Image and text from (/gla10/) Water causes painting losses
  11. 11. 11 Damage to historical glass paintings caused by condensate ▪ Loss of painting due to condensation of water in the form of plaice ▪ Image and text from (/gla10/) The plaicelike detachment of painting
  12. 12. 12 Problems due to faulty protective glazing ▪ The lateral mortar seal has come loose and there is no seal left. ▪ The glass is damaged by external influences and shows cracks in places. The poetry is partially lost. ▪ The ventilation slots are out of order in many places. They are either clogged or have been directly sealed. ▪ An oily mass runs out between the floor iron and the cover rail, this can be linseed oil putty or a corresponding substitute. ▪ Due to the missing lead sheath, oil penetrates into the gap of the SVG. The lamination is loosened. The protective function is lost as a result of the separation, and microorganisms can also accumulate in the cavities. ▪ Source: (/gla10/) Continuous monitoring of climate and dew points in the air gap is essential:
  13. 13. 13 31outlook7 26Interpretation of measurement results 6 22Assembly of Custos Aeris 5 19Structure of Custos Aeris 4 13some physical aspects of the dew point 3 6Examples of damage to church windows 2 3Aim of the project 1 Custos Aeris dew point monitor for the protection of historical glass paintings
  14. 14. 14 Mollier h-x diagram for condition determination • The horizontal lines indicate the temperature in degrees Celsius. • The vertical lines indicate the absolute water content in g water per kg air. • We don't need the green and red lines right now. • The curved lines are the relative humidities. • The 100% line for the relative humidity separates the areas of water dissolved in air from the fog areas. • Below is fog or condensate • Above there is water dissolved in air Determination of water and water vapour dissolved in air (condensate)
  15. 15. 15 Mollier h-x diagram for determining the condition of the air • Question: At what temperature will fog or condensate form? • Example: Our air at 20 degrees Celsius may have a relative humidity of 50 %. (see red circles) • The red dot in the diagram shows this state point. • The water content of the air is about 7 grams of water in 1 kg of air. • At the same water content we cool the air until it is on the border to the fog/condensate (red arrow downwards). • The temperature when condensate or mist occurs is then obtained by looking at the horizontal line. It's about 9 degrees. This is then the dew point temperature. Determination of the dew point temperature
  16. 16. 16 Mollier h-x diagram for determining the condition of the air ▪ The dew point temperature can of course also be calculated: ▪ Go on for this: ▪ <font color="#ffff00">- =https://rechneronline.de/barometer/taupun kt.php=- proudly presents Calculation of dew point temperature
  17. 17. 17 Application to a window pane • The glass window (or alternatively a wall) is represented by the vertical bar in light blue. • To the left of it is the indoor air in the building, here with 20 degrees Celsius and 50% relative humidity. • To the right of it is the cold outside air. • Since the insulation properties of the window are unknown, the external conditions are not relevant. • The glass temperature towards the interior is relevant. • The dew point was calculated at 9.26 degrees C. • If the glass temperature falls below this value, condensate escapes. Formation of condensation water on a glasswindow
  18. 18. 18 Basic requirement for a measuring system ▪ The measuring system must measure the air temperature and the relative humidity of the air in the area close to the window. ▪ The measuring system must be able to measure the glass temperature without contact (to avoid damage to the historical glass painting). ▪ Church windows are mounted at great heights (scaffolds), so the installation of the device must be simple. ▪ The sensors must be integrated. Ex-ternal sensors increase the assembly effort. ▪ Cables are undesirable. ▪ Eventually the scaffolding will be dismantled. The measuring instrument must nevertheless continue to supply data and have an autonomous power supply. measured quantities
  19. 19. 19 31outlook7 26Interpretation of measurement results 6 22Assembly of Custos Aeris 5 19Structure of Custos Aeris 4 13some physical aspects of the dew point 3 6Examples of damage to church windows 2 3Aim of the project 1 Custos Aeris dew point monitor for the protection of historical glass paintings
  20. 20. 20 Monitoring of condensate formation in the gap between historically valuable lead glazing and protective glazing ▪ On the right in the picture you can see the historically valuable lead glazing. To the right of it is e.g. the interior of the church. ▪ The protective glazing can be seen on the left. It is usually mounted from the outside at the former location of the lead glazing. ▪ The iron is inserted into the wall. The cover rails serve to guide and stabilise the glazing. ▪ The gap distance can be adjusted via the middle threaded rod. ▪ The air gap module of the measuring device must now be so small that it still fits into the gap. The main module must be installed in the area near the window in the interior of the church in the immediate vicinity of the air gap module. Cross section of the structure for protective glazing
  21. 21. 21 Monitoring of condensate formation in the gap between historically valuable lead glazing and protective glazing Sketch of the desired structure
  22. 22. 22 31outlook7 26Interpretation of measurement results 6 22Assembly of Custos Aeris 5 19Structure of Custos Aeris 4 13some physical aspects of the dew point 3 6Examples of damage to church windows 2 3Aim of the project 1 Custos Aeris dew point monitor for the protection of historical glass paintings
  23. 23. 23 Monitoring of condensate formation in the gap between historically valuable lead glazing and protective glazing ▪ The air gap module is pushed via clamps onto the cover rail inside the lead glazing. ▪ The cable entry to the main module is made past the inner and outer cover rail (not shown). ▪ The main module is also clamped. ▪ After switching on the main module, the data collection is carried out every 15 minutes. ▪ Air temperature and humidity are measured in the air gap and in the area of the lead glazing close to the glass (see slots in the modules). ▪ The glass temperatures of protective glazing, lead glazing on the air-gap side and lead glazing on the church side are measured. Structure of the measurement technology in cross-section
  24. 24. 24 Monitoring of condensate formation in the gap between historically valuable lead glazing and protective glazing Representation of the structure on the model. The total assembly takes no more than 3 minutes. mobile phone antenna
  25. 25. 25 Monitoring of condensate formation in the gap between historically valuable lead glazing and protective glazing ▪ When the device is switched on, it searches for the best connection to a mobile network. ▪ If this is found, the device automatically logs into the cloud. ▪ Every morning at 08:00 all data of the last day will be radioed into the cloud. ▪ With a user name and password, the user can dial into the cloud via an Internet browser and view all the data collected so far. ▪ The battery life is at least one year and experience has shown it to be 3 years, depending on the solar radiation on the solar module. Data transfer to the cloud and battery life
  26. 26. 26 31outlook7 26Interpretation of measurement results 6 22Assembly of Custos Aeris 5 19Structure of Custos Aeris 4 13some physical aspects of the dew point 3 6Examples of damage to church windows 2 3Aim of the project 1 Custos Aeris dew point monitor for the protection of historical glass paintings
  27. 27. 27 Available Graphics in the Cloud Air temperature and humidity
  28. 28. 28 Available Graphics in the Cloud Temperatures of glass surfaces and dew point temperatures
  29. 29. 29 Available Graphics in the Cloud Dew point undershoots and monthly statistics of dew point undershoots in %.
  30. 30. 30 Available exports of data • Data tables in . csv format. This allows a conversion to Excel. • Graphics in . jpeg or . pdf format monthly and for the entire term Graphics and data can be exported
  31. 31. 31 31outlook7 26Interpretation of measurement results 6 22Assembly of Custos Aeris 5 19Structure of Custos Aeris 4 13some physical aspects of the dew point 3 6Examples of damage to church windows 2 3Aim of the project 1 Custos Aeris dew point monitor for the protection of historical glass paintings
  32. 32. 32 References, contacts, bibliography references ▪ Cologne Cathedral ▪ Wiesenkirche in Soest ▪ Naumburg Cathedral ▪ Minster in York ▪ 2 Churches in Poland ▪ Stained glass painter company Peters in Paderborn ▪ contacts ▪ Hans.daams@hajuveda.solutions ▪ Michael.robrecht@ixtronics.com ▪ web appearances ▪ https://www.hajuveda.solutions ▪ https://ix.ixtronics.com/de/ ▪ https://custosaeris-d.blogspot.com/
  33. 33. 33 References, contacts, bibliography Bibliography: ▪ /Fri16/ Fritsch, A. (2016). Possibilities of a climate stabilization for glass painting stocks damaged by anthropogenic environmental influences using the example of St. Sebald in Nuremberg. Parish office Nuremberg inner city communities St. Sebald. Nuremberg: DBU 31770/01. ▪ /Gla10/ Peters Glass Painting, Restoration Department. (2010). Classification of the condition of glass paintings in churches. Restoration Department. Paderborn: glass painting Peters, restoration department. ▪ /ros12/ Rosant, P. M.-M. (1997). Measurements, calculations and experiments on exterior protective glazing in historical glass painting. Summary report of the working groups Oidtmann, FI for silicate research, Laboratoire de thermique, Laboratoire de Mecanique des fluides, Universite de Marne-la-vallee. Paris: exe Production. ▪ /San17/ Sander, C. (2017). Development and model application of a new sensor system for monitoring the sustainable effectiveness of protective glazing for glass paintings endangered by anthropogenic environmental influences using the example of the Wiesenkirche in Soest. Glasmalerei Peters GmbH. Paderborn: DBU 30751 / 45.

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