The IGR Institut für Glas- und Rohstofftechnologie (Institute for Glass and Raw Materials Technology) is a globally recognised, DIN EN ISO/IEC 17025:2018 accredited, service provider for the glass industry, raw material producers and food technology. As a reliable testing laboratory, IGR also routinely offer its customers seed and blister content analyses.
The typical blister content analysis is performed using gas chromatography, mass spectroscopy and/or Raman spectroscopy and covers the gases H2, Ar, O2, N2, CO2, SO2, CO, COS, H2S, CH4 as well as H2O.
In this context, it is particularly important that all gases, explicitly including all of the above-mentioned sulphur modifications, as well as the pressure, are analysed during the blister content analysis, as this is the only way to obtain a meaningful interpretation of the origin.
In addition to gas content analysis, IGR also use microscopy to examine the inner surface (e.g. crystals or droplets) as well as the shape, size and location of the seeds or blisters, enabling us to provide tips on how to avoid these gas inclusions in the future.
If other abnormalities such as streaks or particles are found in the surrounding area of the blisters and seeds, a SEM-EDX examination is carried out in order to obtain additional information about the cause of the blister formation.
IGR interprets the results based on the macroscopic and microscopic examinations carried out, the results of the blister content determination and the information received from the client, such as melting tank and raw material parameters and cullet qualities. This enables IGR to interpret the origin of the blisters formation so that suggestions on how to modify the melt to prevent blister formation in the future can be developed and communicated.
From time to time, IGR analyses very special blisters, known as vacuum blisters (also called vacuoles), which are blisters without crystalline or gaseous content. They occur when the glass cools too quickly during production. These special blisters are not present during the forming process, but only develop afterwards. Physically and chemically dissolved gases in the glass have no way (high viscosity, low temperature, no time) to diffuse into this cavity. These blisters can also no longer float up (viscosity > log 10^7.6). The analyses revealed no crystals and no gas content, so they are empty.
Another special feature of the vacuoles is that they disappear immediately when the glass is reheated to a temperature of approx. 650 to 680 degrees Celsius. One of the IGR customers has provided a video in which this process can be observed in detail.
How? When watching the video, pay attention to the two bright spots on the left and right. The first blister (left) disappears at second 16, while the second (right) is no longer visible at second 28.
The IGR team looks forward to working with you and your company in the future.