## 2 Materials and Methods
### Experiments  
Taking into account the sensitivity of deformation and the pressure difference in the gap to the linear dimensions of IGUs described in [8; 9], it was found that the use of too large a sample was not justified. This was because as the linear dimensions increase there is a significant gas interaction, which requires a large amount of injected gas to cause a significant deflection of the panes and induce stress in the glass. Preliminary analyses have shown that using models with widths of \(400\div 600\) mm is advisable in this context [8; 9]. The calculations by [PERSON] [3] showed that the critical length for a square IGU 6-16-6 is 500 mm.  
Considering the above findings, a double-glazed IGU with a size of 500 mm \(\times\) 500 mm was used. It was composed of two toughened glass panes with a nominal thickness of 6 mm and a 16 mm wide gap. A standard aluminum spacer and a structural silicone outer seal were used. The panes were made of regular soda-line silica glass.  
Before conducting experiments, the model was prepared by drilling two holes in the spacer, inserting short copper pipes into the holes, and sealing the connections (Figure 1a). In this way, an unsealed IGU filled with air was obtained. Flexible (silicone) conduits with an internal diameter of 4 mm were mounted on the ends of the pipes, to which the following devices were attached: a precise syringe (with a specific volume) and a pressure sensor. To measure the pressure difference, the TESTO 400 device [36] with the ability to record in time the absolute pressure in the gap and the pressure difference between the gap and the surroundings with a frequency of 1 Hz was used.  
On the perimeter of the glass panes, solid rods with a diameter of 10 mm were glued on both sides of the IGU. Near the center of the model, strain gauges with a base of 10 mm were attached to both component glass panes and wires were guided through holes made in the boards (Figure 1b).  
The scheme of the test stand is shown in Figure 2. The IGU model was placed between two 22 mm OSB boards and stabilized by screwing them with four bolts outside the sample outline. The deflection was measured on both sides of the IGU in the middle of the model through holes in the boards. Linear Variable Differential Transformer (LVDT) sensors were placed on magnetic bases attached to boards with metal connectors, preventing the uncontrolled displacement of the IGU model in relation to the measurement system. During the test, the deflection and stress in the center of the component panes were measured using the TMX-0208 SE device with a measurement frequency of 10 Hz [37]. The IGU model was placed in a vertical position to avoid pane deflection due to its self-weight.  
Figure 1: Details of the test stand: (**a**) mechanical supports and silicone conduits for gas exchange in the gap; (**b**) strain gauges mounted to the panes.  
A single test series consisted of injecting or withdrawing a defined air volume into/from the IGU gap. During the test, the following quantities were measured: over- or under-pressure in the gap, out-of-plane deflection of the panes, and stress in the glass in the center of the model. After the gas was injected/withdrawn into/from the gap, the measurements were carried out for 5 min. The test campaign consisted of eight test series, including injecting and withdrawing the air from the gap ranging from 50 mL to 200 mL with a 50 mL interval. Five repetitions were performed for each test series.