The second solution named “mix 2” refers to Rotundine solution based on water, condensed tannins, and others additives. This solution was also whipped up mechanically.
“Mix 2” was then progressively added to “mix 1” and continuously stirred until a homogeneous emulsion was obtained. The plastic beaker containing the emulsion was covered with aluminum foil and put into an oven at 75 °C for 2 h. Two samples were instead cured 2 min in a microwave oven of 700 W power (Bluesky BMO17Z-13, France).
Foams have been prepared with different quantity of water to adjust the viscosity. Two control foams with albumin alone were prepared without tannin and two different quantities of hardener as a comparative reference.
2.3. Foams characterization
2.3.1. Climate chamber
After cutting, the samples were placed in a climate chamber at 20 °C and at a relative humidity of 65% during one week.
2.3.2. Thermal conductivity (Table 3)
Thermal conductivity measurements were carried out by the transient plane source method with Hot Disk TPS 2500S (Hot Disk AB, Gothenburg, Sweden). It consists of an electrically conducting pattern in the shape of a double spiral inserted between two identical pieces of sample. The conductivity was calculated by the Hot Disk 6.1 software with measurements parameters of 10 mW power and 40–80 s of measurement time. The sensor C5501 with radius 6.403 mm was used.