In electric melters, the conversion heat is transferred through the foam layer at the cold-cap bottom. Understanding cold-cap foaming is thus important for enhancing the efficiency of both commercial and waste glass melters as well as for the development of advanced batch-to-glass conversion models. Observing foam behavior is still impossible "in situ," that is, directly, in glass melters. To investigate the feed foaming behavior in laboratory conditions, we employed the feed volume expansion test, evolved gas analysis, and thermogravimetry. Combining these techniques helps assess the cold-cap bottom temperature that directly influences the temperature gradient at the melt/cold-cap interface, and thus the rate of melting. We also discuss the behavior of cavities formed by coalescing primary foam bubbles and ascending secondary bubbles.