When emulsions are left at rest or gently stirred, the coalescence process continues until the surface concentration reaches the critical value of around 3.5 mg/m 2 . This critical value of surface concentration is found to be independent of adsorption properties such as bulk concentration or nature of the solvent (Pauchard and Roy 2014; Rapid contractions and expansion of asphaltene-laden interfaces using the pendant drop as Langmuir trough experiment is performed to simulate the rapid increase and decrease in interfacial asphaltene concentration that occurs during coalescence events . In contraction experiments of droplets aged in asphaltene solutions, contraction curves follow the Langmuir EOS for surface pressure values up to 21 mN/m (Figure ). Beyond that, the contraction curves deviate from Langmuir EOS consistently at a surface pressure value ∼21 mN/m, which corresponds to a surface coverage of approximately 80%. At this stage the droplet does not follow the shape of the Laplace-Young equation, indicating solid-like surface behavior. On further contraction wrinkles appear. Wrinkles observed are, however, not stable and disappear after a few minutes. This behavior is interpreted to be due to a transition to a glassy interface on contraction past the packing limit (~85% as determined in previous study by , followed by slow desorption. Figure shows the surface pressure versus interfacial coverage for 4 loops of expansion and contraction hysteresis experiments. The results show that there does not appear to be aging /crosslinking /gelation at the interface as all the curves fall onto the same Langmuir EOS for surface pressure value ∼21 mN/m.