A novel apparatus was developed to monitor bubble-bitumen droplet attachment process and to determine induction time required for the attachment. This unique apparatus is capable of generating individual hydrogen bubbles with a desired size larger than 10 mum. Once a hydrogen bubble of a desired diameter is produced, it is released to contact a suspended bitumen droplet. The entire bubble sliding and attachment process is recorded with a high-speed digital imaging system for subsequent playback and analysis. A number of factors that affect bitumen flotation were studied with this technique, including process temperature, bubble size and aqueous phase chemistry. The induction time, which is a measure of the time required to form a stable, three-phase contact between a gas bubble and a particle or droplet in an aqueous medium, is used to quantify the attachment process. The induction time of hydrogen bubble-bitumen droplet attachment was measured as a function of temperature, bubble size and rise velocity, and aqueous phase chemistry. The results showed that higher process temperature and smaller bubble size are favorable to bitumen flotation. It was found that the maximum (critical) bubble size required for effective bitumen flotation is highly dependent on dissolved air content and ionic composition in the aqueous phase. For experiments where the aqueous phase chemistry resembled that typically found in the oil sands industry, only very small bubbles were found to attach to the bitumen droplet. (C) 2003 Elsevier B.V. All rights reserved.