A simple method of agitating cans to cause rapid heat penetration during thermal processing in retorts has been developed. Cans are oscillated in a circular path in such a way that can orientation remains fixed. The effectiveness of this method was tested with bentonite mixtures in 603 × 700 cans with different oscillating radii, headspaces, viscosities and can orientations. Heating time of 5% bentonite mixture was reduced from 360 min to less than 10 min. Although comparable heating rates were achieved with end-overend rotation, circular oscillation required only a 1/2–3/4 in. radius and caused lower inertia forces. These features make this method readily adaptable to conventional retort systems.