Methods are disclosed for identifying and treating oil sand ores having degraded bitumen. This can be done by considering the location from which the ore is mined or its history, or by microscopic examination of a bitumen froth made from the ore, or by near-infrared spectroscopy. Ore which contains degraded bitumen is treated with at least 0.05 wt/wt % alkaline material, preferably 0.1 wt./wt % of such alkaline material, in the water addition step of a hot or warm water extraction process for the making of bitumen froth, such as the Clark process.