The accuracy and precision of current ice nuclei (IN) instruments is reported and progress made toward addressing apparent shortfalls in past ice nuclei measurements is studied. Most new IN instruments can measure at controlled conditions below water saturation and, in some cases, well below -40°C. The UF FRIDGE and the Tel Aviv University (TAU) FRIDGE have showed much lower concentrations of ice nuclei than any of the CFDC instruments. A postanalysis of the measurements has revealed that the petroleum jelly used to increase thermal contact between the collection filter and the cooling stage became mobile at the low pressure operational conditions and condensed on the ice nuclei, leading to a deactivation effect. The longer evaporation section of the ZINC instrument permits extension of measurements to a higher water supersaturation bound before water droplets begin to survive through to the optical detector.