The flowability of uncompacted marigold powder (ground petals), as determined by three different methods, decreased with higher moisture content over the range of 5.5-25.5% MC for samples of two different particle sizes and with addition of flow enhancer. Adding the flow enhancer tricalcium phosphate (TCP) decreased the repose angles, i.e., increased flowability for all treatments. From both static angle of repose and dynamic angle of repose tests, best flowability was found for 1-mm screen ground powder having 3% TCP; poorest flowability was for 6-mm screen ground powder having 0% TCP. Flowability of other treatments was intermediate. Using a newly developed method to measure flowability from gravity flow bins, higher frequency of vibration was required to initiate flow through an orifice for higher moisture content powders. For each powder, particle size, and amount of flow enhancer, there is an optimal range of orifice sizes to obtain the best test results. (C) 2002 Elsevier Science Ltd. All rights reserved.