Measured tensile strengths for all five types of silica dust used in this study. All samples were compressed with a body weight of around 85 kg, and for each dust type half the samples were measured in air, the other half in a vacuum, either at room temperature or heated. The bigger and brighter markers are the mean of the smaller and more transparent markers. The dashed curves are the smallest ellipses (in lin-lin space) that include all measurements and are meant for visualization purposes only.