These data present volume estimates from images (using the solid of revolution method from the cross-sectional area) of clasts expanding during vesiculation at high temperature. The data also contain clast interior volume estimates without the dense rind around the clasts (formed by diffusive outgassing, and estimated through time),l which is is calculated in Matlab. The methods are provided in more detail in Weaver et al., 2022. These data contain sample measurements (surface area), total clast volume calculation (using solid of revolution from clast cross-sectional area), degassed skin area (using imerode in Matlab and the diffusion data provided in the table) and skin volume (solid of revolution from skin surface area), and core surface area and volume from the difference between total clast and skin volumes/skin area. All data are presented in Weaver et al., 2022 (https://doi.org/10.1016/j.jvolgeores.2022.107550), where further details of the methods can also be found. All data were collected and analysed at the University of Liverpool using clasts from Hrafntinnuhryggur, Iceland. The geographical location of the samples collected is of no relevance to this study, as the samples were selected for their physical attributes. All data were collected and analysed throughout 2021 and 2022. Volcanic glass cylinders of different starting sizes were placed in a furnace at high temperature (1006 oC). Two furnaces were used, either a tube furnace with open ends to allow imaging of the sample silhouette, or a box furnace with a sapphire window to allow imaging of the sample as vesiculation takes place. Cross-sectional areas are then converted to volumes using solid of revolution as vesiculation is isotropic. Diffusion modelling is used to quantify the development of the fully degassed rind around the sample and used to estimate the rind volume through imerode in Matlab and solid of revolution. Total clast, core and rind volumes are thus able to be retrieved. As magmas approach the surface of the Earth, volatile saturation in the melt decreases, which results in volatile exsolution in vesicles (vesiculation) and outgassing. The interplay between the amount of vesicles trapped in the melt and those that diffusively outgas from the surface is dependent on the volume to surface area ratio. Understanding the kinetics of outgassing and vesiculation is key to understand pressure build-up in magmatic conduits and effusive-explosive transitions at volcanoes.