A twin tube flash x‐ray unit is used to probe the density of expanding metal vapor produced in exploding wire experiments. Using an axial orientation for one of the tubes, details not seen in usual perpendicular pictures can be brought out. The developed x‐ray film is scanned by a microphotometer and the trace compared with a standard wedge exposed on the same film. The tracings are then reduced to obtain density as a function of radius. Typical results as applied to copper wire are included.