The age of fission neutrons to indium resonance energy (1.46 eV) was measured in mixtures of aluminum and water. Three different volume ratios of metal-to-water were investigated. The technique of a finite-plane fission source with essentially infinite-plane detectors was used previously at this laboratory to measure the age in pure water, mixtures of zirconium and water, and mixtures of iron and water. Similar to the iron-water mixtures, but in contrast to the zirconium water mixtures, the general curve of age vs metal-to-water ratio is not a linear function with aluminum-water mixtures. The curvature is caused by inelastic scattering in the iron and aluminum. For metal-to-water ratios of 0.25, 0.50, and 1.0, this experiment gave ages of 33.9 ± 0.6 cm2, 43.2 ± 0.8 cm2, and 59.6 ± 0.9 cm2, respectively.