Solid state picosecond laser sources are reliable tools for micro-ablation in industrial applications. Double-pulse ablation with picosecond pulses is a promising way to maximize the efficiency of the ablation due to plasma and thermal effects. Therefore, the increase of material ablation rates in Silicon and Aluminium using picoseconds double-pulses instead of single pulses was examined. The experiments were performed with pulse durations of 8.5 ps and a wavelength of 1064 nm. The double-pulses were generated using a Mach-Zehnder interferometer setup to be flexible in choosing the delay between the two pulses from a few picoseconds up to several nanoseconds. We show that the progress of ablation rate per pulse is highly influenced by the inter pulse separation and reaches global maxima depending on material properties. Furthermore we present first results of the investigations of ablation shape and surface roughness.