Cross processing (sometimes abbreviated to X-pro) is the procedure of deliberately processing film in a chemicals intended for a different type of film. The two main methods of cross processing involve developing a slide film in C41, or colour negative film in E6. The result is an unpredictable range of colours, and is often used by Lomographers.
Unable to acquire any tungsten-balanced film, I made use of a solid-blue filter when shooting a roll of Fuji Velvia 100. Having recently acquired some outdated (but sealed) C41 chemicals, I decided to cross-process the film at home. The recommended development time was 3:15 minutes, however because colour developer B had expired, I ignored the instructions and developed it for 5 minutes instead. After the blix bath, I removed the lid to find...images! They were around 2 stops too thin, however good enough to scan.
Canon EOS 600 loaded with Fuji Velvia 100. 28-135 with blue filter. Scanned with a Plustek OpticFilm 7400 at 3600dpi. I had to use heavy and intensive software-based dust removal due to insoluble particulates in the developer solution. On images where this was problematic, I layered an un-treated scan to ‘paint-back’ the detail. Otherwise, photoshop work was pretty minimal.