I recently had a crack at a photography processing technique known as "Film Soup". The idea behind film soup is to intentionally damage your film before processing by bringing it into contact with a chemical such as alcohol or acidic substances such as cleaning products and then boiling it for the reaction to take effect on the film emulsion.
For the examples within this blog post I used a slide film and a regular colour negative film. After shooting them I unrolled them in a dark room and dabbed them with washing machine detergent. Afterwards I re-spooled them back in to the film canister and boiled them for 2 minutes in a pot of water. Once the film was fully dry I just processed them as normal. For this technique, you would definitely have to home process as Boots or Snappy Snaps wouldn't touch them with a barge pole!
It gave some quite interesting results, the colour negative had a consistent bright green splurge across the whole film while the slide film had more random psychedelic colours. I would like to give it another go using different chemicals at some point, but I have to wait while my current batch of processing chemicals are on their last leg as after this technique they are pretty much rendered useless.