I boil my cartos. I get MOST cleaned. Certain juices that are strong or dark or thick juices I can't get out completely. If the carto has burnt filling I toss it because that can't be undone. Some cartos that I don't think are gonna be able to be cleaned well because of the kind of juice I put in them I try anyways and am pleasantly surprised. Others, no. If I see the filling looks bad I toss. Sometimes I will get a carto where the filling has changed and it's hardened and I toss. But most of my cartos I have been able to clean out well. I boil 2-3 times. I have a metal drainer that sits in the pot and keeps the cartos from being on the bottom of the pot, to protect the atomizer inside. Then when done I rinse well (and in between boilings too when I add new clean water) and then I blow them out VERY well and dry in the oven on a cookie sheet, mouth piece end down so the atomizer in the battery end is protected. I dry for 40 mins at 175 degrees and usually let sit overnight as well as I usually boil in the evening, sometimes right along side dinner lol (but not TOO close to dinner lol). Oh and since I use cartos with different colored wrappings on them I also wipe off the wrappings before I put the cartos in the oven so there are no juice spots on them.