Paper recycling has become more common these days, but not all paper is the same. One problem that paper-recycling plants have been facing lately are old photographs being tossed into the mix with office paper and magazines. Unfortunately, photographs contain a thin layer of polythene, which is the coating on top that gives you a gloss or matte finish. This can clog paper-recycling machines. When in doubt, it's better to toss rather than try to recycle.