A paper negative can be a gateway to many different types of interesting photographic effects. To make a paper negative, first choose an image that you would like to use for your paper negative. Once you have chosen your image, make sure it is printed on a photographic paper that does not have the companies logo printed on the back. Logos on the back of photographic paper will show up in the final print. Take this print and an unexposed peice of paper and place them both in a basin of water. Line up both prints with the emulsion side of the unexposed print facing the already exposed prints back and squeegee them together. Now, place the paper under an enlarger with the back of the already exposed print facing the top of the enlarger. Determine an exposure time (it will be very long probably in the 2-3 minute area) by making test prints. You will probably need to have your enlargers lense set at about f5.6 to achieve the best results. I have found that breaking up the time into 30 sec incriments will allow you more control in dodging and burning which is necessary with this process in a lot of cases.
Once you have created your paper negative you can use it to make a print from which will be vary grainy, and will look similar to infrared photography. You can also solarize the paper negative and turn the print made from it into a print that looks almost hand drawn. To do this take your paper negative and solarize it. Print a positive image from this, and you will be suprised what the resulting image will look like: a pencil drawing.
There are no limitations of the variety of creative applications that you can find for paper negatives. If you experiment with this tequnique make sure you document the exposures you use when printing, as they will help you the next time you go into the darkroom.