What you will need.
You will need photosensitive paper, the same stuff that's used in a darkroom. Black & white or color. Resin coated or fibre. It doesn't matter. Personally I prefer resin coated because the fibre paper tends to curl and makes some strange lines on the paper. And I like B&W better because it starts off as a white piece of paper and you never know what color you're going to get.
You will also need either a contact printer or a heavy piece of glass. This is used to keep the object pressed flat against the paper.
Lastly, you will need a subject. I use mainly plants and fruit. The juices from these also make a color shift on the paper.
Prepare & Compose.
Make sure your glass is clean and there is no dust, hair or smudges; these will show up on your paper. However, if you missed something it's not a big deal, you can just remove them in Photoshop. Place you subject(s) on the glass and arrange however you like. Place your paper on the subect and glass with the photosensitive side touch ing the subject. Do this step quickly because the light will immediately begin to expose the paper. If you have a contact printer, place the back on and secure it. If you are just using glass quickly and carefully flip the arrangement so as not to disturb your composition. Place your contact printer somewhere where it will recieve a moderate amount of light. If you place it outside your plant might start to sweat and water will form on the glass. This is normal and it will most likely form a sort of aura like in the picture below.
Watch & Wait.
You will be able to see the paper start to change color right away. The longer you leave it in the light the more contrast and detail you will see when you remove the subject. Although after a certain point you wont notice much change.
How-To: Make a Lumen Print.
Scan, Store & Play.
Remove your print and scan it on a flat bed scanner. I scan mine at 600ppi as a TIFF, but you don't have to use those options it really depends on what you want to do with it. When I'm finished scanning I place it back into one of the dark bags that comes with the paper. Now it's time to have some fun! Open your scanned lumen in Photoshop and go wild. I usually play with curves and contrast. I also invert the lumen to get the positive. This is also when you can clean up any specks of dirt of hair you might have missed while cleaning the glass.
