Supplies
National Geographic magazines
Thick layer of newspapers
Citri Solv It is a degreaser and solvent available at Canadian Tire Stores. It is a liquid and smells like oranges.
A brush 1 to 2 inches wide to spread the Citri Solv on the magazine pages.
Method
Go through the NG mags and choose some pages with colours you like
Place a page on the newspapers.Poke the smallest hole possible in the Citri Solve seal.
I find that applying the solvent to the brush gives better control and less waste.
Just press the side of your brush gently to the chosen page.Carefully apply the solvent to the brush. Don’t flood the page.
Place the next page face up on top of treated page.KEEP ADDING PAGES AND TREATING WITH CITRI SOLV.
WHEN FINISHED, PRESS PAGES FIRMLY TOGETHER FROM THE TOP. NOW,WAIT.CHECK AFTER AN HOUR. IF YOU LIKE THE RESULT,PUT ASIDE TO DRY. IF TOO MUCH ORIGINAL PICTURE IS SHOWING FOR YOUR TASTE,ADD MORE SOLVENT AND WAIT SOME MORE.
Examples
Deestamper's Weblog 
what a fascinating art technique