coke absorbs moisture from the air... when you dump it out of the bag its moist and tends to stick together.. thats why razors are the best for coke.. if you use a card it wont be thin enough to cut it into a nice snortable powder.. thats why if you cut coke even with a razoer and wait a minute or two to snort it.. the coke will cake up and need to be cut again. for other things a razor would be annoying to use and take too long to cut up... a card is best for all powders except coke.