Ok. My marquis is already over a year old, so I would assume it would be less potent. I had tested a pill that turned dark purple, but not really black. I figured that was a good sign. I wanted to see what would happen with aspirin. It is supposed to turn a deep red. The only type of aspirin I had was ecotrin 81mg. I didnt see any color change at all though. It was not pure aspirin, there was a bunch of filler which might have given me this result. So is it time to buy a new marquis testing kit?