I never did get a recent sample. I also did say that this might happen, so asked for direct shipping, since you claim it MUST be contamination. Yet here we sit, several years alter after my first incident, with many other users reporting issues. There MUST be something to this issue. This is not a matter of placing blame on you guys directly...rather, an investigation to see what the common factor is here that made for all of these users, myself included many years ago, having the exact same problem from a sampled product. Since it was samples, many of us consider this "beta" testing, and as such, accept that there are risks involved. In an effort to minimize this risk, users with the problem, are more than likely not going to be happy with the response "you contaminated your sample", when for some users, they took the package out of the envelope, removed the lid, and applied the paste, only to be met with problems later on. How is it that we ALL manage to contaminate our IC diamond, and are met with similar issues? As to staining, I do have a solution, and that is to use Artic Silver Cleaning Solution. This two-part cleaner first emulsifies TIM and leaves an oily layer that forces particles to raise off the surface being cleaned. A second chemical, that in the least contains citric acid, removes the left over oil. It cleans far better that just Isopropyl, even 99.999%(which is what I used to use until I tried this product.). I wonder if this cleaner will help with "staining" issues? I can agree that surface contamination is very possible, since dust is floating in near everyone's home, and nearly no-one assembles their system in a clean room. If contamination is really such an issue, perhaps this product wasn't meant for home use. I know, for a fact, I followed direction explicitly, but was met with issues, your claim of not being possible or not. I will never back down form this, because that's what happened. I got my tube, opened the envelope, cleaned the heatsink and GPU with isopropyl using a soft cotton cloth, opened the tube, applied the paste, installed the heatsink, installed the GPU, and it didn't work. I hate to say I told you so...but I told ya this would happen, and that was why I wanted you to send me a sample directly, which you refused. That definitely didn't build any confidence in your products on my end. And I bet all these users here reporting issues will not recommend your product, either. For you to just say "it's not our fault"...well...that's not nice to hear. Just saying.