It is convenient to ship plasmids dried on a piece of filter paper. What else is needed is just an envelope that can be shipped at the ambient temperature. However, not every kind of filter paper works alike. The 3MM paper is commonly used and works fine. We learned from the real-life troubleshooting experience that some other paper for sure can't work, such as the Whatman™ Grade 589/3 quantitative filter paper. When tested in parallel, we got a black-or-white result in our case: Plasmids could be efficiently eluted from the 3MM paper and tons of colonies were obtained while no colonies at all were obtained with the Grade 589/3 paper. What is the reason for it? We don't know for sure, but when no plasmids can be recovered to generate colonies, sometimes the filter paper is to be blamed. Using the right PAPER could do the trick!