At first when I tried these, I chose a white pen to write on a plastic cover notebook. I had trouble getting the ink to flow enough to get the effect I wanted. Then, I went back to the description for this item in Amazon and learned a few things; shake the pens before using them, etc. I then tried a pen on a slightly more porous surface and it worked just great. The key to these pens is to follow the directions! Next I tried writing on glass, and to my amazement, the pens worked just fine. Wish directions came with the pens, but ultimately I found what I needed to get the most from them, and now I can’t find enough things around my house to decorate with these pens!