Hi I've just got a set of these tubes, and I have a small problem with them. I was practicing using them (with water in the light, no film) and when using the suggested 60ml into the tube cap it comes up the thread some ways. I was suspicious of this and sure enough, it spills out the sides when placing the top onto the cap (with cap inverted as a cup and at bottom as described). I estimate that I loose about 5ml. Is this normal?