How much the loop shape will turn out is decided before the wire has completed its turn. Whether a loop will be round or stretched, crooked or indented depends on the spot where you use the pliers, how your wrist is angled, and how much force is used. A beginner might think that a loop is such a small detail but it influences how a linked bead will hang and how your earring will drop down. Also, a neat loop can affect whether the finished jewelry piece will be attractive.
Since round nose pliers have jaws that are wider near the handles than near the nose, you can make different sized loops. For example, when you place the wire at the nose of the pliers, the circle that forms will be smaller than the circle that forms when the wire is placed near the handle. It is difficult to place a loop in exactly the same spot on the pliers to get it right, because just a small shift of your grip can make the loop larger or smaller.
It is a good idea to use scrap wire before you use a bead or a specific finding. Place a tiny guide mark on one jaw of your round-nose pliers by using a small piece of masking tape or some kind of removable marker. Now, when you use the scrap wire, you can hold it at the same spot as the guide mark. Gently grip the wire there and roll it around the pliers, being calm and smooth. It isn’t necessary to pinch so hard that the wire makes a perfect circle; you just need to use the pliers to help you bend the wire. You hold the wire with a firm grip, and the pliers help to guide the curve. When you have made a loop, it is helpful to leave it on your work table and place other loops nearby so that you can compare the circles that form.
Often, a loop is out of round because you used two parts of the plier jaw when you bent the wire. You may have begun to wrap the wire near the top of the pliers and finished it near the bottom. If that happens, your loop will not be round, but more like an oval that is tilted. You can also have a problem by bending too closely the loop neck, since this can make the bead sit at an awkward angle. Before you consider whether it was the bead that was out of focus, be sure you were placing your wire on a consistent spot on the round nose pliers. The very same wire can react differently if you change the position at the pliers.
Also, consider how much force is needed with the pliers. Soft craft wire can be easily dented by round nose pliers because you squeezed with a lot of pressure. Plated wire can lose its sheen if you keep grabbing at the same place over and over. You need less pressure than that, especially when you practice with scrap wire. This is particularly important when you work on very small linkages in an earring or necklace design. You need to keep your wire where it needs to be without trying to squash the loop into a circle. You can change the placement a bit if the wire slips away, which doesn’t mean you have to crush the loop.
You can do your own quality control before you finish a jewelry piece. Take a loop and hang it from a jump ring or ear wire and let it dangle. See if the bead drops the way that you want it to or if it falls sideways. Check also whether the bead sits in the middle or if it hangs off to the side. Notice if the gap at the loop neck and loop opening has a place where the chain, fabric or the finding can get caught on something. If a loop that looks neat on your work bench hangs oddly when it dangles off an earring, the problem isn’t that you can’t make a loop, but that your loop is crooked or out of line with the wire.
It is by repeating the same loop-making motion that you start to make cleaner loops and that your fingers start to recognize the motion. Use more than one scrap wire, and save a few that you don’t like, so that you can study them later to notice how one loop has a plier mark, or another one is too open, or a third is too high above the bead. By looking at your samples you can tell your next loop-making experiment to do better. You don’t have to produce a perfect jewelry piece for every attempt; you only have to learn that you need to use more or less pressure, keep your wire steady in a certain position, or slow down when the wire is moving.