It is possible to obtain big, loose curls in the hair if the only curling tool you have to work with is a small barrel curling iron. The technique used to curl the hair can be altered by using large sections to create big curls.
The trick is to section off parts of the hair in wide strips and use a comb to lightly tease near the root of each piece of hair just a little. Then, spray the hair lightly with a volumizing hair spray to hold the curl in place. Before starting, make sure to find a setting that is not too hot, as this can damage your hair. Then, begin taking each section of the hair and wrapping it around the curling wand, being sure not to catch the edges in the curling wand. When using a curling iron that does not have a clamp, be sure to wear a heat protection glove on the hand that will be handling the hair. Remember to wrap wide strips of hair around the wand and make sure it is not wrapped too tightly. Otherwise, the curls will not be big and loose. Allow the hair to set on the wand for about 5 to 10 seconds and then release the curl. As you go, spray the curls lightly with setting spray. If you are doing it correctly, the curls should have the shape of a large "S." When you have finished with the whole head, allow the hair to cool for a few minutes, then bend over at the waist and run your fingers through the hair to loosen up the curls. When you flip your head up, you should have a head full of big, loose curls. Style any out of place pieces and spray all over with a flexible hold hairspray and you should be all set!