I am not sure how to do it but i think it is called cornelli lace.
cakeconfections is right...it sounds like cornelli lace. I'v done this a couple times. I used a 3 tip but you can use a smaller size if you want it more delicate. Then you pipe one continous line that never crosses or touches itself...looks like your making loose R's or S'. Here a link to Wilton's directions
http://www.wilton.com/decorating/basic/lacework.cfm
There's two different kinds. The one that is easier because it is just squiggly and touches itself is called Sotas
http://www.wilton.com/decorating/basic/sotas.cfm
The one that is more detailed, being one continuous line that does not touch itself, does not cross over itself, and does not break is called cornelli
http://www.wilton.com/decorating/basic/lacework.cfm
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