zlacker

My regular shoes have round laces, I'd guess they are nylon, some kind of synthetic fiber. Sort of slippery. Never have a problem with them coming untied if I pull the knot tight though. I don't double knot.

Maybe I did the Ian knot wrong. Don't have a problem with the knot I use so not investigating further.

>>throwa+(OP)
> My regular shoes have round laces,

I don't know why anybody makes round laces, especially out of a material that slips.

I have a pair of dress shoes that came with round laces. Even with a "correct" knot, even with double-knotting, they always came undone. I replaced the laces with standard flat laces. They might not look as good, but they look better than having to re-tie them every 30 minutes.