If I buy a dual voltage curling iron in the states will it work in Germany with a converter? I had heard that sometimes they do not heat up, or overheat.
If it's dual voltage, all you need is a plug adaptor to fit the outlet, not a converter.
Have used my dual voltage curling iron with just an adaptor plug in Holland, Belgium, Switzerland, France, Greece, and England with no problems at all. Don't imagine you would have any problems in Germany.
Same comment as Janis. Used my dual voltage (cheap, bought at Target) flat iron in Italy with an adapter, no problems, worked fine when I got home too.
Warning...it might make a bit of "noise" when you plug it in...it's just the change of current, and shouldn't affect the iron.
You might notice that the iron works just a bit hotter than in the US, so do watch it first few times you put it on your hair. if there is a cooler setting, you might try that first, then increase the temp.