How to striaghten Natural hair with no heat?

[Sweet_Ambrosia]

Ponytail Rollersetting gets my hair pretty straight w/o heat.

 

[FlowerHair]

I can get my hair semi-straight by putting my freshly washed and combed hair in a tight bun until it dries. The downside is that it takes forever to dry in a bun erplexed so I alternate with a loose twist at night.
It all depends on your hair texture, I think.