interfacing.

[crawl27.livejournal.com]

so i dont' really know much about interfacing, but i've been using a really stiff interfacing while making purses and its been making my fabric wrinkle up a bit. is this because the interfacing is too stiff for the fabric? or is my iron on too hot?

what setting should i have my iron on? (mine has settings like wool, cotton, linen etc)