How do you get mail sent without it being bent?

Question

I've never mailed something before...

But I'm supposed to be mailing someone an original watercolor piece to someone across state and I don't want this to bend--it'll ruin the quality.

Do you pay extra? Or do you send it between cardboard? How? :< Thanks x_x;;

(BEST ANSWER WILL BE REWARDED!)

Answer 1

Pack it very carefully between two heavy sheets of corrugated cardboard or coreplast (corrugated plastic).  Mark it in very large letters FRAGILE and DO NOT BEND.  I pack photographs (8X10 and 11X14) this way for shipping.

You may also want to ask at the post office - they may have better suggestions than this.