How can I copyright/protect my printed images?

[ABrownPhoto]

I am going to be shooting a private party on Friday the 3rd and the host wants me to print the images then and there for the people. I'll use my Epson R260 and a borrowed Epson R220 to make the 4x6 prints. It is a sweet 18 birthday party with a BUNCH of girls from 8pm to 2am and I will be making $100/hr + the cost of GAS and my supplies (ink and paper). I know my rate is cheap so no need to inform me :p

Anywhoo, how will I be able to stamp the back of the photos with a "DO NOT DUPLICATE" kind of thing so everyone will have to come back to ME for additional copies? I COULD buy a stamp from Office Depot or similar and customize it, which would work for the party since the images will print 1 by 1, but for future usage, If i have an order of 500+ images, it would take weeks to stamp them 1-by-1.

Any help would be awesome and much appreciated!

CLIFF NOTES: What is the best way to tag the back of my prints with a "DO NOT DUPLICATE ~ ABROWNPHOTO.COM" message so people cannot make copies at Kinkos or places like that?

[chris_m_atl]

I'm unfamiliar with those printers, but is there not a way to print directly on the back of the photo paper? One run to print your copyright -->flip the page --> and another run to print the images...

[ABrownPhoto]

I'm unfamiliar with those printers, but is there not a way to print directly on the back of the photo paper? One run to print your copyright -->flip the page --> and another run to print the images...I was thinking about that but am unsure if the backside of the photo paper is ink friendly. I'll have to experiment i guess :D

thanks

[ssim]

I have made small labels that go on the back of the shots. I had mine printed for me but prior to this I had done this with Avery labels and run them through my printer. I am always cautious about stamping the back of images. I had a bad experience where I did wait quite awhile before piling them up and I still had ink transfer to the front of the image from the previous print.