How to shrink a potato chip bag- Preheat your oven to 350 degrees. Place an empty potato chip bag on a greased cookie sheet and place another cookie sheet on top. Place the pans into the oven and wait between 3-4 minutes. Check on your bag every minute or so to see how it's doing. If it starts to crackle too much, then it's time to take it out. Never put a bag in the over without closing it in the cookie sheets.