That could be dangerous (fire hazard). I wouldn't put cardboard no matter what it was covered with anywhere near a HID bulb. Buy a cheap 400w set up on ebay, if you watch auctions you can get an entire set up including ballast, reflector, bulb, and yo yos for about $120. Your first harvest will cover that easy.I gess you could always get some cardboard and mylar if your abit tight on your budget, get some cardboard and stick the mylar to one side bend the cardboard in the middle and you got something thats better than not having one yeah, scunk
what he said, visit the newbie central and read "how to grow marijuana" it eliminates duplicate posts and questions that have been answered ad nauseum.I think you might want to read a little more about growing. Just my2 cents