Place the full side of your warped reel-to-reel tape on your tape deck's left reel, and place the empty side of the tape on the right reel. Turn on your tape deck, and fast forward the tape until all tape from the left reel is transferred to the right reel.
Remove the tape from the tape deck, and place it on a cookie sheet. Preheat your baking oven at 140 degrees. Bake the tape for about 4 hours. Flip the tape over every 30 minutes so each side of the tape bakes evenly. Baking your tape, a tape-restoration technique used by recording engineers, irons out the warps and creases in your tape.
Remove the tape from the oven, and allow it to cool down for about an hour before testing the tape on your reel-to-reel deck.