Milk, buttermilk and sour cream are appealing dairy foods, but get them on your carpet, and you'll experience an attitude shift. Not only do milk and milk products seep into carpet fibres and padding, but left untreated, the soured milk creates an undeniably unpleasant -- and lasting -- odour. Removing the visible stain is not the most difficult of tasks. Getting the sour milk odour out of carpeting, however, takes a little more time and effort.
Blot the liquid. As soon as you notice a spill, blot up the liquid with paper towels or a soft, absorbent cloth. You may need more than one paper towel to get the job done. Remove as much moisture as you can.
Wet the sponge. Dip your sponge in cold water, or run it under the tap. Get the sponge wet enough to enable you to transfer water to the stain. You can use an ordinary, household sponge for this step.
Sponge down the stain. Press down on the stained area with the sponge until you transfer water to the stain.
Blot again with a paper towel. Blot up the water from the sponge. Then sponge and blot again three to four times. Your goal is to be sure you have removed every trace of milk from the carpeting.
Sprinkle baking soda onto the stain. Use enough soda to cover the stained area completely.
Spray water onto the baking soda. Spray on just enough water for the baking soda to absorb it completely; you don't want to saturate the carpet with water. Leave the moistened baking soda on the stain overnight.
Remove the excess baking soda. Scrape off the baking soda that dried as it sat on top of the carpet overnight. Then, go over the area with your small brush to help loosen any soda particles that may have dried into the carpeting.
Vacuum the area. You will want, of course, to remove all traces of the baking soda. Be sure to vacuum the area around the stain as well.
Put lemon juice on the stain. If you can still see or smell the milk stain, apply lemon juice to the stain and leave it for 15 minutes or so.
Spray the stain again. Cover the lemon-juice-soaked stain with water, and blot up all liquid with a paper towel.
If the stain is in a high-traffic area, you may want to mark out the area to warn folks away, to allow the baking soda to dry overnight.
Chemical stain removers may act to bake a sour milk stain into your carpeting. According to Mrs. Clean USA, organic cleaners (such as baking soda and lemon juice) sidestep this risk.