This is a kitchen activity and requires the use of a blender (or you can boilthe cabbage instead), red (purple) cabbage and assorted foods and liquids. Warning: it is a bit messy and smelly! This one is fun - let the kids help!

Go to: (opens in a new window Google)
Type in Timothy Craddock Hands-on Experiments
Click on the first result: Hands-on Experiments to Test for Acid Mine Drainage
Click on or scroll down to find Activity #1 - "Making your own litmus paper".
Read about the pH scale.
Skip "What to do" - cabbage leaves rubbed on the white paper does NOT work very well. Instead, do "More things to do" - here are detailed instructions:

Cut two or three 2-inch chunks off of a red (purple) cabbage.
Place them in a blender with a few tablespoons of water (if you don't add water the leaves won't blend). If you don't have a blender, boil a few of the cabbage leaves in a small amount of water which you can then use as your pH indicator.
Blend the cabbage chunks until liquid.
Using a strainer or cheesecloth, strain the blended cabbage into a glass measuring cup (any cup will do; the purple juice may stain plastic, however).
I ended up with about 1/3 cup of the purple liquid, which is more than enough to do the exercise. This is your "litmus paper" (litmus liquid, actually). It turns out that the pigments in red cabbage are good indicators of pH!
Pour about ¼-1/2 inch of the test substance (such as lemon juice; see below) into a small glass such as a shot glass (I have several if you need to borrow one - ha!). Then add a few drops (3-5) of the purple liquid to the shot glass and record the color change.
If the test substance stays bluish purple after you've added the purple litmus liquid, the pH is at or near neutral (7.0)
If the substance turns pink,it's acidic. The brighter the pink, the lower the pH.
If the substance turns bluish-green, it's somewhat basic, and if it turns green,it's very basic.

Test the 8 substances indicated below and determine if they are a strong acid (bright pink), weak acid (pinkish purple), neutral (bluish purple), weak base (bluish-green), or strong base (green). Record your results.

Ammonia (or a glass cleaner like Windex, or bleach)
Vinegar
Lemon, lime or orange juice
Beer, white wine or soda (clear color, if possible)
Liquid laundry detergent or hand soap (clear works best)
Tap or well water
Lake, pond or puddle water (or urine if needed!)
Egg white

Feel free to test other liquids such as urine, saliva, etc...!
Rank the above substances in order of pH, starting with the most acidic. Be sure to indicate what color the substance changed to.

Don't worry about being perfect in your pH rankings - just use your best judgment. Some of the items will be obviously very acidic or basic, while others will produce more subtle results.