Here are a few different types to buy, What would you use for what kind of process?
http://www.eckraus.com/Page_1/PH110_____2844.html
http://www.eckraus.com/WIDE_RANGE_PH_PAPERS_(2/Page_1/PH115.html
http://www.eckraus.com/Page_1/PH110_____2844.html
http://www.eckraus.com/WIDE_RANGE_PH_PAPERS_(2/Page_1/PH115.html