Optiphen Plus Optiphen PLUS is a Natural Preservative. WHY DO YOU NEED THIS? You can use this in products with water in it and helps to protect against bacteria, mold growth and even yeast! This preservative is great for making lotions, creams, shampoo, scrubs and other personal care items.  HOW TO USE  The recommended usage is 0.75 - 1.5% of your product or 7-9 drops per pound of solution This chart shows some examples of how much preservative to use. You can take the volume of your product and check either how many drops to use or how many ounces to use, whichever is easier for you! Ounces of product Drops of Optiphen  Ounces of Optiphen  16 oz/ 1 pound 7-9 drops  0.12- 0.24 oz 32 oz/ 2 pounds 14-18 drops  0.24- 0.48 oz 64 oz/ 3 pounds  21-27 drops  0.48- 0.96 oz 128 oz/ 4 pounds  28-36 drops  0.96- 1.92 oz