Polyphosphates have been used very successfully for over forty years as corrosion inhibitors and sequestrants in public water systems. One question that comes up from time to time is "what causes the oil sheen on top of coffee?" If you use cream in your coffee it is even more pronounced. The question is whether or not his is phosphate.

The proper answer is that it is not phosphates, but the result of phosphate being in the water. One property that phosphates have is the ability to separate oil and other organic materials from water. This is the reason phosphates were used in laundry soap and disk washing liquids. We now use synthetic materials in these products to accomplish the same oil/water separation. All phosphates will separate oil from water. Some phosphates are better at doing this than others.

There are organic materials naturally found in water. When you brew coffee you are leaching organic coffee bean oils into the water. The stronger the coffee, the more oil in the water. Phosphate will remove a small portion of it. You won't see a difference in the taste, but you will see the coffee bean oil floating as an oil sheen on top.

We hope this explanation will be helpful in answering customers questions. Reassure them that his is a natural occurrence and that there is no problem.