WAPI (Water Pasteurization Indicator)

The WAPI (Water Pasteurization Indicator) is a reusable, inexpensive thermometer employing a plug of soybean wax which melts at 68˚C, just above the 65˚C or 149˚F pasteurization temperature for water or milk, at which point all disease-causing organisms (bacteria, viruses, and parasites) are killed.

Since the water is not heated all the way to boiling, and merely reaches the pasteurization temperature, time is saved and less fuel is consumed.

The hydrogenated soybean oil called Myverol 18-06 K (a food-grade emulsifier powdered wax) is encased in a small clear plastic tube, weighted with a metal washer. Fishing line or wire suspends the WAPI toward the bottom of the water container (where the water is coolest). The WAPI is oriented with the wax plug at its top, but after melting the wax flows to the bottom part. Then the user can remove the WAPI by the string or wire without contaminating the clean water with the fingers.

• Solar Cookers World Network Wiki article on the WAPI
• Buying vs making your own WAPI
• WAPIs for sale from Solar Cookers International.
• How to make WAPIs
• Making a WAPI from a ballpoint pen