Refractometers are used at airtanker bases to determine the amount of salt in a sample of fire retardant. Because salt is the active ingredient in long-term fire retardants, a refractometer can give an idea of the effectiveness of the product, assuring that the quality is maintained in the field. In addition, the density of retardant is proportional to its salt content. Knowing the density of retardant is crucial to determining the weight of an airtanker after it has been loaded. Keeping an airtanker's weight within specified limits is critical for safe operation.

This project began as a proposal submitted by the Klamath Falls airtanker base manager to the Fire and Aviation Steering Committee of the Forest Service's Technology and Development Program. The proposal requested a survey of various types of refractometers to determine if any brands or types might be easier to use than the Reichert 10440 refractometer used at the Wildland Fire Chemical Systems laboratory and at most airtanker bases.

Refractometers are used in a wide variety of applications and industries. They can help determine the amount of solids in solutions ranging from fruit (to help determine ripeness and optimal harvest time), sauces (including soy and ketchup), antifreeze, washing fluids, beer, and wine.