Light Exposure Testing: Both formulas and packaging can be sensitive to the UV radiation. All products should be placed, in glass and the actual package, in the window and if its available a light box that has a broad-spectrum output. Place another glass jar completely covered with aluminum foil in the window to serve as a control. All too often we will see significant discoloration of the product and sometimes of the package also. This discoloration may be due to the fragrance or some other sensitive ingredient. Usually all that is needed is the addition of a UV absorber (e.g. 0.1% of benzophenone).