Abstract: A novel temperature indicator having a cover layer and including a backing strip with an embossed well stamped therein is provided (in the alternative, the cover layer may be embossed) to form a pocket. The well may contain a matrix carrier which is impregnated with a thermally responsive fusible chemical. The bottom of the well is painted a bright color. If employed, the impregnated matrix is placed over and substantially covers the colored bottom of the well. The top of the well is covered by a transparent film. At a temperature below a predetermined level, the colored bottom of the well is substantially invisible due to the impregnated matrix being opaque, and at temperatures above such predetermined level, the colored bottom of the well is clearly visible due to the transparency of the impregnated matrix upon melting of the chemical. The matrix may be eliminated if the backing strip and/or cover layer is air permeable and if the chemical entirely fills the pocket.

Abstract: A time indicator which is substantially unaffected by variations in temperature. The indicator utilizes a silicone oil which is slowly absorbed onto and moves up a porous strip at a rate which is a function of time. One side of the strip is printed with an oil soluble ink, while the other side is unprinted. The printed side of the strip is laminated with polyethylene film to an unprinted strip. As the silicone oil moves up the strip, the oil contacts the ink causing a dye in the ink to migrate from the printed side to the unprinted side, thus providing a measurable color front moving up the strip. The oil is contained in a frangible ampul and a sponge with a small hole at the bottom is situated between the ampul and the strip. The indicator is substantially unaffected by normal variations in temperature and humidity.

Abstract: An indicator device for use as a time indicator or a time-temperature indicator. A container is provided for housing a frangible capsule and a porous carrier. A vapor generating chemical is enclosed in the capsule. A mixture, including a second chemical, a pH change responsive indicator, and a gel forming agent are impregnated in the porous carrier. The pH of the vapor is different from the second chemical. A gel is formed from the mixture and provides uniform dispersion of the second chemical and the indicator throughout the porous carrier, as well as provides an impedance to the vapor as it moves through the porous carrier. The device is thus useful as an elapsed time indicator for certain temperature ranges as well as a time-temperature indicator for wider temperature ranges.