Abstract: A process for the production of an indicator for monitoring the temperature of a cooled or deep-frozen product, such as packaged foodstuffs, pharmaceuticals and the like, is provided, which indicator shows that a predetermined critical temperature of the cooled or deep-frozen product has been exceeded. An easily applicable and economically made indicator is produced by casting a substance which is fluid or semifluid above the critical temperature into a specific geometrical shape and then cooling the substance below the critical temperature until it assumes a solid form. The critical temperature may in this connection lie above or below 0 degrees Centigrade.

Abstract: A guide member is slidably mounted on a rod, and a resilient seal bag around the rod is secured to the guide member. The rod is inserted in a heat conductive cylinder secured to the guide member, and wax is provided in the heat conductive cylinder. The seal bag has a base portion having an opening, and a bag portion, and is engaged with the rod only at the opening to form a gap between the bag portion and the rod. The gap is charged with lubricating oil. The pressure of the lubricating oil is built up to a value equivalent to the pressure of the wax, thereby holding the bag portion in a floating state. The rod is lifted by the pressure of the lubricating oil.

Abstract: The invention relates to a heat-shrinkable article that is at least partially coated with a temperature indicator. This temperature indicator is composed of an organic polymer having a suitable bonding agent, whereby the organic polymer is contained therein in a finely ground condition. As a result of this condition, the appearance of the agent is opaque and has a color corresponding to the degree of granulation and material constituent. When the melting point of the composition is reached, the material melts and becomes transparent or at least translucent. The color of the article shows through, so that this color change can be interpreted as a temperature indication.

Abstract: A device for monitoring temperature conditions in a frozen food storage space includes a rear panel and a parallel transparent plastic front wall having a peripheral skirt wall sealed to the panel front face. Laterally spaced projections intermediate the front wall top and bottom extend from the front toward the rear wall to delineate top and bottom cavity sections, one of which contains colored water. A suction cup is located on the panel rear face and indicia are formed on the panel front face registering with each cavity section. The device is located in the storage space until the water in the lower cavity section is frozen solid and is then inverted. The presence of water in the bottom cavity of the inverted device indicates the occurrence of a thawing condition in the storage space at the same time.

Abstract: An indicating device for indicating the time and temperature history of an object. The indicating device includes a reservoir containing an indicating material that liquefies at or above a predetermined temperature mounted on a base sheet, a removable barrier impervious to the indicating material interposed between the reservoir and a wick, wherein the wick is placed in contact with the reservoir after the barrier is removed to enable the migration of the indicating material along the wick at a controlled rate. The wick is constructed of generally hydrophobic materials so that the migration rate of the indicating materials along the wick is generally independent of changes in the ambient humidity.

Abstract: A guide member is slidably mounted on a rod, a resilient seal bag is provided around a first end portion of the rod and secured to the guide member, and a tubular sealing member is slidably mounted on a second end portion of the rod. The rod is inserted in a heat conductive cylinder secured to the guide member, and wax is provided in the heat conductive cylinder. The seal bag has a base portion and a bag portion, and is engaged with the rod only at the base portion to form a gap between the bag portion and the rod. The gap is charged with lubricating oil. The sealing member has a tubular body, a skirt portion, a closed head portion, and a plurality of annular grooves formed in an inner wall of the body. The base portion is secured to the guide member, and the head portion is engaged with an end of the second end portion of the rod.

Abstract: A method for monitoring frozen products and an indicator for temperature monitoring of the frozen products using one or several liquids with various melting temperatures; the liquids are encapsuled in cavities of an indicator and are frozen in certain geometric patterns. During the melting process these liquids lose their frozen shape. The cavities are at least partially elastic-deformable, and the liquid is forced into certain geometric patterns by means of mechanic deformation of the walls. The deformation of the walls is accomplished by application of a stamp which has been cooled.

Abstract: A temperature measuring device useful for measuring the temperature of urine samples is disclosed comprising a solid solution having incorporated therein a nucleating agent and an indicating dye system. The preferred solid solution is a mixture of ortho-chloronitrobenzene and ortho-bromonitrobenzene. The preferred dye systems are pinacyanol iodide and a mixture of bromcresol purple and ethyl red. A novel aspect of the thermometer is that it is adapted to indicate a predetermined temperature at an observable initiation of melt temperature which is about 0.3.degree. to about 1.9.degree. F. below the completion of melt temperature of the composition. The thermometer is a real time device.

Abstract: A limit sensing device for permanently indicating when a predetermined temperature limit has been reached in a fluid conduit, includes a housing mounted on the conduit in heat transmitting relation with the fluid and an indicator movable in the housing between a retracted position and an activated, non-resettable, extended position to provide a visual indication that the predetermined temperature limit has been reached. The indicator is biased outwardly towards the activated position and a retainer in the form of a separate and discrete annulus formed of fusible material normally secures the indicator in the retracted position within the housing against the force of a biasing spring until the predetermined temperature has been reached causing the retainer to melt or fuse and thereby release the indicator to move outwardly to the extended position providing a visual indication signaling that an overtemperature condition has been reached in the fluid conduit.

Abstract: A thermo-actuator has a steel rod, a guide member slidably mounted on the rod, a spool seal secured to the guide member, a heat conductive cylinder secured to the guide member, and wax pellets provided in the cylinder. The spool seal has a thin layer, so that the spool seal engages with the rod by a vacuum generated in the spool seal. The thickness of the spool seal is between 5% to 25% of the diameter of the steel rod.

Abstract: The cold indicator serves for the controlling of the cooling or freezing condition of foods, medicines and the like in an arrangement in which it is in heat conducting contact with the observed cooling or freezing goods; for the activating of the cold indicator, a mechanical force is utilized, which destroys a separating filament. The cold indicator consists of two opposite lying chambers having different volumes, between whcih a separating filament is arranged and there is a freezable fluid provided in the smaller chamber. Below the observed temperature, the fluid forms a cooling or freezing tablet, and activating the cold indicator is done by destroying the separating filament, and the table is brought into the larger chamber. If the cold indicator is thawed, then the cooling or freezing tablet irreversibly loses its shape and disperses in the larger chamber, which is visible from the outside and indicates that the cold indicator has been thawed.

Abstract: A device for indicating whether a rise in temperature above a predetermined value has occurred includes a support member, such as a label, on which a temperature-sensitive material is deposited. The material includes a large number of fracturable microcapsules containing a medium which changes from a solid state to a liquid state at the predetermined temperature value. The viscosity of the medium in its liquid state and the material of the support member are chosen such that the distance d.sub.1 by which the medium flows across the support member after the fracturing of the microcapsules so as to activate the device is indicative of the time between activation of the device and cooling of the device to below the predetermined temperature value. If the temperature is subsequently allowed to rise above the predetermined value, the medium will again assume its liquid state and will flow further across the support member, reaching a distance of, say, d.sub.

Abstract: The device comprises a transparent tube (1) wherein may slide freely a part (4) at the extremities of which are arranged two small magnetic masses (5,6). The tube (1), closed at both ends, forms a sealed tank wherein there is placed a phase changing material (7) which is either in a liquid state or in a solid state, according to the temperature to which it has been brought. At one of the ends of the tube (1) a cap (12) containing a removable magnet (9a) is fitted. A fixed magnet (11) is placed at the other end of the tube (1). The part (4) being initially placed on the side of the cap (12), the material (7) is solidified and the removable magnet (9a) is then removed. In the case of exceeding the melting temperature of the material (7), the part (4) attracted by the magnet (11) moves towards the corresponding end of the tube (1), thus making visible a colored ring (14).

Abstract: A method and devices for indication of temperature in frozen products are disclosed. The method involves placing an indicator having a cavity partly filled with a fluid in the freezing equipment. The fluid is frozen, and the indicator inverted. If the freezing equipment malfunctions and the freezer warms up, the fluid will melt and flow down, indicating a malfunction. The present invention includes paired indicators for use with frozen products that may be moved around in the freezing equipment; fluids in the two indicators are frozen in positions 180.degree. apart, so even if the indicator is inverted, it is still possible to get a valid temperature indication.

Abstract: A foodstuffs thawing detector device (1) comprised of a water-filled container (2) in which detection or marker means (5, 8 or 10) is maintained in a stable position by the freezing of the water in the said container (2), where the said detection means will reach a position other than the said stable position when the water in the container melts. A preferred embodiment consists in a container (2) having an interior cavity defined by frusto-pyramidal formations (3) oriented in opposed directions and joined at their smaller bases in line with a central transverse plane (4); preferably, the said formations shall have a square base, and even a truncated arrangement (6) or the like, and detection means comprised of a ball member (5 or 8) having a high specific weight, maintained on the said central transverse plane (4) by the freezing of the water.

Abstract: A monitor for detection of temperature and/or steam conditions indicative of sterilization. The monitor comprises means for creating a remotely detectable response upon interrogation by an electromagnetic field and means for changing the response upon exposure to a predetermined set of temperature and steam conditions. The remotely detectable response is preferably produced through the interaction of an electromagnetic interrogation field with magnetic components of the monitor, wherein the characteristic harmonic response generated by the magnetic components is either inhibited or enabled by the change in configuration of one or more elements of the detector. Sterilization conditions are detected through one or more compounds known to have melting points which are above the temperature used in the sterilization process. Melting of the chemical compound produces the change in configuration of the element or elements of the monitor.

Abstract: A temperature change indicator is described which is composed of an enzyme and a substrate for that enzyme suspended in a solid organic solvent or mixture of solvents as a support medium. The organic solvent or solvents are chosen so as to melt at a specific temperature or in a specific temperature range. When the temperature of the indicator is elevated above the chosen, or critical temperature, the solid organic solvent support will melt, and the enzymatic reaction will occur, producing a visually detectable product which is stable to further temperature variation.

Abstract: Indicating device suitable for visibly indicating conditions such as the application of force or pressure or the exposure to a critical temperature. The device includes a porous pad containing an indicating dyed chemical, a wick maintained in spaced relation to the pad and a snap action activating means. The activating means forces the wick into contact with the pad and dyed chemical migration provides visible indication of the application of force or pressure. The indicating dyed chemical may be frozen and the activating means engaged. Upon reaching a critical temperature the frozen chemical melts allowing dye migration into the wick and a visible indication of exposure to the critical temperature.

Abstract: Temperature is measured by launching pulses of light into an elongate optical fibre and determining the temperature at positions along the fibre from the intensity of light scattered at those positions. The input pulses can have either the same or two different wavelengths, and the scattered light can be either Raman or Brillouin scattered and either forward scattered or backscattered. One position along the fibre can be maintained at a known temperature in order to provide a reference for other calculations. In particular embodiments the temperature is derived from the ratio between the intensities at two anti-Stokes wavenumber shifts or between an anti-Stokes scattered and a Rayleigh scattered intensity measurement. Otherwise the intensities of Stokes and anti-Stokes shifted Brillouin back scattered light can be used to derive the temperature.

Abstract: A poultry or meat cooking timer has a hollow barrel with an open top slidably receiving a stem with an inner end immersed in a fusible holding material in the barrel to normally hold the stem within the barrel against the force of a spring in the barrel urging the stem outwardly therefrom. The stem has an integral tapered flange thereabout that is force fitted through an inner barrel ridge near the top of the barrel bore and the stem has a large top with a substantially flat surface for engaging a barrel flange for positively sealing the stem and barrel in normal retracted stem position to prevent intrusion of foreign substances into the barrel bore prior to stem release by the fusible material at a predetermined temperature.

Abstract: A simple and inexpensive instrument for measuring electric current that may be mounted on existing current-carrying conductors to provide a ready visible indication of the current flowing through the conductor. The instrument comprises an outer transparent tube mounted coaxially with the current-carrying conductor, a number of O-rings mounted within the tube and spaced along the length of the tube to form different compartments along the instrument, and a number of differently colored tubular indicators respectively forming the inner walls for the compartments, with each compartment being filled with a material, such as paraffin wax, which melts at a different temperature from the material in the other compartments, to become transparent and reveal the corresponding colored inner indicator, when the current in the conductor heats the conductor to a particular temperature.

Abstract: A simple and inexpensive water temperature sensor that may be mounted on existing water faucets or showers to provide a ready visible indication of the temperature of the water flowing through the faucet or shower. The temperature sensor comprises an outer transparent tube mounted coaxially with the pipe leading to the faucet or shower head, a number of O-rings mounted within the tube and spaced along the length of the tube to form different compartments along the sensor, and a number of differently colored tubular members respectively forming a second wall for the compartments, with each compartment being filled with a material, such as paraffin wax, with the material in each compartment melting at a different temperature from the material in the other compartments, to become transparent and reveal the corresponding colored inner tubular member, when the water flowing to the faucet or shower has a particular temperature.

Abstract: This invention relates to a temperature control indicator unit comprising a substrate having supported thereon (a) microcapsules enclosing a hydrophobic organic compound possessing an arbitrarily selected melting point, (b) a methine dye and (c) an oxidizing material. More particularly, a unit made by combining an irreversibly color-developing methine dye and an oxidizing material with microcapsules enclosing a hydrophobic organic compound possessing a predetermined melting point and supporting them on a substrate is used for temperature control purposes. A suitable measure is taken, preferably at or below the desired control temperature, to break at least a part of the microcapsules of the unit and thereby produce fissures or the like in the microcapsule membrane. Then, the unit is stored or transported together with an article to be placed under temperature control.

Abstract: An indicator comprising azo dye(s), epoxy compound(s) and a separating membrane can be utilized for detection of the completion of thermal sterilization treatment in the medical field and also for thermal inspection in such various fields as testing, instrumentation and the like. The indicator can be used also for detection of the completion of alkylene oxide gas sterilization treatment by ethylene oxide gas or the like.

Abstract: A method of monitoring if a stored product has exceeded a predetermined temperature using an assembly, which comprises coated onto a carrier a gelatin layer containing an acidic reactant, color former and an encapsulated non-aqueous solvent.

Abstract: A temperature sensor is provided comprising a conductor having a low-melting-point, a fibrous insulating layer adjacent the low-melting-point conductor and separating it from a second conductor. An oscillator applying a pulse signal to the sensor and a receiver receiving the pulse signal through the sensor can detect changes in the signal wave form due to melting or distortion of the low-melting-point conductor. The specific temperature to be sensed can be preset by providing preheating of the sensor, as by Joule heating, by passing a current through the low-melting-point conductor.

Abstract: A heat detection apparatus comprising a display face having a protruding member extending therefrom disposed in a fixed frame means and connected to a tension means in a tensioned mode, said protruding member and display face maintained in a first position under tension by a solid retention means disposed with the distal end of said protruding member in communication with said protruding member and frame means with said retention means meltable at an elevated temperature, and wherein melting of said retention means permits relaxation of said tension means resulting in said protruding member and display face moving to a second position under relaxation, and further wherein said display face displays a first indicator of non-elevated temperature in the first position and a second indicator of elevated temperature in the second position.

Abstract: A method of determining the penetration of an isotherm into a mass, including the steps of distributing material in the mass, the material having the ability to fix a record of an isotherm, cycling the temperature of the mass, and checking the material for the location of the isotherm relative to the mass.

Abstract: A coupon is bonded to a component using a bonding agent which is capable of withstanding temperatures only up to a selected temperature above which the bonding agent no longer holds the coupon to the component. The component, during an operation, is intended for exposure to temperatures not above the selected temperature. An exposure of the component to the elevated selected temperature is identified by the fact that the coupon is no longer bonded to the component after termination of the operation. When the component is provided with insulation, the selected temperature is chosen to correspond to a temperature at which the insulation fails to determine the integrity of the insulation after the insulation. The coupon may be bonded to an exterior or interior surface of the component. With an exterior bonded component, visual inspection is sufficient. With an interior bonded component, detection means such as ultrasonic instrumentation is utilized to determine the presence or absence of the bonded coupon.

Abstract: A noninvasive accurate method for measuring the temperature of tissue beneath the surface of a living body 11. Ultrasonic signals (14) are directed into beads 13 of a material that are inserted into the tissue with a syringe. The reflected signals (15) indicate the acoustic impedance or resonance frequency of the beads 13 which in turn indicates the temperature of the tissue. A range of temperatures around the melting temperature of the material can be measured by this method.

Abstract: System and means for irreversibly recording the incidence of a predetermined temperature comprising a cholesteric liquid crystal system and an activator material capable of interacting with the liquid crystal system to induce a unique irreversible change in the optical properties thereof sustantially at the predetermined temperature. The system preferably includes means for separating the liquid crystal system and activator at temperatures below the activation temperature of the activator.

Abstract: A temperature indicating device comprising a series of liquid crystal cells each of which contains a liquid crystal material having a different composition, the composition varying from cell-to-cell, and each of which cells exhibits the grandjean state whereby temperature is indicated by iridescence of the cells, the cells being such that the liquid crystal material in each has a clearing point at a different selected temperature in a series of temperature in a temperature range of interest and that each of the cells is such that its liquid crystal material does not revert immediately to the grandjean state on cooling from the isotropic liquid state wherein the improvement comprises the cells having a construction such that the liquid crystal material of each cell undergoes, on cooling from the isotropic liquid state, the transition isotropic liquid state to focal conic state, without reverting immediately to the grandjean state.

Abstract: A critical temperature indicator is provided utilizing the volume reduction characteristics of organic compounds as they undergo a change from the liquid state to the solid state. A capillary tube sealed at one end contains a first organic compound adjacent the closed end and a second colored organic compound which has a solidification temperature lower than that of the first compound and which is separated from the first compound by a liquid which is immiscible with either the first or the second compounds. The separating liquid also has a solidification temperature lower than that of the first compound. A colorless or white porous plug is located within the separating liquid and frictionally engages the tube to prevent movement of the plug with respect to the tube.

Abstract: A critical temperature indicator is provided utilizing the volume reduction characteristics of organic compounds as they undergo a change from the liquid state to the solid state. The bulb and a portion of the capillary tube of a thermometer-like structure contains a colorless organic compound. Another organic compound saturated with a dye, which compound has a solidification temperature lower than that of the colorless compound and which is miscible with the colorless compound, is located in the capillary tube and separated from the colorless compound by a solid, movable plug or a liquid which is immiscible with either the colorless or the dyed compound. The volume of the colorless compound upon solidification is less than the volume of the bulb so that the separating plug or liquid and at least a portion of the dyed compound are drawn into the bulb upon solidification. The dyed compound then mixes with the colorless compound to provide a visual indication that the colorless compound has solidified.

Abstract: An improved steam sterilization indicator is provided. The indicator includes a fusible material, in tablet form, deposited in an embossment in one end of a thin aluminum backing. A wicking strip is attached to the backing with one end of the strip being in close proximity to the fusible tablet. A clear plastic material covers the tablet and the strip and is adhered to the backing. The melting point of the fusible tablet is depressed in the presence of saturated steam. Upon melt, the material in the tablet is absorbed by the wicking strip, producing a color front to provide an indication of the integration of time and temperature in the presence of steam. Various amounts of a binder are used in the tablet to provide a device which may be adjusted to reflect the thermal death curves of various types of microorganisms. The cover and the wick are bonded to the backing by an acrylic adhesive which also affects the rate of the indicator.

Abstract: Cholesteric liquid crystals of the so-called reentrant mesogenic type obtained by mixing a substance such as a cholesterol ester having molecules of the "chiral" type with a liquid crystal of the so-called reentrant nematic type such as a substance corresponding to the general formula: ##STR1## where R is an alkyl or alkoxy or alkylcarbonate group with:R'=H or CH.sub.3and X is an organic radical such that CH=N, CH=CH, C.tbd.C or COO.The use of a liquid crystal in accordance with the invention serves to obtain a temperature-detecting device in which, in contrast to conventional cholesteric devices, the reflected light changes from blue to red when the temperature rises.

Abstract: A temperature profile detector shown as a tubular enclosure surrounding an elongated electrical conductor having a plurality of meltable conductive segments surrounding it. Duplicative meltable segments are spaced apart from one another along the length of the enclosure. Electrical insulators surround these elements to confine molten material from the segments in bridging contact between the conductor and a second electrical conductor, which might be the confining tube. The location and rate of growth of the resulting short circuits between the two conductors can be monitored by measuring changes in electrical resistance between terminals at both ends of the two conductors. Additional conductors and separate sets of meltable segments operational at differing temperatures can be monitored simultaneously for measuring different temperature profiles.

Abstract: Minute durable plate-like thermal indicators are employed for precision measuring static and dynamic temperatures of well drilling fluids. The indicators are small enough and sufficiently durable to be circulated in the well with drilling fluids during the drilling operation. The indicators include a heat resistant indicating layer, a coacting meltable solid component and a retainer body which serves to unitize each indicator and which may carry permanent indicator identifying indicia. The indicators are recovered from the drilling fluid at ground level by known techniques.

Abstract: Disclosure is made of novel temperature sensing devices such as temperature indicating and recording devices. The devices of the invention differ from prior art devices in that they employ new and improved temperature indicating compositions. The temperature indicating compositions of the invention comprise an optically active, non-cholesteric inert compound in admixture with nematic type liquid crystal compounds. The optically active, inert compounds lend a visible point of reference to the compositions when the liquid crystals pass through their liquid transition points. The proportion of optically active, inert compounds added to the nematic liquid crystals is that proportion which will impart chirality or twist to the compositions of the invention and is dependent upon the twisting power of the optically active ingredient. The compositions of the invention are unique in that they possess very sharp liquid transition points, i.e.; clearing points over a very narrow temperature range.

Abstract: Novel and stable compositions of matter are disclosed which change color sharply upon a transition from a liquid state to a solid state or from a solid state to a liquid state, which change of state is at substantially a predetermined temperature corresponding to a temperature to be measured.The constituents of the novel compositions of matter comprise:1. a solvent (I) consisting of a single substance or a mixture of substances and adapted to change from a solid state at substantially a predetermined temperature to a liquid state and2. an indicator system (II) consisting of one or more substances different from (I), characterized in that(a) (II) is soluble in (I) when the latter is in the liquid phase, and(b) (II) changes color visible to the naked eye when (I) passes from the solid to the liquid phase or from the liquid to the solid phase.Thermometers containing said stable compositions of matter are also disclosed.

Abstract: A pop-up type temperature indicator is adapted to be inserted in poultry or other meat to indicate that a preselected temperature has been reached. The indicator includes a housing having a bore, a movable temperature-indicating element in the bore, and a temperature-sensing member having an elongated needle projection from a lower portion of the housing and a head adjacent a lower portion of the temperature-indicating element. The temperature-sensing member is made of metal, and a thin film of a solidified fusible alloy normally secures the head of the temperature-sensing member to the temperature-indicating element to retain the element in a fixed position in the bore. A coil spring biased against the temperature-indicating element applies force to the element for triggering movement of the element in the bore upon melting of the fusible alloy at a preselected temperature sensed by the temperature-sensing member.

Abstract: A device for monitoring thermal energy input and displaying the relationship of the thermal energy input to a selected time/temperature relationship. The device employs an indicating material which, when melted, expands and flows into a narrow channel to provide an irreversible, visible indication of the thermal energy to which the device has been exposed.

Abstract: A novel temperature indicating device is disclosed comprising: (a) a flat or gradually curved heat-conducting carrier having one or more cavities, each substantially filled with a novel composition of matter (NTICM), as described herein; or in the alternative, with (1) a `classical` composition of matter which changes from opaque to transparent upon a corresponding change from solid to liquid on top of an (2) indicator means located at the bottom of the cavity; said composition of matter, whether novel or not, being substantially without impurities and containing a substantially spherical void space between the bottom of the cavity; and (b) a transparent cover sheet means in sealing engagement with the heat conducting carrier means overlying and above the cavity, which spherical void space acts to magnify the color change if the novel compositions of matter are present or the presence of an indicator means upon melting of the `classical` compositions of matter in the cavity.

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: An improved steam sterilization indicator is provided. The indicator includes a fusible material in tablet form, deposited in an embossment in one end of a thin aluminum backing. A wicking strip is attached to the backing with one end of the strip being in close proximity to the fusible tablet. A clear plastic material covers the tablet and the strip and is adhered to the backing. The melting point of the fusible tablet is depressed in the presence of saturated steam. Upon melt, the material in the tablet is absorbed by the wicking strip, producing a color front to provide an indication of the integration of time and temperature in the presence of steam. Various amounts of a binder are used in the tablet to provide a device which may be adjusted to reflect the thermal death curves of various types of microorganisms. The cover and the wick are bonded to the backing by an acyclic adhesive which also affects the rate of the indicator.