This invention relates generally to articles of apparel, and more particularly to methods of repeatedly storing heat in such articles of apparel. 
For the purposes of this invention, the term "article of apparel" includes, but should not be considered as being limited to, clothing and other accessories which are worn or carried by a person.  That is, the term "article of apparel" as is used herein denotes handwear, including gloves, mittens, muffs, hybrid glove-mitten designs, and other such means to be worn inside or as an accessory to handwear (e.g., by slipping such means inside of the handwear, by strapping such means on the handwear, or by attaching such means to the handwear such as by Velcro. RTM.). 
"Article of apparel" also refers to headwear (including earmuffs, headbands, hats, bandannas, yarmulkes, face masks, varied combinations of such types of headwear, and other such means to be worn inside or as an accessory to headwear); footwear (including slippers, shoes, boots, socks, insoles, arch supports, footwear inserts or other accessories to footwear); neckwear (including scarves, neckties, dickies, collars, or accessories to neckwear); various bodywear of a size that is capable of being fitted into a conventional microwave oven, which usually ranges in capacity of from 0.2 cubic feet to 5.0 cubic feet, including vests, jackets, undergarments, pocket warmers, and other such means to be worn inside or as an accessory to bodywear (e.g., by slipping such means inside of the bodywear, by strapping such means on the bodywear, or by attaching such means to the bodywear such as by Velcro. RTM.). 
It should also be noted that the term "article of apparel" herein encompasses toys (including dolls, carryable or huggable objects, renditions of food items, real or fictitious creatures, wearable toys and puppets); therapeutic appliances; and other objects which are preformed or compliant to body parts to which they would be applied (including pouches, bottles, bags, hot packs, compresses, wraps, masks, and other such means that are slipped inside of the therapeutic appliance, strapped on, buttoned on, or otherwise attached to the therapeutic appliance such as by Velcro. RTM.). 
Not only does an "article of apparel", as that term is used herein, include objects that are worn or carried by a person, but also other objects as exemplified above which are adapted to be worn or carried by, or applied to animals or other such living things. 
2.  Statement of the Prior Art
Since his beginnings man has been searching for methods and apparatus to keep warm.  Warmth, provided by any suitable means, not only enables man to extend his range of activities to colder climates but also promotes a feeling of security.  For example, a child can often be seen clutching a blanket or doll in order to be actually warmed by the blanket or doll and reassured by its presence. 
The prior art is replete with means and methods of conserving the body's own warmth.  Other means and methods have been developed to provide extracorporeal warming of various parts of the human anatomy, especially gloves and mittens for warming the hands of the wearer.  Such known means and methods can be conveniently categorized under two typical approaches--electrical heating and chemical heating.  For example, Maxwell et al.  in U.S. Pat.  No.  3,292,628 discloses an electric therapeutic glove comprised of an outside cover and inside liner between which is situated heating elements held in place by retaining screens, the heating elements being electrically energized as controlled by a thermostat. 
In U.S. Pat.  No.  3,569,666 issued to Murphy et al.,  a self-contained low voltage battery-operated glove is disclosed.  The glove has a hand receiving portion, comprised of an outer covering and a complementary inner liner, and a wrist engaging portion in which a low voltage resistance heater is connected adjacent to the fingertip end portion of the inner palm side of the glove.  The heater comprises a bare strip of electrical resistance material, sandwiched between a heat diffusing material, which is connected to the wrist portion of the glove on the back side thereof. 
Monk, in U.S. Pat.  No.  4,543,671, discloses a heated mitten which includes a main body for covering the hand and fingers of a wearer, and a thumb sheath together with an elasticated wrist band.  The main body comprises a palm or front portion and a back or rear portion between which is formed a sealable compartment or pouch at the top of the mitten.  The pouch includes an opening through which an electrical heating element is introduced, and is adapted to be moved to the front or back of the hand as necessary for warmth. 
One obvious drawback to each of the above described electrically heated gloves or mittens is the necessity for a source of electrical power.  Batteries often fail, and their subsequent replacement is often delayed because of lack of stores selling such batteries or because of a scarcity of batteries of a particularly required size.  Another drawback is the repeated expense of the batteries and the lack of money at the time of need for such batteries.  Furthermore, batteries perform suboptimally in cold weather which can impede the chemical reactions which produce the electrical outflow.  Moreover, wear and tear on the gloves or mittens which incorporate such electrical heating elements increases the likelihood of shock or failure should the heating element become bare.  It would, therefore, be desirable to provide an article of apparel, such as a glove, a mitten, or a cap, and method of heating same which does not require integral electrical heating means. 
The other prior art approach--chemical heating--is also subject to many variations.  For example, in U.S. Pat.  No.  2,792,827 issued to Gravin et al.,  a heated glove is disclosed.  The glove has a heating chamber formed as an auxiliary glove compartment which includes a waterproof and insulated main body with thumb and fingers superposing the main body, thumb and fingers of the hand of the glove.  A heating tablet, powder or capsule is introduced within the heating chamber through its opened outer end together with a small quantity of water or other liquid, in order to develop heat through exothermic reaction.  While any known heat generating chemicals, according to Gravin et al.,  may be used for the tablet, powder or capsule, the glove also utilizes a moisture absorbent layer on the interior of the heating chamber to prolong the chemical reaction between the moisture and such chemical composition. 
Spector et al.,  in U.S. Pat.  No.  4,535,482, discloses a heated glove having an inner layer of insulated material forming a sealable top pocket to hold a conventional fuel burning type hand warmer.  Five ducts, each of which extend from the top pocket over a respective finger, provide warm air to the wearer's hand through a plurality of holes.  The pocket is further provided with a top heat reflecting layer extending through the ducts, a zipper to close the pocket, and mesh screen placed below the zipper to allow ambient air to enter the pocket to supply oxygen to the hand warmer. 
As is also disclosed in U.S. Pat.  No.  4,587,672, issued to Madnick et al.,  a cold-weather hand covering can include a selectively shaped chemical heating element receiving chamber.  Ten different embodiments of the cold-weather hand covering are shown, each including means for removably retaining the shaped element in its correspondingly shaped chamber. 
While each of the above described chemical heating approaches eliminates the undesirable characteristic of having to be dependent upon a source of electricity as in the previously described electrical heating apparatus, such chemical heating apparatus nevertheless involves the usage of exhaustible and potentially undesirable components.  It would, therefore, be more desirable to provide an article of apparel and method of heating same which permits the article to be repeatedly reheated without the presence of potentially undesirable and expendable chemical components. 
The desirability to provide articles of apparel and method of heating same does not merely extend to article of apparel comprising pieces of clothing (e.g., glove, mittens or caps).  Other articles, such as dolls, have been heated in the past in order to simulate the body temperature of an infant such that the carrier of the doll (most often a child) enjoys a greater sense of security and reality.  For example, U.S. Pat.  No.  4,060,932 issued to Leto et al.  discloses a doll with an internal warming mechanism comprised of an internal vessel containing an exothermic salt and means to introduce water into the vessel to activate the salt and thereby release heat. 
Pittala, in U.S. Pat.  No.  4,209,939, also discloses a doll using circulating fluid to simulate body temperature.  A skin structure in the doll, comprised of a spaced layer and stud passageway, permits fluid warmed by an electrically heated reservoir to be circulated throughout the doll.  For the same reasons noted herein above with respect to the electrically and chemically heated gloves and mittens, however, a doll having some other means and method for warming the doll would be much more desirable.