other than in the operating examples , or where otherwise indicated , all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as being modified in all instances by the term &# 34 ; about &# 34 ;. it has been surprisingly discovered that certain additives have a tendency to enhance the degree to which molecules in a substrate are excited , thus causing more heat to be dissipated when the substrate is exposed to microwave energy , thus providing energy cost savings . as was noted above , water is a molecule that is readily excited by microwaves and is often times the primary microwave absorber in microwavable substrates . thus , it has also been discovered that by combining water with an additive of the present invention , heating rates can be controlled over a continuum between water and the additive . the additives which may be employed in accordance with the present invention , as heat controlling additives , are aliphatic polyols . examples of aliphatic polyols which may be used include , but are not limited to , ethylene glycol , propylene glycol , 1 , 3 propane diol , 1 , 4 - butane diol , glycerin , 1 , 3 butylene glycol , neopentyl glycol , penta - erythritol , di - penta - erythritol , and mixtures thereof . a particularly preferred aliphatic polyol is glycerin . as to the microwavable substrates which may be employed , any substrates capable of being microwaved are contemplated by the present invention . examples of microwavable substrates which may be employed include , but are not limited to , microwavable food items , heat packs , compresses , and the like . the microwave energy used to excite the molecules in the microwavable substrate will have a frequency ranging from about 500 to about 100 , 000 mhz , and preferably from about 900 to about 2500 mhz . according to one aspect of the invention , there is provided a process for controlling the rate at which a microwavable substrate is heated by combining it with an effective amount of the above - disclosed polyol . the precise effective amount will depend on the particular microwavable substrate employed and the precise degree ( continuum ) of heating desired . in a particularly preferred embodiment of the present invention , the additive further includes water , in admixture with a polyol . once again , the ratio by weight of water : polyol will be dependent on the particular microwavable substrate employed and the precise degree ( continuum ) of heating desired . in a particularly preferred embodiment , the ratio by weight of water to polyol will range from about 1 : 10 to about 10 : 1 . the present invention will be better understood from the examples which follow , all of which are meant to be illustrative only and are not meant to unduly limit the scope of the invention in any way . unless otherwise indicated , percentages are on a weight - by - weight basis . various polyols , water , and mixtures thereof , in sample sizes of 175 ml , and at starting temperatures of 24 ° c . were heated in a conventional microwave oven , over varying time intervals and at varying microwave power levels , to determine their heating rates . the results hereof are found in tables 1 and 2 below , as well as fig1 - 3 . table 1______________________________________ di water / glycerin water / glycerin water glycerin ( 50 / 50 ) ( 20 / 80 ) ______________________________________time at 1 kw 30 sec 44 ° c . 55 ° c . 47 ° c . 56 ° c . 60 sec 64 ° c . 85 ° c . 72 ° c . 84 ° c . 90 sec 84 ° c . 113 ° c . 98 ° c . 110 ° c . time at . 5 kw 60 sec 49 ° c . 63 ° c . 56 ° c . 62 ° c . 90 sec 64 ° c . 81 ° c . 72 ° c . 77 ° c . 120 sec 74 ° c . 92 ° c . 79 ° c . 87 ° c . 180 sec 94 ° c . 123 ° c . 103 ° c . 114 ° c . ______________________________________ table 2______________________________________ propyl - 1 , 4 - time at dimer ene ethylene butane gly - veg . di 1 kw diol glycol glycol diol cerin oil lard water______________________________________30 sec 45 57 56 64 55 48 56 43 60 sec 72 91 88 102 85 66 72 67 90 sec 101 121 114 130 113 92 91 91______________________________________
a process for controlling microwave heating rates involving : providing a microwavable substrate ; combining the microwavable substrate with an additive consisting essentially of an aliphatic polyol to form a modified microwavable substrate ; and subjecting the modified microwavable substrate to microwave energy .