A RUBBER IS DEFINED BY THREE FUNDAMENTAL FACTORS:

For the gumming of lids, we start from a quantity of gum necessary for each format of lid, calculated in turn, by a volume of dry gum per linear cm to be gummed, which can vary depending on the width of the channel, the size of the closure to be made or depending on the type of container (welded, deep-drawn, round, rectangular, etc.). It can be considered as normal between 2 and 3 mm3.

Taking this into account, for a given cap, a volume of dry rubber to be applied, VS, is defined, so the weight of dry rubber defined for a cap, PS, will be a function of this volume of dry rubber, multiplied by the density of the dry rubber:

Similarly, the weight of wet gum PH, needed to gum a cap, will be a function of the dry weight, PS, and its dry extract, ST:

Therefore, the volume of wet rubber VH, will be a function of the weight of wet rubber, PH divided by the density of wet rubber, DH:

Making the corresponding substitutions, we come to the conclusion that the volume of wet rubber can be obtained according to the following formula: