Today in 1939, US Patent 2181931 A was issued, an invention of Lyndon D. Wood, assigned to National Hops Lab, Inc., for his “Process for Extracting the Essential Principles of Hops.” There’s no Abstract, although in the description it includes this summary:

My process is essentially as follows:

My first procedure is to suitably prepare the hops by pulverizing them to’ a degree of fineness sufficient to crush all of the seeds which they contain and finely enough so that they will pass a 20 mesh screen or sieve. This may be done in any one of several types of mills which can be adapted for the work such as a ball mill, plate mill, roller mill, or a cutting mill, or a combination of cutting and hammer mill. The mill should be enclosed so that no air current are present in which the aroma of the hops can be dispersed. From the mill the prepared or pulverized hops should be conveyed to a closed tank or receptacle where the solvent is applied.

When old hops are used in which the lupulin has hardened and particularly those in which a rancid odor has occurred from the oxidation of hop oil, I employ activated carbon, which may be made from the vegetable, fibrous material of the hops residue after extraction has been made.

This activated carbon may be used in two ways. (a) By mixing it in finely powdered form with the pulverized hops while they are in a dry state.

When this method is employed ounce of activated carbon will be used to each pound of pulverized hops. The prepared hops should be stirred and shaken until the activated carbon has been thoroughly mixed with them, then be permitted to stand in a closed container for a period of time not less than two hours. The activated carbon experiments have shown restores the odor of fresh hops.