One of the qualities of good porter, is, that it should bear _a fine frothy head_, as it is technically termed: because professed judges of this beverage, would not pronounce the liquor excellent, although it possessed all other good qualities of porter, without this requisite.
To impart to porter this property of frothing when poured from one vessel into another, or to produce what is also termed a _cauliflower head_, the mixture called _beer-heading_, composed of common green vitriol (sulphate of iron,) alum, and salt, is added. This addition to the beer is generally made by the publicans.[61] It is unnecessary to genuine beer, which of itself possesses the property of bearing a strong white froth, without these additions; and it is only in consequence of table beer being mixed with strong beer, that the frothing property of the porter is lost. From experiments I have tried on this subject, I have reason to believe that the sulphate of iron, added for that purpose, does not possess the power ascribed to it. But the publicans frequently, when they fine a butt of beer, by means of isinglass, adulterate the porter at the same time with table beer, together with a quantity of molasses and a small portion of extract of gentian root, to keep up the peculiar flavour of the porter; and it is to the molasses chiefly, which gives a spissitude to the beer, that the frothing property must be ascribed; for, without it, the sulphate of iron does not produce the property of frothing in diluted beer.
Capsicum and grains of paradise, two highly acrid substances, are employed to give a pungent taste to weak insipid beer. Of late, a concentrated tincture of these articles, to be used for a similar purpose, and possessing a powerful effect, has appeared in the price-currents of brewers' druggists. Ginger root, coriander seed, and orange peels, are employed as flavouring substances chiefly by the ale brewers.
From these statements, and the seizures that have been made of illegal ingredients at various breweries, it is obvious that the adulterations of beer are not imaginary. It will be noticed, however, that some of the sophistications are comparatively harmless, whilst others are effected by substances deleterious to health.