“Gyle” is the whole brew derived from one mash; “Parti” is “parts of”. Therefore, from one charge of malt (grist) in the mash tun, multiple worts are derived. The grist is soaked in hot water (liquor), stirred – referred to historically as mashing, and left to stand. This first mash is drained, and the resulting liquid is termed the first wort. Soaking, stirring and draining are repeated to obtain up to four or five worts; five is the absolute limit, the last is sometimes used in the next day’s brew and sometimes termed the “return” wort. The first mash and its temperature determine the sugar profile of the gyle; subsequent mashes merely wash out the fermentable material remaining from the previous mashes. It hardly needs to be stated that the first wort will be the sweetest and subsequent worts progressively diluted, the last containing little fermentable material and making a weak beer/ale termed “small beer”. The system is flexible in that separate beers of diminishing strength may be made; the worts may be combined to make beers of defined strength, or the worts may be combined into one beer, called “entire”.
Sparge Explained
The grist is mixed with hot water, and left to stand. When the tap is opened and draining begins, water (liquor) is continuously sprinkled over the malt to wash out remaining fermentable material. The rinsing will normally continue until the specific gravity of the runnings reaches 5 (1.005). At this point all the valuable sugars have been extracted and any further sparging will extract harsh bitter tannins.
N.B. Historically, the act of stirring was called mashing. Today mashing is the action of enzymes to convert starch to sugars which occurs after the initial stirring or mixing.
Parti-Gyle to Sparge
By the 18th century the process of “leaking on” was beginning to be documented. This was gradual pouring of liquor on to the mash while wort drained from the tap of the mash tun. This leisurely action could take hours but conserved liquor and obtained maximum extract from the malt.
Around 1743 Dr. Robert Barker invented the “Barker’s Mill”. This precursor to the water turbine channeled water down a central pipe to tangential nozzles, creating torque and turning the assembly. The design was not strong enough to drive a mill but could sprinkle water through revolving arms. Scottish brewers turned the invention upside down to sprinkle liquor evenly over the surface of the mash. Instead of the old multiple mash system, extract could be washed from the malt in one continuous operation. English brewers started using the Scottish system in the early 19th century.
From Old French espargier or Latin spargere, to sprinkle – OED
In the words of Tizard: “The saving of many mashes or comminglings is one act of expedition [partigyle]; and that of a protracted sparging (from spargo, to sprinkle) …is another;..” (William Little Tizard, The Theory and Practice of Brewing Illustrated 1846, page 189).
If you’re not continuously sprinkling you are not sparging. Batch sparging is a misnomer.
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