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The converter below can be used to convert between % Extract values that might appear on a malt specification (spec) sheet. These conversions can be necessary to determine brewhouse efficiency or to determining the grain bill required for a brew. For an explanation of how the calculator works and what the units mean read the 'Explanation of the Calculator' section below.
To use the calculator enter the % extract to be converted into the yellow box
below and select its units using the drop down box. Malt moisture and c.g. f.g.
diff. are also needed for some conversions. Once you have entered all of your
input data hit 'Calculate' to convert.
Explanation of the Calculator.
The units used in this calculator are:
f.g. d.b. (%) = % extract yield on a fine grind dry basis.
c.g. d.b. (%) = % extract yield on a course grind dry basis.
c.g. as is (%) = % extract yield on a moisture 'as is' basis.
c.g. f.g. diff (%) = difference in % yield between f.g. d.b. and c.g. d.b.
The equations used in this conversion calculator are very simple:
% extract f.g. d.b. = % extract c.g. d.b. + % c.g. f.g. diff.
% extract c.g. as is. = % extract c.g. d.b. x (1- % moisture)
The % Extract (or % Extract Yield) value listed on malt spec sheets and in brewing texts is the percentage of malt weight that is converted to dissolved wort extract in a laboratory mash (Holle and Klimovitz 2003).
The laboratory will do a mash on the malt under very specific conditions (called a congress mash) with the malt milled at either 0.2mm (fine grind, f.g.) or 0.7mm (course grind, c.g.) or both. The extract values obtained are then converted to a dry basis (d.b.) as the actual moisture of the malt may vary between shipments (Holle and Klimovitz 2003).
Generally the c.g. d.b. is most useful in the brewhouse as it can be used to determine brewhouse efficiency or for determining the grain bill required for a brew. These calculations may require the % extract value to be converted back to a moisture 'as is' basis so we have included a course grind 'as is' (c.g. as is) unit in the calculator (although many calculators and equations will simply ask for a c.g. d.b. value and a % moisture value and do the sums for you). The c.g. as is unit can sometimes be displayed on malt spec sheets but it is uncommon. If the unit for Extract % is not displayed on a malt spec sheet then it is probably on a c.g. d.b., but it is worth contacting the malt house or supplier to confirm this as it is not always the case.
To avoid confusion for those of you that are not familiar with the term brewhouse efficiency (well in an attempt to avoid confusion) it has to be stated that a congress mash % extract yield will be higher than the % extract yield that can be obtained in a brewery (unless you have a multi-million dollar mash filter). Brewhouse efficiency is simply the % of extract yield obtained in the brewery mash compared to the extract yield obtained in a c.g. congress mash.
Brewhouse Efficieny % = Brewhouse Mash Yield / c.g. as is Congress Mash Yield.
Some of you may be asking 'why do the malt spec sheets use a f.g. basis if it can't be used in brewhouse calculations?'. Well, one of the main reasons is that the difference between the c.g. and f.g. % extract gives an indication to the degree of modification of the malt. If the malt is undermodified then the c.g. grist will not break up as much as it is milled and will produce less extract than a well modified malt. The f.g. grist will also produce slightly less extract in an undermodified malt but not to the same degree as it is so finely milled. Therefore the difference between the f.g. and c.g. % extract values will be larger in undermodified malts.
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