🍺 Top-down Brew: Mash Efficiency - Advanced

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Results

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Notes

This mash efficiency calculator is modeled after Palmer's (2001, p. 148 - 152) description and "Short Stout" example. The approach is based upon specific gravity points (GP) for each grain (e.g., 1.037 is 37 points) in each gallon or liter. The actual or obtained gravity points are divided by the theoretically possible points to determine the efficiency percentage. Gravity contributions from malt extract and sugar are subtracted from the grain points to focus the results entirely upon mash efficiency.

For example, consider a wort of 1 gallon made from 1 pound of two-row malt. The formula for gallons and pounds multiplies the weight by theoretical maximum possible yield. The weight of 1 lb * 1.037 (expressed as points) = 37 points. This is adjusted for volume: 37 / 1 gallon = 37 or 1.037 as SG. This means that 1.037 would be the highest possible gravity from 1 lb of malt in one gallon of wort: 100% efficiency. If the actual wort is 1.032, then 32 (actual points) / 37 (theoretical points) * 100 = 86.5% efficiency

US Units:

GP for each grain: (pounds * maximum yield expressed as SG points) / gallons
Mash efficiency % = ((actual gravity points - sugar gravity points) / malt theoretical gravity points) * 100

The metric approach is similar. It is based on a maximum hot water extract of 384 L°/kg modified by the malt SG point value over 46 (the gravity point value of pure sucrose). This is multiplied by weight in kg and adjusted for volume.

GP for each grain: (kilograms * 384 * (maximum yield as SG points / 46)) / liters

The calculations were validated by comparison to Palmer's "Short Stout" example. The results are nearly identical, with some small deviations due to differences in anticipated specialty malt yield.

Reference

Palmer, J. (2001). How to Brew. Second edition. Defenestrative Publishing Co.

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