Specific gravity readings during sparge

Taken from Homebrew Digest 2379
Date: Wed, 19 Mar 1997 10:48:56 -0800 (PST)
From: Domenick Venezia
Subject: Runoff Gravity Change Equation

The recent discussion about deriving functions to describe SG changes during sparging has lacked any data. As such, discussion to date has, by definition, been baseless. Below are the results of SG measurements during the sparge from 10 5 gallon batches.

All SG readings are corrected to 59F. The batches have been numbered 1-10. All mashes took place in a 10 gallon Gott cooler with pizza pan false botton (about 1 pint of foundation space). All sparges had at least 1 gallon recirculated before any readings were taken. Most batches had 1.5-2.0 gallons of boiling sparge water dumped into the 10 gallon Gott as mashout raising the temp to >= 168F.

The readings represent the SG observed after X gallons had been collected. TotVol is the total volume collected during the sparge, and TotSG is the SG of the total volume collected.

Blank entries have no data.

Details for each batch are available.
Batch Number
gal 1 2 3 4 5 6 7 8 9 10
0.0 1.063 1.054 1.062 1.065 1.073 1.066 1.068 1.088 1.062 1.063
1.0 1.062 1.071
2.0 1.053 1.055 1.056 1.051 1.061 1.059 1.073 1.057 1.057
3.0 1.035 1.061
4.0 1.025 1.026 1.036 1.029 1.041 1.048 1.051 1.038
5.0 1.009 1.032
6.0 1.012 1.010 1.018 1.022 1.036 1.021
7.0 1.014 1.008 1.017
8.0 1.005 1.012 1.015 1.018
9.0 1.012
TotVol 7.75 8.00 8.00 8.00 7.00 8.00 7.80 8.50 9.00 8.00
TotSG 1.034 1.030 1.032 1.031 1.033 1.041 1.044 1.042 1.041 1.038

Domenick Venezia
Computer Resources
ZymoGenetics, Inc.
Seattle, WA
venezia@zgi.com
Spencer Thomas created the graph from the data by the following procedure:
  1. Divide the data in each column by the initial SG (0 gallons) to get numbers in the 0.0 - 1.0 range.
  2. Fill in the holes by linearly interpolating.

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Spencer W. Thomas (spencer@umich.edu)

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