FermCalc - Miscellaneous Additive Calculations

Introduction

The Miscellaneous Additive Calculations panel has three functions:

1. Converting a dry weight (mass) to an approximate dry volume for a number of common winemaking additives.
2. Calculating the mass of an additive required to make a stock solution with a specified volume and concentration.
3. Calculating the mass of an additive or the volume of a stock solution to add to a wine to yield a target concentration in the wine.

Making a Calculation

To make a calculation, follow these steps:

1. Select Calculation > Miscellaneous Additives from the menu, or select the Miscellaneous tab at the top of the main window.
2. Select the type of calculation by selecting either the Dry Measures tab, the Stock Solutions tab, or the Miscellaneous Additions tab.
3. Select the appropriate units for the input fields using the drop-down menus in the right-hand column.
4. If Dry Measures was selected:
   1. Select the Additive from the dropdown list, and then enter the Dry Weight (Mass) of Additive in the appropriate field.
   2. The Approximate Dry Volume of Additive will appear in the output field.
5. If Stock Solutions was selected:
   1. Enter the Target Concentration and the Solution Volume of the solution that you wish to make in the appropriate fields. Please note that the Solution Volume represents the total volume of both the additive and water, not the initial volume of the water.
   2. The Mass of Additive Required will appear in the output field. 
6. If Miscellaneous Additions was selected:
   1. First select the Additive Type (either solid or liquid) and if it's liquid enter the Concentration of the solution.
   2. Next enter the Target Concentration, the Initial Concentration, and the Wine Volume.
   3. The Mass of Additive Required or Volume of Solution Required will then appear in the output field.

Calculation details are provided below.

1. Dry Measures
2. Stock Solutions
3. Miscellaneous Additions

Calculation Details - Dry Measures

This calculation converts a dry weight (mass) to an approximate dry volume for a number of common winemaking additives. This is designed for home winemakers who don't have accurate scales and instead add ingredients by dry volume (teaspoons, mL, etc.).

All of the conversion factors are based on Jack Keller's "Measuring Additives in Winemaking", except for the sugar and sodium metabisulfite conversions which are based on my own measurements. Please be aware that these conversions are approximate.

Calculation Details - Stock Solution Formulation

This calculation determines the amount of a substance required to yield a stock solution with a given volume and concentration. Concentrations are specified in terms of mass per unit volume. So, the required mass is simply the volume multiplied by the concentration, or:

ma = vscs

(1)

where

m_a = mass of additive, kg
v_s = solution volume, liters
c_s = concentration of substance in solution, kg/L

Calculation Details - Miscellaneous Additions

This calculation determines the amount of a substance to add to a wine to yield a desired concentration in the wine, given the initial concentration of the substance and the wine volume. The substance can either be in the form of a solid (powder or crystals) or a liquid (stock solution).

If it is being added as a liquid, the concentration of the solution must be specified. It is assumed that the volume of the additive is negligible compared to the volume of the wine, and that the increase in volume due to the addition can be ignored. If the volume of the solution addition is greater than 10% of the volume of the wine, FermCalc will issue a warning message. In this case, consider doing a blending calculation to account for the impact of the volume increase on the final concentration.

The total mass of a substance in solution is simply the initial mass of the substance plus the mass that is added, or:

mt = mi + ma

(2)

where

m_t = total mass of substance, kg
m_i = initial mass of substance, kg
m_a = mass of substance added, kg

Since mass is volume multiplied by concentration we can write:

vwct = vwci + ma

(3)

where

v_w = wine volume, liters
c_t = total (target) concentration, kg/L
c_i = initial concentration, kg/L

Rearranging and solving for m_a we get:

ma = vw(ct - ci)

(4)

If the substance is being added as a stock solution, we need to calculate the volume of the solution to add. To do this we simply need to substitute equation (1) for m_a in equation (4) and rearrange to get:

vs = vw(ct - ci)/cs

(5)

© 2007-2010 Steve Gross
Last updated 06 May 2010.