Sugar wash calculator

How to use it

1. Choose your sugar. White sugar is the standard. Dextrose, honey and molasses carry water or unfermentable solids, and the calculator allows for both.
2. Choose the direction. From the sugar if you know how much you'll use; For a target strength to find out how much to buy.
3. Enter the water. The water you will dissolve the sugar in. The calculator adds the room the sugar takes up, and the water that honey and molasses carry, and shows the volume of the finished wash.
4. Mix and measure. Dissolve the sugar in part of the water (warm water helps), top up to the mark, and check the starting gravity with a hydrometer before you add the yeast. Keep that reading: the hydrometer calculator turns it into a strength once fermentation has finished.

How it works

Gravity. The calculator works out how much sugar is dissolved in each litre, and from that the strength in °Brix (or °Plato, practically the same) and the specific gravity, using the standard relation for sugar solutions.

Alcohol. In theory, each kilogram of white sugar can become 538 g of alcohol, with the rest leaving as carbon dioxide. In practice the yeast keeps some for its own growth and turns a little into other compounds, so the calculator assumes about 86% of the theoretical yield - roughly 16–17 g of sugar per litre for each 1% of alcohol. It shows the theoretical maximum too.

Other sugars. Dextrose (corn sugar) is sold as a hydrate and is about nine-tenths sugar; honey is around four-fifths sugar and the rest water; blackstrap molasses is only about half fermentable sugar, and varies a great deal.

Worked examples

4.5 kg of white sugar in 22 L of water makes 24.8 L of wash with a starting gravity of 1.070 (17.0 °Brix). It should ferment to about 10.7% ABV, against a theoretical 12.4%.

For a 10% wash from 22 L of water, you need 4.19 kg of white sugar, or 5.8 kg of honey.

In US units, 8 lb of sugar in 5 gallons of water starts at 1.066 and should reach about 10.1% ABV.

Questions

What starting gravity should a sugar wash have?

Most sugar washes start between about 1.060 and 1.090, for 8–12% alcohol. Stronger washes stress the yeast, ferment more slowly and can stall; bread and distillers' yeasts manage up to about 12–14%.

How much sugar do I need for a 10% wash?

About 190 g of white sugar for each litre of water (4.19 kg for 22 L), assuming it ferments dry.

Why is my wash weaker than the calculator says?

Usually because it hasn't finished: it is done when the gravity stays the same for two or three days. A wash that stops early is often too cold, short of nutrients or too strong for its yeast.

Does inverting sugar give more alcohol?

No. Yeast inverts sugar itself, so the same sugar gives the same alcohol either way. The inverted sugar guide explains what inverting does and doesn't do.

Does a sugar wash need nutrients?

Yes. Sugar is almost pure sucrose, with none of the nitrogen, vitamins and minerals yeast needs. The recipes show what each one uses, from tomato paste and lemon juice to bran.