Q. I want to add dark sugar flavors to an ale and am thinking about priming with muscovado sugar instead of corn sugar. This got me wondering, when using other types of sugar like muscovado, brown sugar, or maple syrup, is the addition amount always similar to corn sugar (I usually use ¾ cup of corn sugar for a 5-gallon/19-L batch). 
James Eaton
Via email

Mr. Wizard Says…

A. Using flavorful sugars and syrups for bottle conditioning is definitely a way to add flavor to beer. One helpful way to assess the contribution of these ingredients is to add a dose to chlorine-free water — distilled or reverse osmosis works well — at the same rate you would use for conditioning. In this sort of trial, mentally zero out the sweetness and focus on other flavors, aromas, and color, because those are the components that remain after the sugar is converted to carbon dioxide and alcohol.

The dosage rate of priming sugars, whether solid or liquid, is best measured by weight. And for accurate priming, beer volume is essential. Although it is possible to prime individual bottles using bottle volume in the calculation, this method is tedious and best reserved for small bottling runs unless you simply love the process. Whether you use a bottling bucket, keg, fermenter, or carboy for batch dosing, you must know the beer volume. While the exact carbon dioxide content of beer post-fermentation is also required, an estimate is sufficient for establishing a dosing range.

The first step is determining how much carbon dioxide you need to add. Most beers contain about 4.4–6.0 grams of carbon dioxide per liter of beer, which corresponds to roughly 2.2–3.0 volumes, but priming calculations are simplest in g/L, so we’ll stick with that. Most beers fermented atmospherically, i.e., without a spunding valve, contain 2–3 g/L of CO₂. This means we need to add between 1.4–4.0 g/L. For the examples that follow, I’ll use 3 g/L.

The second step is calculating the total carbon dioxide requirement supplied by fermentation of the priming sugar. Knowing the beer volume is essential for anything more precise than an educated guess. Common methods include calibrated sight strips on translucent or clear vessels, dipsticks, or determining the net weight of a stainless steel tank (with the beer’s specific gravity known). For this discussion, let’s assume 15 liters of beer are ready to bottle. The carbon dioxide required from priming sugar is 15 liters × 3.0 g/L = 45 grams.

Step three is calculating the dry weight of sugar required to produce that amount of carbon dioxide. The following table provides dry weight sugar-to-carbon dioxide ratios for several common priming sugars. These values assume 100% conversion of fermentable sugar to carbon dioxide and ethanol. Also shown is the fermentable sugar composition used to calculate each ratio. Note that the values for honey and DME/wort are approximate because the sugar profiles of these ingredients vary. Also note that dextrose is listed as only 91% glucose because most of the powdered dextrose sold for brewing and beverage applications is glucose monohydrate, which contains about 9% water even when its measured moisture content is zero.

To determine the dry weight of whatever priming sugar you want to use, multiply the sugar-to-carbon dioxide ratio by the carbon dioxided requirement calculated in the previous step. For example, to produce 45 grams of carbon dioxide using table sugar, multiply 45 by 1.94. The result is 87 grams of table sugar on a dry-weight basis.

Here’s where things become approximate: You must know the moisture content of the sugar or syrup used for priming. Table sugar typically contains about 5% moisture, or 95% solids. To obtain 87 grams of sugar on a dry basis, divide by 0.95. The calculation yields 92 grams of sugar from the bag.

Things get trickier with syrups because most do not list moisture content, so you need either a product specification sheet or reliable reference data. Even with specification sheets, you’ll usually find ranges rather than single values. For example, Candico amber candi syrup from Belgium — a sucrose-based syrup — ranges from 78.0 to 80.5 °Brix. Using that range and the 45-gram carbon dioxide target, you’ll need 108–112 grams of syrup. That relatively narrow range contrasts with honey, which typically ranges from 70–88 °Brix and therefore requires 108–136 grams to produce the same 45 grams of carbon dioxide.

Wort is a special case. The solids content of wort is the same as °Plato. For example, to produce 45 grams of carbon dioxide from 12 °Plato wort, we need approximately 139 grams of wort (dry basis) or 1,158 grams of wort. It is important to either weigh wort for priming or convert it to volume by dividing weight by specific gravity.

By the time this answer is published, the holidays will have passed, but the topic remains timely; Holiday Ales are far from the only styles that benefit from using different priming sugars. Hope this information proves handy!