Adding sugar to control alcohol

Measuring SG with a hydrometer

When must ferments, it is turning sugar into alcohol. Last year, our wine was high in alcohol. This year, I think it will be lower and may need a boost. Less sugar in the fermentation equals less alcohol in the wine. 

Trying to control the alcohol content of your wine is not always necessary. Most recipes are designed to make a wine that is in balance and has an alcohol level that is appropriate to the wine’s traditional style.

Wine recipes often call for specific quantities of sugar. But if you are starting with grapes, adding half the sugar that a wine recipe calls for does not give you half the alcohol in the wine. This is because some of the sugar is coming from the fruit itself.

An easy way to get around this is to use this general rule of thumb when attempting to control the alcohol content of a wine:1 pound of sugar dissolved in 5 gallons of must will raise the potential alcohol content by approximately 1%.

“One pound of sugar added to 5 gallons of must will increase the wine’s potential alcohol by 1%.”

The opposite holds true as well.

Controling the alcohol content of your wine

The biggest problem with this generality is that it does not tell you what your potential alcohol level is  before you make any adjustments. If you are following a wine recipe that calls for a specific amount of sugar, it will only get you in a potential alcohol range, not an exact target. This is because the amount of sugar contributed by the fruit can vary.

The best way to adjust the beginning sugar level in your wine’s must is to use a wine hydrometer. Most gravity hydrometers have a Potential Alcohol scale that will tell you how much alcohol the sugar in your wine can potentially make. Knowing this will allow you to control your finished wine’s alcohol level with more precision.

What's the best alcohol level in the finished wine?

The wrong alcohol content can have consequences. Too little and your wine can spoil, too much and it can taste harsh.

The alcohol level of a wine should be at least 8%. Wine needs alcohol to keep contaminants in check. Over time, wines that have 5%-7% alcohol are more susceptible to spoilage and tend to turn brown.

You also do not want your wine’s potential alcohol to be more than 14%. There's a limit as to how much alcohol a wine yeast can tolerate. Shooting for an alcohol level that is beyond your yeast’s ability to ferment can result in either a stuck fermentation or a wine that is too sweet.

The Alcohol by Volume (ABV) is calculated by subtracting the start gravity from the finish gravity and dividing this figure by 7.362. For example, the starting point for our wine last year was 1.100 and if this fermented down to 0.990, the drop will have been 110 points. This divided by 7.362 is 14.94% ABV. In fact, we ended up with a very high alcohol content but not as high as the calculation. 

Raising the specific gravity (SG)

Raising the specific gravity of wine with sugar syrup is a good way to get the SG up to where you need it when making a wine that just needs a little boost. Knowing how much sugar syrup to add to the wine to get from point A to point B on a hydrometer scale is very useful. To do this you need to know the specific gravity of the sugar syrup. 

You can use a wine hydrometer to determine the specific gravity of the sugar syrup you make. Just put the hydrometer in a sample of the syrup just like you would when testing your wine. If the reading goes off the scale, add an equal amount of water and sugar syrup to a sample large enough to fill the cylinder in which you are doing your readings. Then take a gravity reading and times it by two.

As an example, after you added equal parts of water and sugar syrup, let's say you get a reading of 1.110. That would mean that the sugar syrup’s 'actual' SG is 1.220. You double the 'gravity' part of your reading because you cut the sugar syrup by half. 

Once you know the SG of the sugar syrup, raising the specific gravity of your wine with sugar syrup is just a matter of some calculations. 

Let’s say you want to add 6 ounces of sugar syrup that has a specific gravity of 1.300 to a gallon of wine:

A gallon of wine has 128 fluid ounces. You want to add 6 fluid ounces of sugar syrup for a new total of 134 ounces. Now you need to spread the gravity of (220 times 6) over the 134 ounces. So it is (220 X 6) divided by 134. That equals 9.8507. 

Let's make an equation

(Gravity of Syrup x Ounces of Syrup Per Gallon)/(128 + Ounces of Syrup Added) = Rise in SG

or

(220 x 6)/(128 + 6) = 9.85

There is a very good explanation and useful chart on this page. 

So if you are raising the specific gravity of a must with a sugar syrup that has a specific gravity reading of 1.220, and you add 6 fluid ounces of that syrup to each gallon of homemade wine, then the specific gravity of that homemade wine would be raised by 9.85 points on the gravity scale. For example, if the wine has a specific gravity of 1.060, the new reading would be 1.06985. You could round it to 1.070.  That yields a potential alcohol figure of 9.2. That's perfect!

I have ordered a book that many call the bible of home winemaking:  First steps in winemaking. It apparently covers this topic very well. 

Hydrometer Chart

Specific Gravity (SG)	Potential Alcohol (PA) % by Volume	Amount of Sugar Per Gallon
1.010	0.9	0 lbs. 2 oz.
1.015	1.6	0 lbs. 4 oz.
1.020	2.3	0 lbs. 7 oz.
1.025	3.0	0 lbs. 9 oz.
1.030	3.7	0 lbs. 12 oz.
1.035	4.4	0 lbs. 15 oz.
1.040	5.1	1 lb. 1 oz.
1.045	5.8	1 lb. 3 oz.
1.050	6.5	1 lb. 5 oz.
1.055	7.2	1 lb. 7 oz.
1.060	7.8	1 lb. 9 oz.
1.065	8.6	1 lb. 11 oz.
1.070	9.2	1 lb. 13 oz.
1.075	9.9	1 lb. 15 oz.
1.080	10.6	2 lbs. 1 oz.
1.085	11.3	2 lbs. 4 oz.
1.090	12.0	2 lbs. 6 oz.
1.095	12.7	2 lbs. 8 oz.
1.100	13.4	2 lbs. 10 oz.
1.105	14.1	2 lbs. 12 oz.
1.110	14.9	2 lbs. 14 oz.
1.115	15.6	3 lbs. 0 oz.
1.120	16.3	3 lbs. 2 oz.
1.125	17.0	3 lbs. 4 oz.
1.130	17.7	3 lbs. 6 oz.

Bottling the wine

As we really didn't have much yield, we didn't expect much in the results. But we are pleasantly surprised by our Rondo 2020. The specific gravity reached 0.99 and Alex has bottled the wine despite not having achieved good clarity. He's filtered it a second time, a slow process but manageable with 4 bottles of end products.  

Our start SG was 1.10 and our finish is 0.99 so our finish alcohol content is 14.9%.  A bit on the strong side, but the taste and colour are very acceptable. Now we wait six months and taste again. Right now it has a fruity and slightly tart mouthfeel. But it's not unpleasant. 

"Wine is sunlight, held together by water." - Galileo Galilei

I suppose we are now among the crazy Irish trying to make wine in the west of Ireland.  

The second stage

We racked the wine into the demijohn and corked it with the oyster farm cork with fermentation airlock. It smelled very good and Alex said he tasted it yesterday and it was good. But the specific gravity was 1.02 so we have a little ways to go to get to 0.99. It might be just a little cool in the pantry area. It will remain there for about two weeks before stabilizing. 

There is not much more to this stage so we'll just wait and hope it continues to ferment a little more. Meanwhile, the remaining grapes, those that were way behind ripening, are not ready to pick and eat. 

So what's next in making our wine

Hydrometer suspended in grape juice

The wine must has to ferment for about 2 weeks in the first stage. When fermentation stops, you have to test the specific gravity. When making wine, the Start Gravity should be 1.070 (normal finished ABV will be 10.5%) to 1.090 (normal finished ABV will be 13%). Finish Gravity should be 0.990 (for dry wines) to 1.005 (for sweet wines). 

I've seen many recommend that wine should be fermented down to dryness. If you like a sweeter wine, you can then add sugar or grape juice at the end to reach your preferred sweetness. It is a dangerous business stopping the fermentation early. 

So the hydrometer is probably the most essential piece of equipment to make wine with success. I've ordered a spare as I can imagine that it's pretty easy to break. I've also read about how to read the hydrometer properly. You have to make sure your hydrometer is floating freely and not stuck against the cylinder. You read at the bottom of the meniscus not the top (I remember that from chem class). It measures the Specific Gravity (SG) of the liquid being fermented. This will then in turn give you a guide to the Alcohol by Volume (ABV) you will be able to produce. The hydrometer is used throughout the fermentation to ensure sugar is being converted into alcohol. As more sugar is converted to alcohol, the SG will fall.

The Alcohol by Volume (ABV) is calculated by subtracting the start gravity from the finish gravity and dividing this figure by 7.362. For example, the starting point for our wine is 1.100 and if this ferments down to 0.990, the drop will be 110 points. This divided by 7.362 is 14.94% ABV. That should kick a punch. 

You have to make certain the fermentation is complete and stopped at the right time. Sometimes fermentation slows down or stops too early. A stuck fermentation is one that falls short of reaching the expected final gravity, and as with many things brewing, the term is relative. A wine that stops at 1.000 probably suffers more from poor instrument calibration than it does from stuck yeast. A 1.100 wine that stops at 1.045, though, still has a way to go and needs some help.

There are tricks that one can use to restart the fermentation process. One is temperature. If the hydrometer is placed in water at 20°C, it will read 1.000.  Most people only use the hydrometer as a guide but if you want to be really accurate then this should be done with a liquid temperature of 20°C. If the liquid is 5°C higher then add 0.001 and similarly if its 5°C lower then delete 0.001.

Warming up the must is probably the most reliable way to restart a stalled fermentation. Some yeast strains are more temperature-sensitive than others and may require some warmth to complete the job. Some strain are famous for refusing to budge until they are warmed as high as 95°F (35°C). Some British yeasts are stubbornly flocculent; it’s worth giving the must a good swirl a couple of times a day just to keep the yeast cells in suspension until they’re done.