When to harvest?

The busiest and most crucial period in our vineyard has begun. I have seen grapes changing colour and so veraison is underway. But how do we know when is the optimal time to pick? And what should we be doing now to prepare for harvest?  

Most winegrowers in addition to the obvious signs, their “instinct”, and the interest of wild animals especially birds, also take into account measurements of sugar, tartaric acid (TA) as well as the pH of the grapes. Since these measurements differ for different varieties and the micro-climate of each vineyard, each winegrape grower should know her ripe grapes' optimal values. According to some literature, the optimal levels for red wines are Brix: 22, TA: 0.75, pH: 3,4; and for the white grapes Brix: 20, TA: 0.7 and pH: 3.2. This I will have to develop as I monitor annual harvests. Eventually, I'll need to buy a pH and TA tester. 

I have not tested before and, as a result, we lost our first tiny harvest to birds, our second harvest was spot on and our third harvest was too early. So I finally bought a refractometer, one of the most common tools for winegrowers to measure the amount of sugar in the grapes. I have used it to measure the sugar content at the various stages of wine maturation and it's pretty easy. What I need to do is start measuring now so that I have an indicator of increasing sugar content. Here's a good article to refresh knowledge about how to read a refractometer and more. 

Aside from monitoring grape ripeness, I will also be monitoring the weather and the appearance of diseases and pests. Botrytis becomes especially problematic after the grapes attain 8% sugar content. As we are an organic and natural vineyard without use of pesticides or other chemicals, I will have to remove anything that is affected immediately. That requires daily vigilance in the vineyard from now until harvest. 

I'll have to prepare all the tools and equipment as well and clear space for working. We really need a shed for the winemaking, as we've outgrown the house. 

Meanwhile, Spain has reported its earliest harvest ever. 

Correcting the sugar content

Looks like we messed up. 

Our red must has tested at just over 1.008 on the hydrometer and 5 on the Brix scale. That won't get us to the right alcohol content - too low. We should have added sugar to the must at the first stage but we didn't.

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).

Alex made a simple sugar syrup dissolving sugar in boiled water. We have to wait for it to cool to room temperature. 

Now we have to figure out how much syrup to add. Because I had to dilute the sugar solution by half to get the hydrometer to read the SG, the specific gravity of the syrup is 1.110 x 2  or 1.220. 

So to increase the SG to where the potential alcohol would be sufficient, we'd have to add 40 oz sugar per gallon or 2.5 lbs per gallon. That would be 1 l of water or 1.5 l of syrup. (Alex did the maths.)

Just as a note to self:  3 kg water plus 3 kg sugar = 1 demijohn.

So we expanded our two demijohns to three with the sugar syrup and must (stirred to keep the yeast equal) divided equally among the three. I tested the SG of the resulting must and it read SG 1.070. That should get us to over 9% ABV. 

Curiously, I just measured the SG of the Solaris must, and it, too, reads 1.008. Not surprising as it started out at the exact same SG as the Rondo must. So we'll have to repeat the procedure for the white. 

So we have 1.5 l of Solaris must, measured by weight. So if we need 40 oz sugar per 3.78 l above, we need:

40/3.78 = x/1.5 = 15.9 or 16 oz of sugar. We added 16 oz of sugar dissolved in 16 oz of water to the 1.5 l of must and essentially doubled the volume. The SG read 1.082, a little higher than the red but perfectly fine. 

Let's hope we have restarted the fermentation. At least we now have 1/3 more wine to bottle. 

Here are 10 more things that can go wrong in fermentation. 

https://www.brewersfriend.com/abv-calculator/ 

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.