The David J. Schryver
Winemaking Computations Primer

As previously
mentioned, I found myself searching all over to get advice on
making certain computations needed in the winemaking
process. This page is a brief look at that.

Adding
sugar to the must if your starting sugar level (Brix) is too low

Background: 
Most winemakers
agree that you should start the grape winemaking process
with a must of between 18^{o} and 21^{o}
Brix. The degrees of Brix is basically the
percentage of sugar by volume of your must or juice.
For example, 20^{o} Brix means that 20% of the
volume of your juice is sugar. Some people
rightfully believe that if you like a drier wine, you
should start on the lower end of that range. If your
tastes are sweeter, start on the higher end. After
fermenting your wine, if it is too dry, you can always add
sugar, after treating with Potassium Sorbate to inhibit
the yeast. If it is too sweet, however, the only way to
reduce the sweetness is to water it down, which also
reduces the alcohol level, the acidity and the body.
For this computation, we need to know some
numbers. You need to know the Desired Brix, which I
will call the DB. That is the number, probably
between 18 and 21 that we discussed in the previous
paragraph. You also need to know the Starting Brix,
or SB. This can be found by using a refractometer or
hydrometer or will be provided by the business where you bought your
supplies. If you measure your Starting Brix,
remember to stir the must well. Simply dipping into the
juice and extracting a drop or two will probably result in
a lower than accurate reading because the majority of the
sugar is lower in the juice. This could cause you to
add more sugar than desired.
If your SB is equal to or more than your
DB, you are home free. You don't need to add
sugar. That usually isn't the case. You will
also need the size of your batch ... 3 gallons, 5 gallons,
whatever! If you have a partial gallon amount, a
reasonable estimate will work. For example if you
have about a quart over a 5 gallon carboy, call it 51/4,
or 5.25
We will also note that .125 pounds of sugar (1/8 pound)
will raise 1 gallon 1 Brix or degree. One
ounce is .0625 pounds. When I originally researched
this, I found that most sites use the conversion of 1 pound
of common table sugar is about 2.25
(21/4) cups. I used this for several years.
At some point, I used this conversion when I needed 2.7
pounds and realized I was going to come up short with a
3pound bag. I ran an experiment with a 4pound bag
from a different manufacturer with the same results.
I now use the conversion of 1 pound = 2 cups and it is
more accurate. You can also use corn sugar or honey,
but those values are different. The information in
this paragraph is basically a set of facts which you don't
really have to worry about. 
Calculate: 
Get your
calculator and follow these steps ...
 DB  SB ... in other words, subtract your Starting
Brix from your Desired Brix ... this will give you the
number of degrees of Brix you need to raise your must.
 Multiply this value by the number of gallons of your
must.
 Now divide this by 8 ... this gives you the number
of pounds of sugar you need
 Multiply this value by 2 and you have the number
of cups of table sugar you need to add to your must or
juice.
Obviously, if you need more than the amount in the bags
you are using, save yourself some time. Use a whole
bag and only convert the balance.


Treating
with Calcium Carbonate to lower TA

Background: 
The TA (total
acidity) of your must or juice should be between 0.70 and 0.85%. If it is higher than this, you will probably want to
treat it to lower it. In my research, I found several points
that are important. First of all, the TA of a must will drop
about 0.12% in the normal fermentation process. Secondly, if
you also cold stabilize, which is highly recommended in higher
acid situations, the TA will drop about 0.2%. Having said
that, my personal preference is to have the 0.70 to 0.85% range
without these other considerations.
The first time I treated with Calcium Carbonate, my
package had no instructions. I researched online
and found that 2.5 grams of Calcium
Carbonate will reduce1 gallon of must by 0.1% TA. Since we live in
the USA, 2.5 grams probably doesn't mean much to most of us.
Some basic math converted this to about 1 teaspoon.
The second package of Calcium Carbonate I bought had
instructions on the bag. It stated "1/2 teaspoon of
Calcium Carbonate will reduce 1 gallon of must by 0 .1% TA".
Because of this disagreement, I went online to see what I
could find. One website agreed with this 1 teaspoon
figure. Another said that 1 tsp = 2.1 grams, which
implies the figure is slightly less than 1 teaspoon.
I also consulted with two friends with considerably more
winemaking experience and expertise than I have.
They agreed with the 1 teaspoon number. Bottom line,
follow the instructions on the package. If there
aren't any, go with the 1 teaspoon per gallon per .1%
figure.
There are some other points we need to consider. First of
all, treating with Calcium Carbonate will raise the pH of your
must. For each 0.1% you drop your TA, you will raise your pH
by 0.1. Since you shouldn't elevate your pH to over 3.5, that
can also become an issue. For example, if your starting TA
is 1.05 and your pH is 3.2, lowering your TA to 0.85% will raise
your pH to 3.4 which is perfectly fine. However, if your
starting TA is 1.05 and your pH is 3.4, lowering your TA to 0.85%
will raise your pH to 3.6 which is too high. In this case,
you might want to add sugar water or combine these two
techniques. One last note ... it is generally recommended
that you not attempt to use Calcium Carbonate to drop the TA by
more than 0.3%. 
Calculate: 
This one is quite
easy. For each unit of Calcium Carbonate you add
per gallon, whether it be 1/2 teaspoon or 1 teaspoon, simply subtract 0.1 from the starting
TA. Also, add 0.1 to the starting pH. 

Adding
sugar water to lower TA

Background: 
Another
method for reducing the TA in a must is by adding sugar
water. Assuming there is no acid in your water, this
method can be used without affecting the pH of your
must. The important things to consider here are:
 most people will prefer to use bottled water for
this, but if you live in the country and have a
healthy well, that will work fine
 it is recommended that you not add more than 15%
water by volume to your must ... some sources say 10%
...
for most grape varieties. However, certain
varieties such as Catawba and Concord can tolerate an
addition of up to 50%. The more you add, the
less body you will have.
There are two computations you will need here. 
Calculate
water: 
 Multiply the number of gallons in your must by the
current TA. Remember to use a decimal if you
have a partial gallon and if you already treated with
Calcium Carbonate, use the reduced TA value.
 Divide this number by the desired TA, probably
.85. You don't want to reduce it any more than
you have to. This number is the number of
gallons you will have after adding the water.
 Subtract the number of gallons you started with from
this ... this will give you the number of gallons you
will need to add. Make a note of this
number. You may need it later.
 Now multiply this by 128 ... there are 128 ounces in
a gallon, so this number is the number of ounces of
water you need to add.
Before actually adding this, you should compute to make
sure it isn't an excessive amount. In step 3 above,
we noted that you will need that number later.
Divide that number by the number of gallons you started
with. This should not exceed .15, or 15%.
Remember, some prefer to not exceed 10% and Catawba and
Concord can handle up to 50%. 
Calculate
sugar: 
 Take the Starting Brix (back at the beginning of
this page ... probably between 18 and 21) and multiply
this by the number of gallons of water you
added. Again, refer back to #3 above
 Divide this number by 8
 Multiply this number by 2 ... this is the number
of cups of table sugar you will need to add to the
must to make up for the water you added


Adding
a set amount of sugar water to lower TA

Background: 
I have
also found myself in a situation where I wanted to add a
set amount of sugar water and then determine what TA this
would take me to. 
Calculate: 
 Multiply the number of gallons in your must by the
current TA. Remember to use a decimal if you
have a partial gallon and if you already treated with
Calcium Carbonate, use the reduced TA value.
 Express your new total volume as a decimal ... for
example, if you want to add 10%, one gallon is 128
ounces. 10% of this is about 13 ounces ... the
total would be 1.1 gallons ... simply multiply
this by the number of gallons you started with.
 Divide the number you got in step 1 by the number
you got in step 2 ... this is your new TA


Adding
acid blend to raise the TA

Background: 
Occasionally,
especially during dry summers, you may encounter a
situation where the TA is less than .70%. In this
scenario, you might want to add acid blend to raise the
TA. This is actually a fairly easy
computation. You will need to know the Starting Acid
Level, which we will refer to as the SAL. The
Desired Acid Level, or DAL, will probably be .70. 
Calculate: 
 Subtract the Starting Acid Level from the Desired
Acid Level ... DAL  SAL
 Divide this number by .15.
 Multiply this by the number of gallons of must you
have.
 This will give you the number of teaspoons of acid
blend to add.


