Taking a starting hydrometer
reading is one of the most important things you can do when making homemade wine. This is a reading that is taken with a wine hydrometer
before the fermentation has started. It is usually taken at the same time the yeast is added to the wine must.
Having an accurate starting hydrometer reading will not only help you verify that you have an acceptable level of sugar in the wine must, it will allow you to determine the finished wine's alcohol content. This can be done when the starting reading is compared to the finished reading.
The reading is taken on the Specific Gravity scale
. This is a scale based on the weight of water. The weight of the wine is being compared to the weight of water. The more sugar in the wine must the heavier it will be. The more sugar in the wine, the more alcohol the yeast can make.
Keeping in mind its importance, here are the 3 reasons why your starting hydrometer reading is wrong. These are scenarios that I have run across more than once while helping beginning winemakers. In each of these 3 situations the hydrometer reading can be thrown off dramatically.
Too Much Water Was Added: This mostly applies to individuals that are making wine from a wine ingredient kit. These kits typically include around 2 to 4 gallons of concentrate to make 6 gallons. The idea is for the winemaker to add water to make up the difference of the 6 gallons. But on rare occasions a beginning winemaker will add a total 6 gallons of water by mistake giving them an 8, 9, 10... gallon batch of wine. This in turn will give them a very low starting sugar reading on their hydrometer.
Sugars Are Not Mixing Evenly: Before taking a starting hydrometer reading it is important to have the sugars completely dissolved and evenly dispersed throughout the wine must. This is regardless if it is from a concentrate or granulated cane sugar. Not doing so can cause your hydrometer sample to be non-representative of the entire batch. The result is an erroneous reading. For example, if the sugars are not completely dissolved and still hanging towards the bottom of the fermenter, the reading you get from a sample take from the top will be very different from the reading you get when taking a sample through a spigot at the bottom of the fermenter.
Hydrometer Jar Not Being Used: One of the requirements for taking a starting hydrometer reading, is the hydrometer needs to be able to float. If the container being used to hold the sample isn't tall enough, the hydrometer will sit on the bottom. Again, this will give you a wrong reading. This normally happens when the winemaker is trying to use the plastic tube the hydrometer came in to take the reading. This is something I strongly urge against for the simple fact it is not always tall enough to float the hydrometer. Instead, you should be using a hydrometer jar that is designed specifically for this purpose. It is more than tall enough and has a sturdy base so you can keep the wine sample steady and vertical while taking the reading.
These are by far the 3 most common reasons. If you think you have a starting hydrometer reading that is wrong, it is probably because of one of these three. There are other reasons as to why a hydrometer reading might not be completely accurate, such as not having your eye-level even with the surface of the wine, but these are the 3 "big ones". Avoid doing them and you'll be sure to have dependable readings.
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.