Wine Learning Centre
Winemaking is an ongoing learning process. Our learning centre has articles that will help you understand and master some of processes required to make good wine.
How to use a hydrometer
What is a hydrometer?
A hydrometer is an instrument used to measure the specific gravity (or relative density) of liquids; that is, the ratio of the density of the liquid to the density of water.A hydrometer is usually made of glass and consists of a cylindrical stem and a bulb weighted with mercury or lead shot to make it float upright. The liquid to be tested is poured into a tall container, often a graduated cylinder, and the hydrometer is gently lowered into the liquid until it floats freely. The point at which the surface of the liquid touches the stem of the hydrometer is noted. Hydrometers usually contain a scale inside the stem, so that the specific gravity can be read directly. A variety of scales exist, and are used depending on the context.
How a hydrometer is used in winemaking
When you mix your wine kit and before you add the yeast you will want to take a hydrometer reading. Your wine will now contain a fair amount of solids and sugar from the juice so you will get a fairly high gravity reading. As the fermentation proceeds the yeast will consume the sugar and produce alcohol which has a lower specific gravity than water. So this lets you monitor the fermentation. If you take a reading and you get a lower specific gravity you know the fermentation is progressing. Gravity readings are also important when it comes time to stabilization and clearing of your wine. Your wine kit manufacturer will instruct you to do different steps bases on the specific gravity of your wine.
Filtering your wine
Although it's not entirely necessary we recommend that you filter your wine. Wine will gradually clear on it's own but this could take several weeks if not months. Filtering your wine will minimize deposits of yeast in your stored wine and make it more stable. There are a few different filtering systems used in winemaking. The Buon Vino MiniJet is popular with small volume winemakers but there are other types such as cartridge filters and the EuroFilter.