Equipment, gadgets and gizmos every science-minded home winemaker should own

Sooner or later, most serious winemakers conclude that it isn’t good enough to simply follow a recipe blindly. That’s a bit too much like painting-by-numbers. The expression of one’s own skill and artistry makes the difference between an ordinary wine and something uniquely personal. But to do that, it’s necessary to understand a bit about the composition of the wine.

There’s an old saying that if you can’t measure it, it doesn’t exist. So it seems to be self-evident that – if we are serious winemakers – we should understand the measurements that add up to our favorite beverage. If you want to analyze what is right, or wrong, about your wine, you need to do some science. This can be very simple, or a little complicated, or even ridiculous. For the amateur, there are a few options that help to avoid the extremes.

This means we will not be trying to emulate a research lab, but rather use readily available equipment and simplified techniques to discover what we can do to improve our wine. Your home laboratory, which may be as simple as a corner of your winemaking bench, requires a few basics. In broad terms these are measuring equipment, cleaning agents, and records of results.

The handy hydrometer
The hydrometer is the first, and most indispensable, measuring instrument in your home lab. This is a simple device that measures the relative density – or “specific gravity,” usually contracted to “SG” – of a liquid. This figure is important for determining, first, how much sugar is contained in the juice (and therefore what the alcohol yield should be) and, finally, when fermentation has reached completion. The hydrometer consists of a thin sealed glass tube with graduated values marked on it, usually in the form of a strip of paper inside the tube, held in place with a spot of glue.

The tube has a bulbous, weighted bottom. This makes it float upright, but partially submerged, in a liquid (in our case, wine must). The method is to place the hydrometer in a “testing jar,” which is actually a glass or plastic cylinder sealed at the bottom, containing the wine or must to be tested. Ideally, the liquid should be at 60° F when the reading is made. In rough terms, 0.001 should be subtracted from the reading for each 10° F (5° C) below 60° F (15° C), and 0.001 added for each 10° F above 60° F. Since the density of a liquid changes with temperature (density decreases as the temperature rises), the readings will be incorrect if the wine must is at a temperature different from that for which the hydrometer is calibrated. In this case, if the wine must is at 70° F (21° C), a reading of 1.085 actually means a value of 1.086.

It should be noted that some hydrometers may be calibrated at a different temperature (for example, 68° F); before applying a correction factor, ensure that you know what the calibration temperature is (it should be marked on the hydrometer itself). To obtain the reading, the hydrometer is floated (not dropped into) the liquid. It is important to handle the hydrometer with reasonable care, since it is somewhat fragile. The hydrometer is then given a couple of quick twists between the fingers to dislodge any bubbles (which would otherwise affect its buoyancy, again leading to inaccurate readings), and then viewed at the point where the stem breaks the surface of the liquid.

The scale marked on the hydrometer will give the specific gravity. It should be noted that the liquid actually forms what is called a “meniscus” at the edges, where surface tension causes it to climb slightly above the level. The reading should be made at the point where the surface is penetrated, not at the higher level of the sides.