Category Archives: Equipment

Primary Fermenters: What size do you need?

I’m excited about making red wine from grapes this year. It will be my first red, and I needed some new equipment. My largest fermenter has a ten gallon capacity, which is enough for five or six gallons of white wine, but too small for five gallons of red wine. Red wine is fermented on the skins, so you have a larger volume of must than for the same amount of white wine. All that skin and pulp gets forced to the surface, by CO2, forming a “cap.” So the fermenter has to be bigger than the amount of finished wine, to handle the skin and pulp and to contain the cap. How much bigger? A good rule of thumb is that every 5 lb of grapes require 1 gallon of capacity (0.6 kg/liter). For 100 lb (45.5 kg) of grapes, then, I’ll need a 20 gallon (75 liter) fermenter. My local homebrew shop carries 24 gallon (90 liter) fermenters. It’s ok to have a little more room than you need, but it’s a little messy if you’re short so I bought one. All I need now are some grapes!

Calibrating A pH Meter

pH meter, in a champagne glass about a quarter full of 6.86 buffered solution, reads a pH of 6.17 at 31.4 Celsius.To work properly, a pH meter must be calibrated. You do this by preparing (or buying) buffered solutions of known pH and testing the meter against them. My meter uses a two point calibration. It works by immersing the meter in the first buffer solution (pH 6.86 in this case) then reading the pH and temperature values.

You turn a calibration screw until the meter shows the correct pH for the given temperature (the bottle of buffer solution has a table of temperature and pH values). The pH of the “6.86” buffer solution that I’m using is 6.85 at 30 Celsius, the closest temperature on the correction table to 31.4, so I turned the calibration screw to 6.85. That’s the first “point” of the two point calibration process. The second step is exactly the same but with a different buffer solution (ph 4).

I’ll use my new toy – um, important scientific instrument – along with my simple acid titration kit to analyze my oregano wine. Fermentation has been very slow and I’m afraid the pH of the wine has fallen so low that it’s inhibiting the yeast.