Sunday, October 3, 2010

Not realising the gravity of the situation

You can measure the amount of sugars in a solution by measuring its gravity using a hydrometer. If you make a note of the gravity at the start of a fermentation process and then remeasure it at the end you can find out how much the sugar content has decreased. Since the sugar is turned to alcohol by the action of yeast you can use some complicated maths (or simple lookup tables) to figure out how alcohol the resultant solution has. And if your brew consists entirely of fermentable sugars you can use the Original Gravity to estimate how alcoholic the end result will be.

I was using this over the weekend when I was making a hop-free sage ale. Instead of using a malt extract I decided to work on my mash technique and extract the sugars from 1.5kg of grain instead. Once I'd mashed & sparged the grains I boiled the resulting mix up for an hour or so with an ounce of sage, 2 ounces of liquorice root, 3/4 kg of brown sugar and some marjoram (this wasn't in the recipe but there was a mix up at the greengrocers). This produced about 8 litres of a wort with a gravity of around 1050 - enough to produce about a 5% by volume solution. I wanted 10 litres so I made it up with a mix of sugar & water to keep the sugar content up. Once that cooled I pitched the yeast and added an extra ounce of fresh sage leaves to add extra flavour and sage goodness.

After a bit more reading up it turns out that a hydrometer reading is very dependent on the temperature of the brew. I've been measuring gravity at temperatures hot enough to hurt, and this will apparently decrease the reading significantly. After compensating for temperature the OG of my wort was around 1060, leading to a brew that should be about 6.5% alcohol by volume. Add in the extra alledged intoxicating effects of sage and this should be a brew to treat with caution!

I've also started drinking the wheat beer & have sampled the ginger beer. The wheat beer is a bit bland and home-brewey, but the ginger beer has a nice dry gingery burn with a slight clove aftertaste. I was quite impressed, but Liz asked when i was planning to brew something that she would like. Ouch...

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