Moley wrote:There are very few cases where you can actually measure an OG for wines with a hydrometer.
For example, with juice wines going straight into a DJ you’ve got to leave headspace at the start or it will overflow. If you measure an OG but then top up with water when fermentation has quietened down, that OG is cocked up and you have to correct for volume changes. That also means that you have to calibrate some fermenters. 5 litre water bottles will hold exactly 5 litres to the base of the neck but it’s useful to mark them off with sticky tapes or permanent pen at 4, 4.25, 4.5 and 4.75L. Gallon DJs are rarely exactly one gallon, they vary, a few of mine have been measured and labeled and seem to average around 4.75 litres.
If you started with 4L in a 5L bottle and later top up with water, multiply your gravity points by 4/5, for example (1.) 100 x 4 / 5 = (1.) 080
With fruit wines it can get very tricky, it might take a few days to extract all of the fruit sugars so your initial gravity reading will be too low, and then if you start fermenting on the pulp it stuffs up the maths completely.
First off, let’s go back to how to read a hydrometer.
Hydrometer readings are always given to three decimal places even if the last digit is a 0, so there’s no such reading as 1.05, that should be 1.050
Ignore the 1. and think of 1.000 as zero, so that’s 50 points
1.110 is 110 points, 1.036 is 36 points and 0.995 is 5 points below zero.
36 points is an important one, because 100g of sugar in 1 litre gives 36 points.
If you buy fruit juices, the sugar content is printed on the carton, so let us consider a Wurzel’s Orange.
One litre of white grape juice might contain 150g of sugar, one litre of orange juice might contain 100g of sugar, you might add 850g of granulated sugar and ultimately end up with a 5 litre brew.
150 + 100 + 850 = 1100g sugar in 5 litres = 220g / litre
100g / litre gives 36 points, so 220g gives 2.2 x 36 = 79 points. Your OG is 1.079
If you started that at 4 litres your hydrometer would say 1.099, which is why I said you have to adjust for volume changes if you add more water later on.
If you want an OG of 1.090, work it backwards:
90 / 36 = 2.5 so you need 2.5 x 100 = 250g sugar per litre x 5 litres = 1250g, and there is 250g in the juices so you need to add 1000g.
If you are using fresh fruits, the same principles apply, but you need to be able to calculate the sugar content of the fruit. There are various tables around on the web but these are a few examples I’ve collected. For dried fruits, read the packet.
Apple (Cooking) 9%
Apple (Eating) 12%
Apricot 8%
Banana 17%
Blackberry 7%
Blackcurrant 8%
Blueberry 8%
Bilberry 6%
Cherry 12%
Cranberry 4%
Damson 9%
Elderberry 11.5%
Gooseberry 8%
Grape 15-20%
Grapefruit 6%
Greengage 11%
Guava 7%
Hawthornberry 8%
Kiwi 14%
Loganberry 5%
Lychee 17%
Mango 11%
Medlar 11%
Orange 11%
Papaya 8%
Passion Fruit 8%
Peach 9%
Pear 10%
Pineapple 13%
Plum 10%
Pomegranate 13%
Raspberry 7%
Redcurrant 6%
Strawberry 6%
Tangerine 7.5%
Whitecurrant 5.5%
Lemon, Lime, Rhubarb - too low to bother about.
Digressing for a moment, when calculating alcohol by volume you divide the gravity points dropped by a factor. I learned that to be 7.36, others use 7.46 so to avoid argument I’m going to split the difference and call it 7.4
So for example, you are making 5 litres and using 1kg blackberries + 500g elderberries
You want a wine of 14% abv so you’re looking for a gravity drop of 14 x 7.4 = 104 points
Most wines will finish around 0.990 (10 points below zero) so we want an OG around 1.095
95 / 36 x 100 = 264g sugar required to the litre, x 5 = 1320g total.
1000g blackberries x 7% = 70g sugar
500g elderberries x 11.5% = 58g sugar
70 + 58 = 128g and I usually guestimate on 90% extraction = 115g sugars from fruit.
1320 - 115 = 1.2kg to add.
Simple
oldbloke wrote:Well, that's the fruit/sugar list.
I find the rule of thumb 20g/l=1% is good enough (90g/gallon=1%, 1350g/gallon=15%)
I generally go for a total sugar of about 1250g
You have 4lbs plums at 10% sugar, about 1820g. Making 2 gallons, that's a bit over 900g each. So you want to add about 350g each, 700g total, to get to around 13-14%. The raisins will add a bit, but then you'll lose some when you rack and top up with water. It's all a bit handwavy anyhow.
gregles wrote:oldbloke wrote:Well, that's the fruit/sugar list.
I find the rule of thumb 20g/l=1% is good enough (90g/gallon=1%, 1350g/gallon=15%)
I generally go for a total sugar of about 1250g
You have 4lbs plums at 10% sugar, about 1820g. Making 2 gallons, that's a bit over 900g each. So you want to add about 350g each, 700g total, to get to around 13-14%. The raisins will add a bit, but then you'll lose some when you rack and top up with water. It's all a bit handwavy anyhow.
Just trying to follow this and I am getting confused. I am getting old though...
1 pound = 454 grams. 10% sugar would be 45.4grams so 4 pounds would give 181.6grams sugar. Split between 2 demijohns would give around 90 grams each?
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