OG / SG Calculations

Jim -

I think your calculations are correct, or at least, near enough for your purposes. At 1.124 you have high enough S.G. that you might have difficulty getting fermentation started. Assuming that wasn't a problem, I think you can treat the 28 gallon batch (after you add the last 2.5 liters of water) as if it started at 1.113.

Doug

The confirmation is very much appreciated here Doug. On the recommendation of a friend I used gervin no.3 (champagne style) rather than no.2 (montrachet red style) yeast and it has coped admirably. I am glad I trusted his wisdom in the absence of my own!

I will proceed with that estimate in mind :D

Jim

moment and due to a schoolboy error I made just

I had to hold back 2.5 litres of water

recipe is all in the correct ratios.

Gravity at the start would have been

Jim, The difference between 28 litres and 25.5 litres is 2.5 of water. But, let say that instead of water, with an SG of 1.000, you had to use another must with an SG of, let say 1.080. What then would have been your solution?

Guy

Guy

Wow, I don't know, it took me while to figure out that I needed to ignore the

1.000 in my calculations below and add it back at the end ;) I just juggle numbers till it looks right!

The best algorythm I could come up with was this, I don't know if it is right but it looks likely?

(((original SG-1) * number of litres at SG)+((added SG-1) * number of litres at SG)) / total litres in fermenter at end)

• 1

so in the original example modified to use an added solution at an SG of 1.080:

((3.162 +0.2 )/28)+1 FINAL SG 1.120

Does that sound about right to you? It looks like it might be to me.

An alternative which may only give different results because of liberties I took with rounding.

((original SG-1) * (number of litres at this SG/total number of final litres) + ((diluting solution SG-1) *(number of litres at this SG/total number of final litres) )+1 = estimated starting diluted SG

so...

0.124 * (25.5/28) + 0.080 * (2.5/28)

• 1

= 0.112 + 0.007

• 1

FINAL SG 1.119

My head is too fuzzy after thinking all that to perceive if it is really logical or different at all! They could both be wrong ha ha here in England it is 3.04 am so forgive my waffle !

Jim

moment and due to a schoolboy error I made

that I had to hold back 2.5 litres of water

recipe is all in the correct ratios.

Specific Gravity at the start would have been

Sorry, I horribly misused conventions above. By FINAL SG in my results I meant predicted 'diluted OG'.

Jim

1.000 in my calculations below and add

but it looks likely?

at SG)) / total litres in fermenter at

took with rounding.

• ((diluting solution SG-1) *(number of

logical or different at all! They could both

moment and due to a schoolboy error I made

that I had to hold back 2.5 litres of

original recipe is all in the correct ratios.

Specific Gravity at the start would have been

Wow! I may be the only one who thinks this, but winemaking is the farthest refuge I could find from complex math!

Well done Jim~!

With beer brewing, you get to play with this sort of stuff a lot if you want to figure your efficiencies and such. The easiest way is to deal with "sugar points." With beer, we usually use gallons... but it should work using liters. You drop off the "1.000" part, so 1.124 becomes 124 points: 124 * 25.5 = 3162 total sugar points (liters). Now you know how many sugar points you have, you can divide by any number of liters to see what the gravity would be then: 3162 / 23 = 137.5 or in your case: 3162 / 28 = 112.9 Then you just put the 1.000 back onto it: 1.1129

Or you can divide by the gravity to see what the volume (liters) would be. Dealing with the points this way makes it easy to, for example, figure how much water to add to reach a desired OG. You have 1.124 @ 25.5 liters and want 1.100: 124 * 25.5 = 3162 total points 3162 / 100 = 31.62 total liters 31.62 - 25.5 = 6.12 liters to add to get 1.100.

So your math was right, but done differently from how I would have done it!

Derric

Well, I thought I posted a reply but it's not showing up, so here goes again - these calculations can be handled well by Pearson square. Jack Keller has an online version at

Use the one in section Solving Adjusted Alcohol of a Blend - it works for any substance where you're mixing 2 different quantities and concentrations, not just alcohol.

Pp

1.000 in my calculations below and add it

but it looks likely?

at SG)) / total litres in fermenter at end)

took with rounding.

• ((diluting solution SG-1) *(number of

logical or different at all! They could both

messagenews: snipped-for-privacy@v33g2000cwv.googlegroups.com...

moment and due to a schoolboy error I made

that I had to hold back 2.5 litres of water

original recipe is all in the correct ratios.

Specific Gravity at the start would have been

at SG)) / total litres in fermenter at end)

That is right by me. A slight modification is to use the original SG without subtracting and then adding 1. Also, I always use the quantity first, so:

25.5 L (1.124) + 2.5 L (1.080) / 28 L = 31,362 L / 28 L = 1.120

That was a good subject Jim

Guy