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Old 01-02-2009, 10:43 PM   #1
HalloweenGod
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Default Specific Gravity? Target Gravity?

Hi, I just have a quick question. I started homebrewing again after a 2 year break and guess I would still call myself a beginner. I have begun looking into all grain brewing and starting to make my own recipes. So here are my two questions.
1) What is the point of the intended specific gravity? And what does it mean?
That question may seem a little vague so maybe the second one will clean up what I am confused about a little more.
2) In the books I am reading when they talk about making your own recipe they always talk about a target gravity. How do you choose a target gravity? I know you just dont pick a gravity and try and hit it. But in all the books they dont explain why and how to choose your target gravity. If this could be explained to me it would make me stop banging my head.

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Old 01-02-2009, 10:56 PM   #2
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Originally Posted by HalloweenGod View Post
Hi, I just have a quick question. I started homebrewing again after a 2 year break and guess I would still call myself a beginner. I have begun looking into all grain brewing and starting to make my own recipes. So here are my two questions.
1) What is the point of the intended specific gravity? And what does it mean?
That question may seem a little vague so maybe the second one will clean up what I am confused about a little more.
2) In the books I am reading when they talk about making your own recipe they always talk about a target gravity. How do you choose a target gravity? I know you just dont pick a gravity and try and hit it. But in all the books they dont explain why and how to choose your target gravity. If this could be explained to me it would make me stop banging my head.
Target Gravity is, typically, the final gravity post fermentation which indicates alcohol content. So, you base your target gravity around your intended alcoholic content. That is the gist of it.

To get there you have to either mash properly or know the fermentability of the extract. You also have to know the eating habits of the yeast. AA% (Apparent Attenuation) is an indicator of that. Strong fermentation temperature control help to facilitate a yeast strains appetite.

There are few references on Extract fermentability but if you look long enough you'll find something.

As for mashing, good thermometers and either well insulated tuns or controlled heating are the ways to hit that right.
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Old 01-02-2009, 11:10 PM   #3
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If you run your recipes through some of the software that's available such as BeerSmith, or BeerTools Pro, your SG's will be calculated for you. The software I mentioned both come with a FREE 30 day trial, so you can decide whether or not to spend the $20 or so to have it for good.

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Old 01-03-2009, 12:28 AM   #4
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Originally Posted by HalloweenGod View Post
Hi, I just have a quick question. I started homebrewing again after a 2 year break and guess I would still call myself a beginner. I have begun looking into all grain brewing and starting to make my own recipes. So here are my two questions.
1) What is the point of the intended specific gravity? And what does it mean?
That question may seem a little vague so maybe the second one will clean up what I am confused about a little more.
2) In the books I am reading when they talk about making your own recipe they always talk about a target gravity. How do you choose a target gravity? I know you just dont pick a gravity and try and hit it. But in all the books they dont explain why and how to choose your target gravity. If this could be explained to me it would make me stop banging my head.
AFAIK, "target gravity" is the target Original Gravity (OG) you're shooting for when you design your grist. Different styles of beer require different OGs - a pale ale that has an OG of 1.060 is different than one with OG 1.038, and you design your grist accordingly.

Thus did I explain my Fuller's London Pride-ish recipe to a pal of mine:
Target an OG of ~1.040.

Grist:

Maris Otter Pale Malt - 80%
British Crystal 55L - 10%
Demerara Sugar - 10%

Bitter with Target and Challenger to ~30 IBU, finish with Northdown and EKG.

Ferment with an English (London) strain.
Now, that allows him to make any size batch - because I specified percentages, not amounts - and moreover design his grist to take into consideration his brewery's efficiencies: it takes more grain to get to 1.040 if your brewery's efficiency is 70% than if it's 80%.

You dig?

Bob
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Old 01-03-2009, 06:34 PM   #5
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Thanks NQ3X that helped clean up my questions, but now oyu have lead to to another one. What is efficiency?

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Old 01-03-2009, 06:40 PM   #6
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Old 01-03-2009, 07:30 PM   #7
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How do you choose a target gravity? I know you just dont pick a gravity and try and hit it. But in all the books they dont explain why and how to choose your target gravity. If this could be explained to me it would make me stop banging my head.
The best way to chose a target gravity is to first chose a style. Then you can visit BJCP Style Guidelines and look up all the various parameters that the style should conform to. Of course, it is easier to use some brewing software such as Beer Tools, Beersmith,or ProMash where you just pick the style and it "knows" the various parameters, and allows you to design a recipe that fits those parameters.

-a.
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