Author Topic: Newbie question about SG  (Read 423 times)

Offline cbeener

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Newbie question about SG
« on: January 19, 2018, 09:32:40 PM »
Hello all, I have just started my venture into homebrew and I am beyond excited.  This will be a silly question for most but I figure I can ask you experts without feeling like an idiot.  Why are gravity readings necessary in the brewing process besides that they tell you when fermentation is done?  I get that its nice to know but what can be done if your gravity readings are off?

Thank yall

Offline klickitat jim

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Re: Newbie question about SG
« Reply #1 on: January 19, 2018, 10:07:43 PM »
What do you mean by gravity readings are off? Will help get you the right answer

Offline ethinson

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Re: Newbie question about SG
« Reply #2 on: January 20, 2018, 12:11:16 AM »
"besides telling you when fermentation is done" ? Well... that's pretty damn important. 

Your original and final gravities allow you to calculate your alcohol percentage, where you finish can help you with mash efficiency and your starting can tell you your hop utilization, so I'd say it's all pretty important.

If by "off" you mean your gravities don't match the recipes estimates than that's when you adjust your recipe.  It may not help you with that batch, but with the next batch.  Starting too low? Maybe the mash wasn't good.  Finishing too high? Maybe the yeast wasn't healthy, etc etc.  Gravity tells you a lot about fermentation characteristics, but it might take a couple batches to see the change.
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Offline ASLO

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Re: Newbie question about SG
« Reply #3 on: January 21, 2018, 03:23:50 AM »
Knowing your SG is also important for determining how much yeast to pitch. Also, in addition to telling you when your fermentation is complete, your final gravity (along with the anticipated attenuation of the yeast strain that you used) can help you gauge how much priming sugar to use at bottling (if you are bottle conditioning). For instance, if you fall a little short of your anticipated attenuation, you may want to scale back the priming sugar to avoid over carbonating.

Offline cbeener

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Re: Newbie question about SG
« Reply #4 on: January 23, 2018, 03:17:46 PM »
Ok thank you for the information.  Everything yall are saying makes more sense now that I think about it.  By "off" I meant for the recipe.  Ill keep taking them and tweaking to make a better beer!

Offline Big Monk

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Re: Newbie question about SG
« Reply #5 on: January 23, 2018, 03:32:45 PM »
For All Grain recipes, gravity readings tell you much about things that may or may not have happened in the mash.

For Extract recipes, I'd say that they are less important pre-fermentation.

For fermentation, gravity readings are important for knowing where you are at in the fermentation process.
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Offline klickitat jim

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Re: Newbie question about SG
« Reply #6 on: January 23, 2018, 03:46:25 PM »
Ok thank you for the information.  Everything yall are saying makes more sense now that I think about it.  By "off" I meant for the recipe.  Ill keep taking them and tweaking to make a better beer!
The suggested FG is rarely hit perfectly. Take it as an estimate. If you are way off something may be fubar. Give lots of details and we can help diagnose.

Offline hopsindahood

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Re: Newbie question about SG
« Reply #7 on: January 25, 2018, 12:19:12 AM »
How are you taking your gravity readings? If you're using a hydrometer, carry on. If you're using a refractometer, remember that it is not accurate when alcohol is in the solution. There are calculators that you can use to determine the correct gravity reading when alcohol is present, but I find it easier to use a refractometer for OG and a hydrometer for FG. When you are trying to determine if fermentation is complete, I use a refractometer, since it only "wastes" a drop or two of beer. Since I'm only looking for a change in gravity and not the actual reading, this works fine. I take a sample and write down the number. Wait 2-3 days and take another sample and check it again. If the reading changed, then you know something is still happening. Wait another 2-3 days, take another reading and repeat as necessary. I've experienced a wide range in fermentation times depending on the yeast, OG, temperature, etc. Don't assume 2 weeks is always the fermentation time. I'd also recommend calibrating your refractometer regularly. Mine drifts quite a bit in between uses, for some reason.