Does anyone else only take a pre-boil gravity?

For probably my last 5 batches or so, I've only been taking a pre-boil gravity reading. As long as I'm not adding DME and hit my volume into the fermenter (which is the case 90% of the time) I don't see the point. I used to take both, but the numbers always came out, save MAYBE a point. Any thoughts on this? The way I see it, it's another few ounces of beer in my glass. :rockin:

whatsleftofyou said:

For probably my last 5 batches or so, I've only been taking a pre-boil gravity reading. As long as I'm not adding DME and hit my volume into the fermenter (which is the case 90% of the time) I don't see the point. I used to take both, but the numbers always came out, save MAYBE a point. Any thoughts on this? The way I see it, it's another few ounces of beer in my glass. :rockin:

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That's what I've been doing too most of the time, too. I mean, if I've hit my preboil gravity with 7 gallons, then I HAVE to hit my post-boil gravity with 5.25 gallons. The sugar is in there- it can't just go away.

Maybe it's just a Yooper thing?

I only take a Post-boil gravity. If I miss my numbers so bad I have to add DME, ....well, that just doesn't happen anymore.:rockin:

I have been in the habit of taking the pre-boil gravity measurement lately, and I'll tell you why:

1) I make a lot of fine-tune adjustments to my system, and I vary the water/grist ratio of my mash, depending on the beer style. I also opt for mash out and switch back and forth between fly sparge and batch sparge, depending on the system setup that I'm using that brewday. It's good to get an idea of what my efficiency is.

2) If you know your pre-boil gravity, you can make adjustments to your hopping rate accordingly. One time I got 10% BETTER efficiency than I was planning, so I had to up my hopping charges to be sure that I'd hit my IBU's.

3) In the chaos of cleaning and chilling, I usually forget to take a post-boil reading. Like was said, if you at least have a pre-boil reading, the post-boil reading shouldn't be a surprise - the sugars don't evaporate!

the sugars don't evaporate but the water does. i would think this would make it heavier because there is less water for the sugar to be in so wouldnt it be more concentrated and more heavy?

I don't usually take any gravity readings any more, unless I am making an "unusual" beer for my setup.

I take post-boil. If I hit what I wanted (which I do) then cool. If I don't hit what I want, well -- that hasn't happened yet.

I do take preboil and postboil for someone else brewing with my equipment. Just because there are so many variables (crush, grain, recipe formulation, etc) that they don't get the same efficiency that I do.

I don't take pre-boil readings, either. But that's because, like Sly, I'm a rebel who lives on the edge . . . .

I takes both.

Almost always do a pre boil, the last brew I skipped it and of course I missed my FG numbers by a bit more than I like. First miss in a long time, it was not a good brew day.

Hopefully the end product will be good, first time back to liquid yeast in a long time.

I take both and find a difference in both. If you are boiling off water you will have a higher OG. I take both just for consistency sake. To see how I am maintaining efficiency throughout my process. I feel I can more accurately adjust my methods if I have a fuller picture of what is going on in my process.

Tinga said:

the sugars don't evaporate but the water does. i would think this would make it heavier because there is less water for the sugar to be in so wouldnt it be more concentrated and more heavy?

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The gravity reading will be different, you're right. My point was that if you know your pre-boil gravity, then you can easily calculate your post-boil gravity without having to directly measure it.

SG, OG, FG all the time, every time. Might be geeky but............. I can keep a good track of my extraction efficiency, boil efficiency and attenuation.

i take pre boil readings, but only of the last runoff to see if i am over sparging..... i have typically relied only on postboil readings because i fear that preboil readings may not tell me anything accurate if the later runnings have not fully mixed with the early runnings due to stratification. its also still usually so hot that the cooldown takes to long for me... i just don't mess with it, tho it is probably good practice, as more data is always a good thing.

I take a refractometer reading for an idea of where I am pre boil.
Then I do a formal SG check with my hydrometer after the boil. I do it after cooling with the wort remaining in the kettle after I've filled my carboy.

If you only do pre-boil gravities, you don't really know what you put in the fermenter. You know approximately what you have, but unless you boil off EXACTLY the same volume each time, it's only an approximation.

L

jldc said:

If you only do pre-boil gravities, you don't really know what you put in the fermenter. You know approximately what you have, but unless you boil off EXACTLY the same volume each time, it's only an approximation.

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It's really just a matter of simple math. It shouldn't matter how much you boil off, but more KNOWING how much you've boiled off. I have a metered stick so that I can tell what my kettle volume is at any time. If you know your gravity at 6 gallons, it's easy enough to calculate it for 5 gallons, or 5.2 gallons, or 4.9 gallons. Sure, I'm relying on math instead of measuring it directly. However, every time I have done both a pre-boil and post-boil reading, the numbers have worked out to within one gravity point. Don't get me wrong, I'm not saying that everyone should stop taking post-boil readings. It's just that it seems to be redundant the way that I brew and knowing my system.

I take both as I want to know in advance if I need to add DME to my all-grain wort if I really messed up bad, and I take it after as I don't know if the pre-boil is a good reading since you can get separation. That said, my pre-boil is now taken from the same jar I collect my irish moss wort which is just after the boil starts and before I add the bittering hops, so it's really "first boil" reading, not "pre boil".

whatsleftofyou said:

It's really just a matter of simple math. It shouldn't matter how much you boil off, but more KNOWING how much you've boiled off. I have a metered stick so that I can tell what my kettle volume is at any time. If you know your gravity at 6 gallons, it's easy enough to calculate it for 5 gallons, or 5.2 gallons, or 4.9 gallons. Sure, I'm relying on math instead of measuring it directly. However, every time I have done both a pre-boil and post-boil reading, the numbers have worked out to within one gravity point. Don't get me wrong, I'm not saying that everyone should stop taking post-boil readings. It's just that it seems to be redundant the way that I brew and knowing my system.

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Of course, this is correct, but everything depends on the accuracy of your volume measurements. I doubt that a metered stick is accurate to 0.1 gallons, but in the end I don't thing we're talking about much more than a gravity point or three.

L

I only take a post-boil measurement. If I miss my OG, it is almost always a bit on the high side.

jldc said:

Of course, this is correct, but everything depends on the accuracy of your volume measurements. I doubt that a metered stick is accurate to 0.1 gallons, but in the end I don't thing we're talking about much more than a gravity point or three.

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I'm sure it isn't quite that accurate, no. I have it marked in 1/2g increments and estimate from there. Ultimately yes, not more than a point or three difference. I understand wanting to know, but for me a point or three isn't going to change the beer perceivably.

Perhaps it's as Yooper said at the beginning, "Maybe it's just a yooper thing". That being the case, I'll take a beer and a pasty!

Why throw away the post boil gravity reading?

I save mine and put them into canning jars and boil them quickly. Save it for Spiese, Starters, etc.

Tinga said:

the sugars don't evaporate but the water does. i would think this would make it heavier because there is less water for the sugar to be in so wouldnt it be more concentrated and more heavy?

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whatsleftofyou said:

The gravity reading will be different, you're right. My point was that if you know your pre-boil gravity, then you can easily calculate your post-boil gravity without having to directly measure it.

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Mateo said:

Why throw away the post boil gravity reading?

I save mine and put them into canning jars and boil them quickly. Save it for Spiese, Starters, etc.

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My system is pretty much nailed down- I start with 7 gallons exactly and end up with 5.25 gallons exactly. When I did take preboil and post boil refractometer readings, they definitely were the same (corrected for boil-off). The sugars are in the wort- water evaporates, but sugars don't. If they don't correspond, then there is a problem. I don't bother most of the time any more for post-boil readings unless I suspect an issue, like more or less boil-off than expected, or more trub losses than usual.

I use a refractometer, about two drops of wort. It's not that I don't want to lose wort, it's just that I don't really see the point of a post-boil reading if I've done a preboil reading. When my system was new, I always did both readings. I'm very comfortable with my system now, and it never varies.

@ Tinga - Yes, I realized after I hit 'post' that someone would point out that gravity changes with evaporation. I had forgotten to say that one thing that is spot-on consistent is my evaporation rate, so I can easily do the math to get my O.G., even without measuring.

You know - one problem that I have is that I normally ferment in a 6.5 gallon glass carboy. After I add top-up water, it's not always so easy to get a sample for a hydrometer reading (considering I keep breaking the racking cane on my autosiphons and therefore won't buy any more). At that point, I'm usually tired (and so is SWMBO).

If I'm using a hydrometer for the pre-boil measurement, could I pour the wort back into the pot since the boil should sanitize the re-introduced wort?

ArcaneXor said:

I don't usually take any gravity readings any more, unless I am making an "unusual" beer for my setup.

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That's kind of silly. Why?

YooperBrew said:

When I did take preboil and post boil refractometer readings, they definitely were the same (corrected for boil-off).

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Are you using software to calculate the boil-off correction? Is there a basic formula to make the conversion fairly quickly?

I'm new to all grain, which is probably why I take both, but I pull the preboil sample and stick it in the freezer to cool it down to a temp I can take a gravity reading at, take the reading, and then throw it back into the boiling pot, which has usually just started boiling by the time my sample cools down. This way I'm only wasting 1 sample

dummkauf said:

I pull the preboil sample and stick it in the freezer to cool it down to a temp I can take a gravity reading at

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Even easier yet, BeerSmith (and probably some other software too) has temp correction for your hydrometer built in. Take the reading, take the temp, calculate, done.

Haputanlas said:

Are you using software to calculate the boil-off correction? Is there a basic formula to make the conversion fairly quickly?

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To answer my own question, here is a link to a site that will do the calculation:

http://onebeer.net/boilcalc.shtml

whatsleftofyou said:

Even easier yet, BeerSmith (and probably some other software too) has temp correction for your hydrometer built in. Take the reading, take the temp, calculate, done.

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It's still more accurate to cool and measure. Gravity reading taken at high temps are notoriously inaccurate even after correcting for temp.

joety said:

It's still more accurate to cool and measure. Gravity reading taken at high temps are notoriously inaccurate even after correcting for temp.

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That is true. That's one reason I love the refractometer for preboil gravity. Use the pipette, let it sit for a minute, then put two drops on the lens and read! With a hydrometer, any reading taken over about 100 degrees is pretty inaccurate even with the temperature correction chart. I would cool the sample down to under 100, take the reading, and then consult the correction chart. That's pretty accurate.

It's all about being comfortable with your system. What works for me probably won't work for others. A few years ago, I did things a bit differently. Not better, not worse, just differently. I'm much more relaxed in my process, and my beer is pretty good so I'm happy.

YooperBrew said:

That is true. That's one reason I love the refractometer for preboil gravity. Use the pipette, let it sit for a minute, then put two drops on the lens and read! With a hydrometer, any reading taken over about 100 degrees is pretty inaccurate even with the temperature correction chart. I would cool the sample down to under 100, take the reading, and then consult the correction chart. That's pretty accurate.

It's all about being comfortable with your system. What works for me probably won't work for others. A few years ago, I did things a bit differently. Not better, not worse, just differently. I'm much more relaxed in my process, and my beer is pretty good so I'm happy.

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Plus, I use a hydrometer with a built in thermometer, which only goes up to 120F, so I need to cool it before I can get a temp reading either way.

And I have personally witnessed a BeerSmith corrected measurement having a 5 point difference between the same sample at 110F and 60F.

I take preboil readings with my refractometer, and I almost always take a post-boil hydrometer sample to taste.

Interesting. I never would have guessed that the temp correction would be that far off. It seems logical that it'd just be a matter of a relatively simple formula. That's why I love this forum, learn something new all of the time.

Haputanlas said:

That's kind of silly. Why?

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Familiarity and laziness, to be honest. I should probably get back to taking those measurements more frequently, just in case.