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SG Confusion

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UKTony

UKTony

Worker Bee
Registered Member
Dec 24, 2012
270
1
18
Richmond, VA
I just took a SG reading from my brew today (24 hours after pitching) and the readings I got were significantly less alcoholic than the day before, I assumed that the honey had separated out some and I'd gotten a thief full of honey rather than a good mix. I whisked it up and got a result more in line with what it should've been.

I've never seen it written that you should mix before you take a sample... so I guess my question is:

Is this normal and is it advised to mix/stir before sampling during fermentation??

Cheers

Tony.
 
UKTony said:
I just took a SG reading from my brew today (24 hours after pitching) and the readings I got were significantly less alcoholic than the day before, I assumed that the honey had separated out some and I'd gotten a thief full of honey rather than a good mix. I whisked it up and got a result more in line with what it should've been.

I've never seen it written that you should mix before you take a sample... so I guess my question is:

Is this normal and is it advised to mix/stir before sampling during fermentation??

Cheers

Tony.
Click to expand...
Sounds to me like you're using one of those piss poor multi-scale hydrometers Tony ?

You mention "less alcohol" which suggests, to me, that you had something like yesterdays reading say e.g. 14% and todays says 11% ?

Or something like that ?
 
*note to self......Don't hit the send button when trying to scroll with thumb;)

Anyway....... so the scale that's easiest to read/follow is the standard gravity scale. It'll be marked from either 0.980/0.990 at the top probably down to something like 1.150 possibly a bit higher.

If your SG yesterday was e.g. 1.120 and today its 1.110 then it would tell you that its loss or drop is 10 points yes ?

Yet if you lined up the numbers with the % alcohol markings, yesterday it would have been on the 16% mark (again just example numbers) and today its telling you that its only 15 or maybe 14%. So its not telling you how much alcohol has been made its telling you how much more it can make.

As I say.....piss poor and counter-intuitive.

Your only way of knowing exactly (well as close as dammit) the strength of a batch is to know how many gravity points its dropped from start to finish and convert that to % ABV and even then its not perfect because if you back sweeten at the end it'll drop a bit or if you fortified it with whiskey or brandy etc it's gonna increase......

As long as the numbers are going down, it's heading in the right direction...
 
My OG was 1.104 24 hours ago.

I took a sample today, and the first sample was 1.140 and fizzing. After realising something was messed up, I took the drill to the bucket and beat the living crap out of the must, then took another sample which showed 1.100, much more inline with what I was seeing in the airlock (although I thought I'd have eaten up more of the honey than that).

You can see the actual photo of the reading in the patrons brewlogs.

I only have a triple scale... I'm not sure what else to use, recommendations are welcome, I was going to get a refractometer to use, but was told that I need something that measures Gravity.

Cheers

Tony
 
Ah, 2 fold problem then ;) too many scales on hydrometer and a sh1tload of CO2 raising the damn thing......

Seems that while they do sell multi-scale hydrometers here too they're more frequently single scale......bigger print/easier to read etc.....

The colour bands suggest it might be a multiscale one.....not seen coloured bits printed on single scale models.....

Refractometer is designed to tell you the sugar content but you have to modify or allow for error of the reading once there is alcohol present.

Often used to check the sugar level of grapes prior to harvest and also available with different scales just to add confusion.....hydrometer generally thought to be easiest.
 
Bit hard too see how nice and readable the scale is on a smartphone. Looks tidy though, especially if it gives you the gravity deviation by temp instead of having to apply +/- numbers after taking a reading then measuring temp..... something that I singularly fail to do.....

I just measure gravity with the "that's close enough" presumption :)
 
UKTony said:
I just purchased this....

http://www.midwestsupplies.com/pro-model-precision-thermohydrometer-by-alla.html

Overkill? Perhaps.... but I'm hoping it'll be clear and accurate. And not really that expensive when you compare it to something like photography as a hobby!!

It should be here in a couple of days
Click to expand...

VERY nice piece of equipment. Brewing is like golf, cars or audio; you just can't have enough gadgets. Mine is one of those counter-intuitive ones... percent on one side and gravity on the other... I always found it really easy to read however. The first reading is how much potential alcohol you can make and the last reading is how close you got.

Potential 17% at start minus potential 3% at the end means I have 14% alcohol in my finished product and 3% of the sugar is left to sweeten the taste. Of course, I also always "forget" to take a temp reading at the start so the real starting figure is probably always off by a little.
 
To answer your original question, stirring may well be called for, but not in order to re-mix the honey. I've never heard of honey dropping to the bottom after it's already been stirred in adequately. The main problem was most likely that the CO2 in solution formed bubbles on the hydrometer, giving it some added buoyancy and thereby giving you a falsely high reading. Stirring would get rid of a lot of those bubbles. One way to check if bubbles are your problem is to give the hydrometer a quick spin and see if the reading changes. If it changes then you had bubbles. If not, you probably didn't.
 
kuri said:
To answer your original question, stirring may well be called for, but not in order to re-mix the honey. I've never heard of honey dropping to the bottom after it's already been stirred in adequately. The main problem was most likely that the CO2 in solution formed bubbles on the hydrometer, giving it some added buoyancy and thereby giving you a falsely high reading. Stirring would get rid of a lot of those bubbles. One way to check if bubbles are your problem is to give the hydrometer a quick spin and see if the reading changes. If it changes then you had bubbles. If not, you probably didn't.
Click to expand...

Almost 100% certain I had bubbles... the sample I had looked carbonated and I guess in every sense of the term it really was!

The stir I did before the next sample gave me about 6 inches of foam!!
 
It arrived today, but I didn't have time to set it up before I took my readings tonight, but I'll post some pics later but the thing is huge and comes with its own tube (bucket), so if I do use this I'll have to pour it all back or I'll end up going through 3 gals before the damn thing is done!

I think it's really intended for the likes of Oskaar and Medsen, who brew in 10's of gallons rather than 5 or 6. I can't get over how big this thing is!

Sent from my iPad using Tapatalk HD
 
As promised a photo of the behemoth.

This is a 16oz Snapple bottle next to the Thermohydrometer.

6Q83HvN.jpg
 
Ok, just measured side by side, fancy certified calibrated thermohydrometer, vs $3 multi scale thingamajig. Looks to me like fat bloke called it right.

Yesterday my must measured 1.080 SG (cheap one)

Tonight cheap one measured 1.070 (not unexpected)
Fancy one measured 1.080.

So if we assume that the big fancy one is right then the cheapo is out by about .010, so I'll continue to measure them side by side for this batch. On the plus side, while the must is in the bucket, I can take readings directly from the must, won't be able to do that once its been racked tho.

So whilst at this stage .010 isn't a lot, I'm guessing if the margin of error remains the same all the way, .010 error at 1.000 is more significant.

Anyway there you have it.

Tony
 
UKTony said:
So if we assume that the big fancy one is right then the cheapo is out by about .010, so I'll continue to measure them side by side for this batch.
Click to expand...

There is a way to test this. Get some water at 60F or 68F (depends on the hydrometer, some are calibrated for one or the other temperatures in my experience) and and see where they are at. They both should read 1.000 or if you want to get really anal about it, use distilled water at that temperature. Then you can see how each is calibrated and determine which one is more correct and can adjust as need be.

-- Steve
 
Well that was the end of that fancy thermo-hydrometer, aka $50 down the proverbial kahzee.

I didn't knock it or drop it or anything, I was simply holding it by the stem, and the tip seems to have sheared off, very cleanly at the end, no shattering or fragmenting.

For the .002 - .006 variance across the range when compared to the expensive calibrated ones, I'll stick to the cheapo's in future!
 
Kudos to Midwest Supplies yet again, who agreed that this looks like a manufacturing flaw and have agreed to send another one out. I'll have my fancy thermo-hydrometer back again soon!

Tony
 
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