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Hi all,

A simple but potentially important question.... If there are bubbles in the testing tube when you are measuring the SG, does this affect the reading? For instance, when measuring the SG towards the end of a ferment.

I think it does a bit, at least by a few points. I've started putting a cap on both ends and shaking for a while, let settle and repeat a few times.

Other people's thoughts?

Cheers,

Adam L

It does affect the reading if you get bubbles on the surface of the hydrometer. The technique for dislodging the bubbles is to spin the hydrometer.

Brent/Bret: Glad you post disappeared.

RWH: Cheers. I use the spin method but quite often get air bubbles attaching to the hydrometer as it settles. I find it makes a 2-3 point difference compared to flattening the beer first. It also gives a level playing field when comparing reading day to day. This helps me to decide when to rack.

Granted thought, it's probably not the most important thing I've asked about. Sorry if this is beneath this forum.

Cheers,

Adam L

alangman wrote:... Granted thought, it's probably not the most important thing I've asked about. Sorry if this is beneath this forum.
...

Alan, No question should be regarded as below the forum*. It is quite an important question actually - for all the comments about SG, OG, FG and IG's etc. very little discussion is given over to hydrometer technique/usage.

Cheers,
Greg

* Please however have a quick search to see if your answer is in the forum already. Also try to keep it at least somehow related to beer.

Hey AlangMan ^_^,
do yourself a favour and get a proper test tube thingy as well.
the hydrometer seems to stick to the sides of the stupid case that they come with.
and spin spin .n times

cheers
501

501 wrote:Hey AlangMan ^_^,
do yourself a favour and get a proper test tube thingy as well.
the hydrometer seems to stick to the sides of the stupid case that they come with.
and spin spin .n times

cheers
501

Yeah, theres a reason that monash charges me $20 a sem breakages fee for chem, got a good thermometre that way.

I pour my sample from cup to cup a few times to degas the stuff before putting it into the test tube,it makes a lot of difference to the final reading.

I let my test tube sample rest until bubbling stops. Usually half an hour or so.

Suspect I then get a more accurate reading.

I walked Nowra end to end yesterday looking for a 240x25 test tube, rose vase, spaghetti tube, drill case .. whatever, but preferably glass and came up with zilch.

I've got 2 hydros, thin with a case and fat without and would just like a good glass skinny test jar/tube. Any pointers appreciated.

Cheers, Geoff.

Hi Geoff,

As with most HBrs, have broken a hydro or two. And yes, acquired a short fat hydro from Big W. Comes with no test tube. Sawed one of my long plastic test tubes in half, and it now accommodates my short fat hydro nicely.

Much easier to read the short hydro for FG readings, if the one you are talking about is the same as mine.

Hope this helps.

I bought a 250ml graduated measuring cylinder from these guys a while ago. Not sure that you need to go so hgh tech for a hydrometer test tube but I'm sure these guys would have something.

http://www.testtube.com.au/

Most HBSes I've been to have jars specifically designed for this. They're just a piece of transparent PVC pipe, inserted into a red plastic base. $7 I think. You could probably make your own with a bit of silicon sealant or something.

Hi all,

Thanks for the replies. I did a test last night. I'm making a wash at the moment and I measured the SG by filling the tube from the spigot and spinning the hydro. The reading was 1050. Then, I removed the hydro, capped the tube and shook it, then removed the cap to let out the gas. I repeated this for ~2 mins and then left the sample for 15 mins (cap off). The SG after this was ..... 1032! That's almost 20 points different .

So, after this experiment, I'm definitely going to de-gas my samples before measuring the SG.

Cheers,

Adam L

mark68 wrote:I pour my sample from cup to cup a few times to degas the stuff before putting it into the test tube,it makes a lot of difference to the final reading.

Nice hint buddy!

you are the man. I will do that from now on.

alangman wrote:I measured the SG by filling the tube from the spigot and spinning the hydro. The reading was 1050. Then, I removed the hydro, capped the tube and shook it, then removed the cap to let out the gas. I repeated this for ~2 mins and then left the sample for 15 mins (cap off). The SG after this was ..... 1032! That's almost 20 points different .

So, after this experiment, I'm definitely going to de-gas my samples before measuring the SG.

Cheers,

Adam L

Just noticed that your testing the SG? is this a mistake? SG meaning Starting Gravity? or Sp.G Specific Gravity? I've never had bubbles in my starting wort so I assume you mean FG Final Gravity. There's also IG Initial Gravity and OG Original Gravity is another one. Bloody confusing eh.

I just let the sample sit a while and then give the hydrometer a spin to make sure. I've never had nearly 20 points difference, but this is a good way to show the importance of good use of a hydrometer.

IG is also Intermediate Gravity - the SG on day x when it has come off high krauzen.

Cheers,
Greg

Maybe we should have some standardised abbreviations. I must admit sometimes I look at something like LCPA and wonder what type of pale ale are we talking about.

Hi all,

Sorry for the confusion, I was using SG to mean Specific Gravity.

Cheers,

Adam L