Using Hydrometers

[JindStar]

Heya every1, am a new brewer up to my 3rd brew (which went explodey on me overnight, foamed through the bubbler and looks like it might do it again!) I've been searching for clearer instruction on how to use a hydrometer, which a lot of my friends don't use. I think one of my difficulties is I have a long flask and a short hydrometer, but if someone could explain the Idiots Guide to Hydrometers for me that'd be awesome!

 

[manticle]

Fill vessel almost to top
Bulbous end of hydrometer goes into liquid first
Spin hydrometer (helps remove bouyancy resulting from Co2 bubbles)
Allow to settle slightly.
Read numbers where liquid line meets hydrometer. If it changes slightly, take the lowest reading.

Larger vessel with smaller hydrometer is better than large hydrometer in small vessel.
Calibrate your hydrometer by ensuring that it reads approx 1.000 in 20 degree water.

 

[Pennywise]

Welcome to the forums :icon_cheers:

It doesn't matter what type of tube/hydrometer you have so long as the hydrometer doesn't touch the bottom of the flask. What you should be doing is dropping the hydrometer into the test flask, giving it a bit of a spin to get rid of any bubbles attatched to it, hold it up at eye level and you'll notice around the hydrometer the wort/beer looks like it's trying to climb up it. The correct reading is the highest point where the beer is (so not actually the level of the rest of the sample). Hope that makes sense, I get the feeling I haven't explained it too well :unsure:

Edit: beaten

 

[muckey]

just to add to previous posts

the liquid surface is called the meniscus - you read the level at the high part of the meniscus where it touches the hydrometer

always try and minimuse the amount of froth on top of your sample

 

[JindStar]

Thanks for that I just noticed that all the water has been pushed out of my bubbler( I've not long cleaned up the foam and resantised and refilled it), should I add more sterile water or just put a bit of clingwrap and rubber band on top?

 

[muckey]

either, I used to just top up with a bit more cooled boiled water but glad wrap works equally weel

matter of fact I just put a shot glass over the airlock hole these days

 

[HarryB]

the liquid surface is called the meniscus - you read the level at the high part of the meniscus where it touches the hydrometer

Sorry, but this is wrong as far as I'm concerned. You should be reading level with the plane of water, not where the meniscus comes up around the hydrometer. This is the same with measuring cylinders and any similar applications.

 

[Pennywise]

If you have such a good ferment maybe grab some tubing and stick that where the airlock goes, put the othe end in a jar filled with no-rinse sanitiser. it doesn't sound like she's going to calm down for a bit.

 

[Scruffy]

I can't work it out either... sometimes it reads 1008, sometimes 1060, sometimes less occasionally more...

A hydrometer is an instrument used to measure the specific gravity (or relative density) of liquids; that is, the ratio of the density of the liquid to the density of water. It's not just sugar...

Some hydrometers come inside a plastic tube - you don't want to pour too much away when checking, nor do you want to repeatedly plunge the instrument into your fermenter (unless you sterilise and leave it in there, like i've done occasionally!!)...

Nothing like pictures, eh...

And a link to click on... (where I got the first pic from...)

Edited to add - the second picture shows a hydrometer with a scale you might not be familiar with - Brix - it's just another way of showing the percentage of stuff in liquids (fermentable and non fermentable - it's why your brew might finish between 1005 - 1015 Specific Gravity, or 1.28brix to 3.82brix, not 1.000 - 0.00brix - the reading for potable tap water at room temp). You read it the same way.There's other scales too:

Baum scale, formerly used in industrial chemistry and pharmacology
Brix scale, primarily used in fruit juice, wine making and the sugar industry
Oechsle scale, used for measuring the density of grape must
Plato scale, primarily used in brewing and probably your scale...
and the Twaddell scale, formerly used in the bleaching and dyeing industries

Also hydrometer readings alter depending on the temperature of the liquid - not by a huge amount [URL="http://"http://hbd.org/cgi-bin/recipator/recipator/hydrometer.html?11585439""]but near it in mind...[/URL]

 

[muckey]

Sorry, but this is wrong as far as I'm concerned. You should be reading level with the plane of water, not where the meniscus comes up around the hydrometer. This is the same with measuring cylinders and any similar applications.

you are correct when measuring volume - alway take as the level part (at the bottom for water but not all liquids)

in the case of the hydrometer you are measuring density not volumes and they are calibrated to be read a certain way. The 1 I have definately says read at the top of the meniscus

 

[HarryB]

you are correct when measuring volume - alway take as the level part (at the bottom for water but not all liquids)

in the case of the hydrometer you are measuring density not volumes and they are calibrated to be read a certain way. The 1 I have definately says read at the top of the meniscus

I think your hydrometer would be in the minority then, but it's handy to know such beasts exist.

The best way to tell is to get some 20deg water and see where the 1.000 line comes up to... this should be where you take all your measurements.

 

[katzke]

All of you have it wrong.

You do not buy them to use them, you buy them to break them.

At least that is the common consensus in all the hydrometer threads that I have read.