Makeshift Hydrometer

[kathomas]

Ok so my hydrometer broke during brew day before I could actually use it (it was incredibly fragile and just snapped as I was lifting it). I read up some on it, and decided that I would try to use a scale instead (measuring equivalent volumes of water and beer to get the specific gravity). Unfortunately, I had to order a scale, so I never got my OG reading. I was planning to just take the gravity for a few days and if its stable, just continue to bottling (it's been in primary for 2.5 weeks already). It's not ideal, but should work, right?

Out of curiosity, does anyone know what OG/FG for Brewer's Best Milk Stout usually is so I have at least some sort of comparison? I'll post the first FG reading later tonight I imagine.

Cheers,
Katie

 

[1Mainebrew]

I'm sorry to burst your bubble, but go and return the scale and buy another hydrometer. Depending on how much you paid for the scale, go and invest in a refractometer. Its WAY easier.

 

[Shizog4]

How much was the scale? My hydrometer was $8.99 almost seems silly to by something else

 

[amandabab]

It's not ideal, but should work, right?

nope, never.

 

[kathomas]

Explain to me why this won't work. The specific gravity is just the ratio of the mass of the beer to the mass of water...I just filled the wort up to 40mL on the graduated cylinder and measured the mass. The mass of 40mL of water is obviously 40g, so just divide the masses and I got an SG of 1.0204.

The scale was about 12 bucks and measures to +/- 0.1g, and it has the added benefit of being useful for other things as well.

 

[Draken]

Explain to me why this won't work. The specific gravity is just the ratio of the mass of the beer to the mass of water...I just filled the wort up to 40mL on the graduated cylinder and measured the mass. The mass of 40mL of water is obviously 40g, so just divide the masses and I got an SG of 1.0204.

The scale was about 12 bucks and measures to +/- 0.1g, and it has the added benefit of being useful for other things as well.

Specific gravity is a measure of density not mass.... You might be able to calculate it using weight, temp and volume, but I am quite sure it's more complex a formula than what you are doing.

 

[kathomas]

It's the same volume I used for beer and water, so it ends up canceling out of the equation since density is just mass/volume.

Working with density it would be
[(mass of beer)/(volume of beer sample)]/[(mass of water)/(volume of water sample)].
The scale gave me the mass of beer, the graduate cylinder showed the volume of the beer, and basic knowledge of the universe tells me that for water 1mL is 1g so I know the mass and volume of the water as well. It's simple division.

 

[amandabab]

.1gram accuracy isn't anywhere near accurate enough without a huge sample even if density and particulate count were a strait line conversion to mass.

 

[airving]

I believe the math is good. I calculate about .002 error based on the +/- .1 gram in the 40 ml sample size. If we also allow an error reading the volume of about 0.25 ml ( granted, I'm not sure if this is reasonable), you could be off more than .005 ( additional ).

That error scales inversely to the sample volume, and we shouldn't see an increased error size for a larger sample (still .25 ml off, for example). An 80ml sample cuts those errors in half, and that's getting into a range that I'd be happy with.

Having said that, order the hydrometer now. You're not accounting for floaties like hop particles, break material, yeast, or gas bubbles that will affect volume and weight. I'm not sure how big an effect those would have, but you'd probably need to filter and de-gas your sample prior to weighing for best accuracy.

 

[kathomas]

You're not accounting for floaties like hop particles, break material, yeast, or gas bubbles that will affect volume and weight. I'm not sure how big an effect those would have, but you'd probably need to filter and de-gas your sample prior to weighing for best accuracy.

First off, thanks for the detailed response, airving. I'm a little confused though, when you say I'm not accounting for things in the beer (particles and whatnot) what do you mean? A lot of people take samples of the beer and put the hydrometer in the sample rather than the whole fermenter. How would using the hydrometer versus the scale in this situation take into account those things?
-Katie

 

[jvp1]

Your calculations are based on the mass of the beer, and the mass of the beer will be affected by such things as yeast or grain particles. Ie, your SG will end up being higher or lower if you have a bunch of grains floating in your sample. A hydrometer eliminates this.

I think the scale-method is a great idea in a pinch, but I would recommend getting a new hydrometer. I have a kitchen scale so if my hydrometer ever breaks, I'll probably use it if I need to, by the way...

 

[Draken]

It's the same volume I used for beer and water, so it ends up canceling out of the equation since density is just mass/volume.

Working with density it would be
[(mass of beer)/(volume of beer sample)]/[(mass of water)/(volume of water sample)].
The scale gave me the mass of beer, the graduate cylinder showed the volume of the beer, and basic knowledge of the universe tells me that for water 1mL is 1g so I know the mass and volume of the water as well. It's simple division.

But what is the weight of 1mL of water at the same temp as your wort?

 

[kathomas]

But what is the weight of 1mL of water at the same temp as your wort?

The mass of 1mL of water is 1g at room temperature by definition (it changes slowly enough with respect to temperature that a 20 degree swing in either direction is only about 0.001% off from 1g). The weight is just (mass)*(acceleration due to gravity) so (mass of sample)*(9.8m/s^2). However, weight isn't necessary in this calculation, only mass and volume (because gravitational acceleration is obviously constant for everything on the earth's surface).

 

[bernerbrau]

Specific gravity is a measure of density not mass.... You might be able to calculate it using weight, temp and volume, but I am quite sure it's more complex a formula than what you are doing.

Density is mass divided by volume. How is that complex?

That said, I doubt the precision will be that great. Serviceable, but not great.

 

[kathomas]

Yeah, I think I'll probably get a hydrometer eventually, just need to find one that isn't so fragile.

 

[mappler]

Katie,
The OG is 1.057-1.061. The FG is 1.020-1.024. I can also report it currently tastes very good at 39 degrees with 2.15 volumes of CO2 being pushed with a Nitrogen/CO2 blend at 30PSI through a stout faucet...

Also, the Austin Homebrew clone of the Left Hand Milk Stout might taste even better once it carbs up...

-Matt

 

[bernerbrau]

Yeah, I think I'll probably get a hydrometer eventually, just need to find one that isn't so fragile.

I'd spring for a refractometer if you can afford one.

 

[1Mainebrew]

i'd spring for a refractometer if you can afford one.

+1

 

[supermoth]

I'd spring for a refractometer if you can afford one.

Doesn't the refractometer get a little complicated when it comes to final gravity?

Don't send back the scale! You can use it for measuring hops, priming sugar, or anything else in your kitchen.

 

[ACbrewer]

40g *1.0204=40.816g How did you get such an acruate read on a scale that is acurate to .1g?

In theory the idea works, but the error bars are larger than desirable. I think you'd have to measure out closer to 500g (about a pint) to get close enough.

 

[passedpawn]

Scale probably won't work without a bunch of effort. Hydrometer measures densities of DISSOLVED SOLUBLE SUGARS. Things in the wort that aren't soluble, like the fat lipids, hop proteins, and yeast sitting on the bottom of the hydrometer jar won't contribute to the reading. But those things will negatively affect a scale measurement unless you are careful to exclude them.

If you could exclude everything but the solution, and you could measure volumes accurately, it could work.

 

[ScottSingleton]

It's Anything soluble, fermentable sugars or otherwise. Salt, and other solubles also affect the specific gravity. Solids and non-solubles.just flow out of the way

 

[1Mainebrew]

Doesn't the refractometer get a little complicated when it comes to final gravity? QUOTE]

No way, refractometers are unbelievably easy to use. You get a drop of beer, put it into the sight glass, turn it on, and there you have it. If you want to, you can get a conversion from brix to SG using any online conversion program. Its sooooooo easy.

 

[ScottSingleton]

As long as you know your starting gravity you can always determine you current/final gravity.