Water volume by weight

[shredthrash]

Hi all,

In order to get around the slight variations in water volume based on temperature and also to stop trying to measure my brewing water with pails, sight glasses, volume markers, etc, I decided to start measuring my water volume by weight.

Ex. I'm assuming that the weight of 1L of water is always 1 KG, so if I need 20L of strike water I will weigh out 20 KG of water.

Furthermore, when I am done collecting my wort out of the kettle I will weigh the carboy (having already accounted for the weight of the empty vessel) and then divide that value by my SG to get an accurate representation of the volume in the fermentor.

I was just wondering if there are any areas where people can tell me that I'm wrong, that I'm missing something, or just general criticism or tips.

Thanks very much and I hope that I posted this in the right area!

- Ben

 

[kh54s10]

Just seems like way more trouble than it is worth. My variation in wort going into the fermenter usually varies only a quart or so.....

 

[hezagenius]

Sounds like a plan to me. I use weight for my processes since I ferment in a closed vessel.

 

[shredthrash]

Just seems like way more trouble than it is worth. My variation in wort going into the fermenter usually varies only a quart or so.....

It's actually way less effort for me. I put a pail on a scale and turn on my RO tap until it reads strike volume. When I'm cooling in my wort, my carboy simply goes onto a scale instead of the ground. Super convenient with more accuracy in mind.

 

[Oginme]

I've been weighing my water volume for several years now. Much more accurate and I am never off my more than 20 ml out of a 28 liter batch. For those using Imperial of US volume measurements, that is less than an ounce in 7.4 gal. You need to remember that this is water at standard conditions and account for thermal expansion at strike temperature.

 

[kh54s10]

It's actually way less effort for me. I put a pail on a scale and turn on my RO tap until it reads strike volume. When I'm cooling in my wort, my carboy simply goes onto a scale instead of the ground. Super convenient with more accuracy in mind.

I don't see less effort. I fill my HLT, heat, drain of my strike amount. drain mash tun and measure with a dip stick. sparge to boil off volume. boil. drain to fermenter - no weighing anything. If anything it is the same.... How accurate do you need to be. IMO, not much.

 

[shredthrash]

I don't see less effort. I fill my HLT, heat, drain of my strike amount. drain mash tun and measure with a dip stick. sparge to boil off volume. boil. drain to fermenter - no weighing anything. If anything it is the same.... How accurate do you need to be. IMO, not much.

I appreciate your reply and I'm not questioning your approach to home brewing. I was however posting a question for people to analyze my process and tell me where I have gone wrong, not weather my brewing technique was right or wrong or less or more effort than another way.

Thanks for commenting, but if you not only do not use this technique, but are opposed to it, I'm not sure what specific help you can offer!

 

[Vale71]

Ex. I'm assuming that the weight of 1L of water is always 1 KG

This is clearly not the case as the density of water changes with temperature, which is what you're having issues with by your own admission. Water density equals 1.000 at exactly 4.0°C. At 20°C, which is the temperatures that is considered standard, density is only 0.9982 so in your case to get 20 liters at 20°C you'd have to weigh out 19.964 kilograms.

 

[shredthrash]

Hey!

Thanks for commenting! What you've stated is what I am aware of and trying to get around with weighing my strike water; density changes relative to temperature and/or pressure, but mass does not. The weight of 1L of water is 1KG at both temperatures you've listed. The density math that I stated at the tail of my post already corrects for temperature when I adjust my hydrometer sample based on my cool-in temperature.

 

[shredthrash]

Sorry: the relative mass of that same 1L of water will be the same for that sample if you ramp the temp up or down.

 

[Soulshine2]

seems like a lot of effort, too much weighing . I do pretty much what kh54s10 does. I have kettle#1 only for strike/sparge water I fill to capacity which is 7 gallons. I keep another 1 gallon in a jug at room temp for small temp adjustments while in the mash tun. I heat pot #1 to 15 degrees above my high end of mash temp, dump a little in the (igloo cooler)tun to preheat and monitor the temp. When it comes down to low end of mash temp I add enough more heated water to bring it back to 15 degrees above mash and add my grist, stir and add more water (from either kettle or jug ) to my mash temp and volume,let it mash for the time needed . If its a single mash infusion , I just monitor the 60 minutes . If its a step mash I'll keep adding heated water until I reach those temps for whatever time frame necessary, and then drain/sparge to the kettle#2 until I hit my preboil volume which is 6.5 or 7 depending on my available carboy (5 or 6g) and target gravity. After that its just a typical boil for time (hops, and other additions) and volume. I have yet to be disappointed on the target gravity with this method. I take a pre-boil gravity . I know my boil off and I could almost at this point eliminate doing a post boil gravity reading because up to now,its been what was intended give or take 0.001 .

 

[Vale71]

Hey!

Thanks for commenting! What you've stated is what I am aware of and trying to get around with weighing my strike water; density changes relative to temperature and/or pressure, but mass does not. The weight of 1L of water is 1KG at both temperatures you've listed. The density math that I stated at the tail of my post already corrects for temperature when I adjust my hydrometer sample based on my cool-in temperature.

Let me try again. The weight of 1 kilogram mass is always 1 kilogram on the earth's surface. You should actually also correct for altitude but since you're unlikely to brew on the Himalaya (and even there the difference in earth's gravitational pull is microscopic) we can forget about that. The weight of 1 liter of water changes with temperature. If your calculations (either performed by hand or with some software) ask for 20 liters of water, those will be 20 liters at 20°C (standard temperature). If you want to translate that into a weight measurement you have to consider the density at 20°C and multiply that by the required volume to get your target weight. From that point on since you're working with weight only you can ignore the actual temperature water has at the time of measurement, which could very well lie anywhere between 0°C and 100°C.
Of course the differences are very small but it's important that the principle is understood in order to avoid any pitfalls in future calculations.

 

[kh54s10]

Sorry that I cannot help with the calculations, I just don't see the value. Why do you need to be so accurate? Seems like a solution looking for a problem to me.

 

[schematix]

I think this is the way (get it?) to go if its easy for you.

For me it's difficult because it usually takes me about 16.5-17G of strike water. Not only is that a lot of volume, but it weighs a lot too. Less lifting is better for me.

I did a weight calibrated check (weighed water on a scale) against my sight glass markings once and it was reasonably close. Since these days i tend to repeat/tweak recipes more than I used to, i make really good notes about volume and gravity at various points and that helps to dial it in too.

 

[LittleRiver]

In order to get around the slight variations in water volume based on temperature and also to stop trying to measure my brewing water with pails, sight glasses, volume markers, etc, I decided to start measuring my water volume by weight...

How are you proposing to measure your volume during the boil, so you can see if you need to stop the boil or continue it to reach the target?

 

[Vale71]

How are you proposing to measure your volume during the boil, so you can see if you need to stop the boil or continue it to reach the target?

Easily solvable by measuring gravity. From a gravity measurement it's trivial to calculate actual boil-off and from that and the starting volume the current volume can be easily calculated.

 

[shredthrash]

Let me try again. The weight of 1 kilogram mass is always 1 kilogram on the earth's surface. You should actually also correct for altitude but since you're unlikely to brew on the Himalaya (and even there the difference in earth's gravitational pull is microscopic) we can forget about that. The weight of 1 liter of water changes with temperature. If your calculations (either performed by hand or with some software) ask for 20 liters of water, those will be 20 liters at 20°C (standard temperature). If you want to translate that into a weight measurement you have to consider the density at 20°C and multiply that by the required volume to get your target weight. From that point on since you're working with weight only you can ignore the actual temperature water has at the time of measurement, which could very well lie anywhere between 0°C and 100°C.
Of course the differences are very small but it's important that the principle is understood in order to avoid any pitfalls in future calculations.

Exactly what I was trying to say. Thank you for being more detailed and eloquent about it

I just wanted to get some confirmation that my thought process was sound.

 

[shredthrash]

Let me try again. The weight of 1 kilogram mass is always 1 kilogram on the earth's surface. You should actually also correct for altitude but since you're unlikely to brew on the Himalaya (and even there the difference in earth's gravitational pull is microscopic) we can forget about that. The weight of 1 liter of water changes with temperature. If your calculations (either performed by hand or with some software) ask for 20 liters of water, those will be 20 liters at 20°C (standard temperature). If you want to translate that into a weight measurement you have to consider the density at 20°C and multiply that by the required volume to get your target weight. From that point on since you're working with weight only you can ignore the actual temperature water has at the time of measurement, which could very well lie anywhere between 0°C and 100°C.
Of course the differences are very small but it's important that the principle is understood in order to avoid any pitfalls in future calculations.

And yes, all of my brewing water just gets measured on a calibrated scale (room temp RO water), that way I know exactly what my volume changes / losses are downstream (albeit needing to correct with SG after the mash, etc)

 

[shredthrash]

Sorry that I cannot help with the calculations, I just don't see the value. Why do you need to be so accurate? Seems like a solution looking for a problem to me.

As I've mentioned before, it literally makes my life easier. I use RO water. My buffer tank has 13 L capacity, so I just throw a pail on a scale and open my facet. No looking at graduations, no dipstick, no measuring cups. I literally open a faucet a look at a digital number readout. From there I can do simple (incredibly simple) math to know if I'm hitting any target I want to know that accounts for volume.

On the homebrew scale we already do SOME basic volume calculations (ex. Accounting for a 4% volume loss upon knockout and cooling due to thermal shrinkage) , but no, technically the accuracy gained on the small scale of home brewing will not make or break the QUALITY of your beer, but it depends what you're trying to get out of it...

Personally, I enjoy things such as this and I love learning new things and trying them out.

I work in a very large professional brewery and these volume calculations DO matter a huge amount (volume is measured with a pressure transmitter in the base of CCTs , wort kettle, whirlpool, etc. It is plain and simply the MOST accurate measurement method)

 

[shredthrash]

Easily solvable by measuring gravity. From a gravity measurement it's trivial to calculate actual boil-off and from that and the starting volume the current volume can be easily calculated.

Exactly

 

[Vale71]

Thank you for being more detailed and eloquent about it

That's an euphemism for anal retentive, right?

 

[Northern_Brewer]

If your calculations (either performed by hand or with some software) ask for 20 liters of water, those will be 20 liters at 20°C

The point is that measuring a volume at x°C and then converting it to y litres at 20°C means an unnecessary extra step.

From a brewing point of view what matters is the volume at mash temperature and/or boil - or at least, being consistent in those volumes. Look at it another way, what really matters is adding the same number of water molecules each time.

If you weight out 18kg of water, then you know that every time you're going to end up with 1000 moles of water in your mash in winter or summer. (Well OK, 18.015kg of water, subject to fluctuations in the Earth's gravitational field and variations in isotopic composition. But let's not go there...)

Whereas if you measure out 18 litres of water at 30°C or 3°C you're going to end up with a differrent number of molecules in your mash. Unless you correct for temperature, but that's just extra work and we're lazy, right?

Ultimately, while it's commendable to look at anything that will help the repeatability of your brewing, for me the variation due to measuring volumes at different ambient temperatures is small potatoes compared to other sources of variation (like my somewhat temperamental kettle). As it happens I do measure water by weight for accuracy reasons, but it's probably unncessary for me to do so.

Bottom line - whatever is easiest for you.

 

[shredthrash]

I think this is the way (get it?) to go if its easy for you.

For me it's difficult because it usually takes me about 16.5-17G of strike water. Not only is that a lot of volume, but it weighs a lot too. Less lifting is better for me.

I did a weight calibrated check (weighed water on a scale) against my sight glass markings once and it was reasonably close. Since these days i tend to repeat/tweak recipes more than I used to, i make really good notes about volume and gravity at various points and that helps to dial it in too.

Absolutely! The setup I use this method for is my 15 L BIAB setup and I have yet to use it for my 3 vessel keggle Brewhouse.

 

[shredthrash]

The point is that measuring a volume at x°C and then converting it to y litres at 20°C means an unnecessary extra step.

From a brewing point of view what matters is the volume at mash temperature and/or boil - or at least, being consistent in those volumes. Look at it another way, what really matters is adding the same number of water molecules each time.

If you weight out 18kg of water, then you know that every time you're going to end up with 1000 moles of water in your mash in winter or summer. (Well OK, 18.015kg of water, subject to fluctuations in the Earth's gravitational field and variations in isotopic composition. But let's not go there...)

Whereas if you measure out 18 litres of water at 30°C or 3°C you're going to end up with a differrent number of molecules in your mash. Unless you correct for temperature, but that's just extra work and we're lazy, right?

Ultimately, while it's commendable to look at anything that will help the repeatability of your brewing, for me the variation due to measuring volumes at different ambient temperatures is small potatoes compared to other sources of variation (like my somewhat temperamental kettle). As it happens I do measure water by weight for accuracy reasons, but it's probably unncessary for me to do so.

Bottom line - whatever is easiest for you.

I'm not looking at measuring water volumes at different ambient temperatures. When your recipe calculations call for a water volume, they assume a standard temperature of 20C ("room temperature"). My RO water is 20C. I weigh out 20 kg of water. Now, anything I do downstream in the brewing process can be calculated with great accuracy because I know my weight and downstream I can measure my gravity and temperature. These 3 variables are all you need.

 

[kevink]

One of your reasons for wanting to do this is accuracy, but do you know how accurate your scale is at 20kg (44 lbs)? The accuracy of your volumes are only going to be as good as the scale. Unless you have a 20kg calibration weight, how are you supposed to know how good the scale is?

 

[Pkrd]

Unless you have a 20kg calibration weight, how are you supposed to know how good the scale is?

You could just use 20l of water of course.

 

[kh54s10]

One of your reasons for wanting to do this is accuracy, but do you know how accurate your scale is at 20kg (44 lbs)? The accuracy of your volumes are only going to be as good as the scale. Unless you have a 20kg calibration weight, how are you supposed to know how good the scale is?

And I still don't see the need for such accuracy. There are so many variables in brewing that a quart of water +/- is not something that worries me.

 

[MuddyBrown]

One of your reasons for wanting to do this is accuracy, but do you know how accurate your scale is at 20kg (44 lbs)? The accuracy of your volumes are only going to be as good as the scale. Unless you have a 20kg calibration weight, how are you supposed to know how good the scale is?

That is a simple matter of weighing out 4 separate batches of 5 kg of water, assuming the scale is at least semi-accurate in this weight range. Really, all you care about is the scale is weight is constantly repeatable in its weighing capability. It does not matter if it is off by 100g or so from the true weight. Then you combine the 4 individual 5kg water batches into a single container, it should weigh around 20kg. If it is at the upper end of the scale limits, the accuracy may be off by ... 5%. I'm taking a guess.

 

[kevink]

And I still don't see the need for such accuracy. There are so many variables in brewing that a quart of water +/- is not something that worries me.

That's the fourth time that you said it's not worth it. I agree with you, but that's not the point of the thread.

 

[kevink]

It does not matter if it is off by 100g or so from the true weight.

It may to the OP since accuracy is one of his goals. I am very curious what he has done to ensure his scale is accurate as everything he is going for comes down to the accuracy of the scale.