When is a gallon not a gallon?

I am confused. I used an empty milk container as a measure for a gallon and it comes out 1/3 of a cup short even when filled to the top. The milk container states 1-us gallon or 3.78 litres. I used a liquid measuring cup for the measurment. So I went back to the store and bought a plastic pitcher that has a one gallon mark on it. It measures out the same as the gallon of milk-short 1/3rd of a cup?

What is anyone else using for a one gallon measure that is accurate?
Any help is appreciated....cheers

I have a 1/2 gallon measuring cup. But now I use anything I have free to measure the depth of liquid in my brewpot. I made a spreadsheet relating depth of water and volume for my brewpot and so now all I have to do is measure depth. So I can avoid pouring 1/2 gallon after 1/2 gallon.

Of course there is also the 4% volume difference between water at varying temperatures...

Weigh your water. 8# is a gallon.

dirtylarry said:

Weigh your water. 8# is a gallon.

Click to expand...

8.33 pounds per gallon at room temperature, 8 pounds per gallon at boiling, or about 8.15 pounds per gallon at mash temperature.

So I googled a gallon of water and found weights by water temperature and such, but I am still confused because a gallon of milk is still short 1/3rd of a cup when I use the same temp water. Also my brew pails are marked at 1,2,3,4,5 gallons and they all come up short when you fill it by using a milk container! I am using a liquid quart measuring vesel.I guess the important thing is to use the same container for all brewing and adjust your recipe's accordingly!

mnpaddler said:

..an empty milk container as a measure for a gallon and it comes out 1/3 of a cup short...

Click to expand...

I'm sure my precision leaves something to be desired, but I pretty much don't measure anything in my batches that precisely. I prefer the RDWHAHB approach. If you're into anal precision (I understand, I am about somethings) a gallon contains 16 cups, so being a third of a cup short's not likely to ruin a batch of your current project (it's only a little over 2% off).

As to the recommendations about weighing, buying other items I'd say screw that. The point of measuring is to obtain known quantities. If your milk jug is 1/3 cup short, add the difference to your pot/carboy etc. I couldn't see buying something (especially not dragging out a scale and temperature conversion matrix chart!) when the FREE jug on hand does the job.

Your mileage may vary, but I'd suggest simply relaxing about it. Add the excess manually if it worries you. Or buy something more precise if you've got the money to spend.

I've never calibrated my equipment because for what I've done so far, "ball park" is close enough and has allowed me to replicate (at least to my amateur palate) what I've tried to.

Mals

Your question is weight v/s volume. 1 cup sand -1cup flour-1 cup sugar will all weigh differently. And depending on the time of year they will also vary. 1 Gal in weight is 128 oz. But when you add anything to the water. Per say weighing wort it will be heavier. So if you wanting to get close you would only consider volume not weight.

1 gallon= 128 liquid ounces= 4 quarts. If you're getting shorted by your milk producer, let them know. Or double check your liquid measuring cup, as that is the one that seems to be off.

The markings on the pails are WAY off. The gallon jugs you buy could be anything - don't trust them.

If you want to be exact, there are several options. If you want to go with the flow, estimates are fine too. Find something that works for you but don't trust market-bought gallons or arbitrary markings on pails - just an FYI my markings were all off by 1/4 to 1/3 gallon.

Also milk containers hold and are capped most times with more than one gallon.

YES some of the pails are off. If you have available a scale. you can weigh and mark accordingly.

mnpaddler said:

So I googled a gallon of water and found weights by water temperature and such, but I am still confused because a gallon of milk is still short 1/3rd of a cup when I use the same temp water. Also my brew pails are marked at 1,2,3,4,5 gallons and they all come up short when you fill it by using a milk container! I am using a liquid quart measuring vesel.I guess the important thing is to use the same container for all brewing and adjust your recipe's accordingly!

Click to expand...

A gallon is 231 cubic inches, so if you have a container big enough to hold a gallon you can divide 231 by the length and then by the width to find the height that you need to fill it to get one gallon. But you need a container with sharp edges and corners on the inside because if they are rounded it makes it very difficult to know how much that detracts from the volume.

DeafSmith said:

A gallon is 231 cubic inches, so if you have a container big enough to hold a gallon you can divide 231 by the length and then by the width to find the height that you need to fill it to get one gallon. But you need a container with sharp edges and corners on the inside because if they are rounded it makes it very difficult to know how much that detracts from the volume.

Click to expand...

Just do pie r squared times hight will give u the volume of a cilinder

mnpaddler said:

I am confused. I used an empty milk container as a measure for a gallon and it comes out 1/3 of a cup short even when filled to the top. The milk container states 1-us gallon or 3.78 litres. I used a liquid measuring cup for the measurment. So I went back to the store and bought a plastic pitcher that has a one gallon mark on it. It measures out the same as the gallon of milk-short 1/3rd of a cup?

What is anyone else using for a one gallon measure that is accurate?
Any help is appreciated....cheers

Click to expand...

How do you know the measuring cup isn't off? What size is the measuring cup?

Primevci said:

Just do pie r squared times hight will give u the volume of a cilinder

Click to expand...

Yeah, you could use a bucket, but the sides of most buckets aren't perfectly vertical - I suppose I could work out a formula given the dimensions, but I've had a couple of homebrews to celebrate finishing my income tax return, so I'd rather just RDWHAHB.

OK, so I have checked several milk container companies and find that they chill the milk prior to bottling-so if you let the gallon adjust to room temperature it should re-coup the missing 1/3rd cup! Just as your brew kettle will measure a larger volume of wort when it is hot than it will once it cools down. I use a 16 gallon keg as a brew kettel for 10 gallon batches. I found that cooling from boiling to 60F reduced the volume in the keg by 1/2 of an inch! I guess the imortant thing is to use the same volume each time and adjust your recipie's accordingly...cheers and thanks for all the response....