Good question.
I cure 8 pounds of meat or more quite often. From my experience I know that 1 gallon of water should have no problem covering 1 pound of meat so it was just a "sure nough" measurement to know you would be covered provided you aren't using some giant rectangular shaped tub to cure/brine in lol.
In reality you use just enough water to cover your meat by a couple of inches, BUT figuring out how much water that is and how much that water weighs can be a bit tricky.
I figured that would be lesson 2 of your equilibrium cure/brine adventures :D
I have a simple method to figure it out though.
In short put your meat into your cure/brine bucket or tub.
- Measure out 64 oz of water and pour it in
- Repeat measuring out 64 oz and pouring it in and write down how many times you do this so you know how much water was added
- STOP adding water when you get to a point where you know one more 64oz pitcher of water is going to cover the meat and give you 2 inches more water on top
- Add up how many 64oz pitchers of water you have added plus the last 1 you have not poured in it. Multiply that number by 1,890gms and that is how much your water weighs :D (64oz is half a gallon and half a gallon weighs 4.1667 pounds which = 1,890gm)
- Finally, measure out your salt and cure and sugar based on Meat Weight + Water Weight = TOTAL WEIGHT (omit cure if not using it, omit sugar if not using it). Blend some of that final 64oz of water and some of the salt, sugar, cure in a blender and get it partially dissolved (may take a 2-3 loads of water and salt, sugar, cure in the blender)
- Pour that dissolved stuff into the bucket/tub and repeat that last blending step until the final 64oz of water, salt, sugar, and cure are all done and poured into the bucket/tub
- At this point you can swish the solution around and start injecting it into the meat if doing injections :D
This method lets you figure out how much water you needed and how much it weighs no matter what your bucket/tub shape or size is AND allows you to accurately calculate your salt, sugar, cure!
So, to recap. I knew 1 gallon of water should have no problem covering 3 pounds of meat so it was a heavy handed solution.
In reality some one would use the most accurate solution and minimal amount of water, salt, sugar, and cure needed but they have to know the tricks to getting this all sorted out which I'm sure you will be ready for very soon but you are armed with the ability to move on that 3 pounds of meat right now using the 1 gallon of water and the numbers provided :D
Let me know if this answers your question well :D