Variances in corn sugar weight/density?

[tom777]

Is it common to have differences in the densities of corn sugar from different sources -- perhaps relating to how fine it's ground? The reason I ask is that everyone says to use 3/4 cup or 5oz. for priming a 5 gallon batch. However, 3/4 cup of the corn sugar from my LHBS only weighs in at 3.5oz. I've almost always used 1 cup as that's what the original instructions in my starter kit said to do and I was happy with the results. But, even 1 cup only weighs 4.65oz. I don't try to pack it in when I scoop up a cup full -- just try to fill it and level it off and that's it. I checked the scale I use by weighing a couple of the 5oz. packages of priming sugar supplied in the Brewers Best kits I've done and it seems to be right on. I guess since we should go by weight rather than volume, I'll stick with using around 1 cup for now since that seems to be working fine. Just curious if anyone else has run into this.

 

[DUCCCC]

Every time I've bothered to measure the volume vs. the weight I get about 4.75 - 5 oz to a cup, which is right in the ball park. It is certainly well within the the amount needed to safely carbonate a 5 gal. batch of brew. I have a simple analog scale, so I go by weight for my bottling amount. I think where you're going to really want to start weighing rather than measuring in cups is when you start getting really particular about exactly how many volumes you're priming to. Most brewing software apps have a calculator that gives a weight amount of dextrose for the specific fizz level you want, or that a certain style recommends.

 

[MikeFlynn74]

I think it all depends on how well its settled. Also improperly stored corn sugar can pick up moisture too.

 

[TheFlatline]

I think it all depends on how well its settled. Also improperly stored corn sugar can pick up moisture too.

+1

There's a reason why, in baking, there's a specification between "sifted" and "unsifted" flower measurements.

I go by weight 100% of the time now. You can find digital scales for less than 50 bucks, or in my case, I have a 2 pound analog scale I spent like 13 dollars on, and a 500 gram (it measures in ounces though) digital scale I can get *really* precise if I need to.

Also, the amount of priming sugar needed changes depending on how hot or cool your beer is at bottling. The difference of 5 degrees can be half an ounce of sugar or more.

 

[politovski]

ok,
the density of corn starch (ideally) is 0.33g/mL, so 500grams would be 1515mL, or about 6.4 cups, and 100g (for priming) would be about 303mL, or 1.28 cups.
cheers
p

 

[cimirie]

Not really trying to revive a dead post, but I've ben thinking about something lately that I remember from college chem labs. If a certain powdered solid (in this case corn sugar) absorbs moisture, its volume will increase. BUT if you measure the amount of a certain mass of "dry" powder and the same mass of a powder that has absorbed moisture, there will be less actual powder in the hydrated sample.

By that logic, weight isn't neccessarily a better way to measure corn sugar unless you and your LHBS are meticulous about keeping corn sugar in a cool dry place. Both methods have their faults. thoughts?

 

[944play]

If there's any question, just drop a hydrometer in your priming solution, or prepare a standard one. An ounce of dextrose dissolved in a cup of water should read 1.037 at the hydrometer's calibration temp.