How precise must the measure of priming sugar be?

Question

I usually bottle home brew into 750ml bottles, and less commonly into 375ml bottles. I have a two-ended sugar spoon which is for priming these, and it's obvious which spoon head goes with which bottle (full spoon, half spoon).

I have collected a number of 500ml bottles and I wonder if I need to get the in-between proportion right for the priming sugar, or can I just pick one or the other safely? Should I use the half spoon for a 500ml since it's closer to 375ml than 750ml, or the full spoon? Should I get more spoons?

Does it matter?

Answer 1

It has to be pretty accurate, atleast within the general area. Priming a 500ml bottle with the same amount as an 750ml bottle will definately affect the outcome. That's 1.5 times as much sugar.

But I don't see why you do it that way at all.

When I prime my bottles, I weigh out an appropriate amount of sugar - say 150 grams for 25l. Then I get a deciliter of the beer, or water if I'm lazy and dissolve the sugar in it. Over heat if necessary. Then I just pour it into my fermenter and mix thoroughly.

Of course, this assumes you can rack to a secondary fermenter so you don't disturb the trub. This is no problem for me, I'd recommend you get a fermenter and mount a tap on it - makes bottling that much easier, if you use a "bottling tube". If you've already got that set up, then just follow the preceding paragraph.

Answer 2

In general, I'd say get more spoons for several reasons. First, the two sizes you have means that you will get the same number of volumes of CO2 in your beer, no matter the style. So your brewery will deliver, for instance, a stout and a saison that have the same carbonation level. And then the second, obvious reason is that you'll have a spoon sized to the new intermediate bottle size.

To decide how much priming sugar you need, you can put "priming sugar calculator" into your favorite search engine and use one of those. You will need to know how many volumes of CO2 is appropriate for the style. And you will probably need to do some math and a few conversions to get it down to a measuring spoon scale. By the way, you can type something like "2 cups in cc" into Google and get "2 US cups = 473.176473 cc". It's like magic!

As mentioned by Max, you could save on the detailed measurement by bottle by priming the entire batch at once. But that is not your question. I understand that it might be more of a pain to have an additional racking operation (which also opens up oxygenation and contamination risk), besides needing to buy or at least cleaning another vessel, etc.