After experiencing midnight explosion in 5L keg few year ago, i researched for safer ways to prime. Ever since i was measuring dextrose and adding in each bottle per its volume (and desired CO2) and filling up directly from the fermentation container.

I started to wonder if there is a shortcut and if this technique is considered sterile.

After much reading, i find many people use a bottling bucket to add sugar/dextro in a batch after boiling.

I do have an extra container but without spigot and without auto-siphon.

  1. Any tips for other ways to add the priming sugar in a sterile way (and easy)

  2. Isnt it an issue to fill up 5L kegs, 0.5 and 0.33 from the same batch with the same amount of sugar/dextro?

  • Have you thought about using carbonation tablets? May 28, 2019 at 22:15
  • i have few from an open pack of last year. i wouldnt use them.also its hard to add the exact amount i want to reach May 28, 2019 at 22:27
  • I just add about a quarter of an espresso spoon per Grolsch swingtop pint bottle.
    – Robert
    Jun 3, 2019 at 17:46
  • IMO, doing it bottle by bottle is harder and riskier. you are measuring a very small quantity and it requires a good deal of accuracy and precision. I have always primed the entire batch and bottled from there.
    – uSlackr
    Jun 18, 2019 at 16:51

2 Answers 2


It's easy to overprime a 5L mini-keg. They only need 1 tablespoon sugar to prime, which is much less than an equivalent 5L in various bottle sizes. This is because the amount of head space in a keg is much different than the neck of a bottle.

For bottles, I always bulk prime with 2 tablespoons sugar per gallon. This will rarely overcarbonate, only if fermentation was not 100% complete prior to bottling. I boil the sugar in about 2 cups water, then cool, then add to the bottling bucket, or I guess you could add to the fermenter if not using a bottling bucket. You can use whatever size bottles you like, it makes no difference, they will all carbonate the same.

For 5L kegs, I still boil the 1 tablespoon of sugar in about a 1/2 cup of water, then rack the beer into the keg. Then allow 10 days or so to carbonate, same as bottles.

Hope this helps.

  • Thanks for your answer, i now understand the complication with this 5L party kegs. I am hesitating to add the sugar solution directly into the fermenter as i will need to mix well and there is good chance of oxidation. May 29, 2019 at 11:05
  • IMO, priming should be done based on weight of the sugar - not by volume.
    – uSlackr
    Jun 18, 2019 at 16:52

After considering all the options i've decided to continue add sugar directly into each bottle (per kit instructions) but in a more sterile way:

I will add the 102gr sugar into 100mL of water, bring to boil and then cool it down. Using syringe i will dose per the following math formula:

102gr = 100mL (102gr sugar added to 100mL of water)

100mL * 0.5L / 22L = 2.27mL for each 0.5L bottles

100mL * 0.33L / 22L = 1.5mL for each 0.33L bottles

Thinking of beer kits, their usual instructions are not 100% sterile as they always recommend to add 20~L of un-boiled water, in addition to adding un-boiled priming sugar.

  • Don't worry about sterile too much. Your beer is already fermented, it has hops, alcohol, and a low ph level. All these make it less likely to spoil. If you use household-clean equipment, you should be fine.
    – Robert
    Jun 3, 2019 at 17:45

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