Adjusting priming sugar to specific gravity

Post #1 made 5 years ago
17 days ago I brewed 50 litres of the famous BIAB amarillo APA. After putting it in the fermenters it didn't really show much activity, which I am putting down to a leak some where on the fermentation buckets which is letting out the pressure somewhere. I'm not really worried that it hasn't fermented because there is yeast action but I can't tell if it has stopped or not. So I have some questions...

What should the final gravity of the Amarillo APA be? It was 1.058 into the fermenter.

How many grams of priming sugar should I add for priming? Yes I will be bottling it into l bottles and using table sugar from sugarbeet. Last time I added about 8 gr per litre and it came out about right. I don't particularly like a massive head on my beer.

Unfortunately my beer is at a friend's place so I can't measure the gravity right now but I'm wondering is there any way of calculating how much sugar I should add if it has a higher gravity than it should. For example if I measure the gravity before bottling and it shows 1.018 (and the final gravity should be about 1.012 - this is a guess too), how much should I reduce the priming sugar to take this into consideration and the bottles don't explode or have excessive head? So, does anyone know how much sugar contributes to specific gravity? Is it a simple linear relationship or is it much more complicated?

Are there any calculators which might help me?

Any input would be greatly appreciated.

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Post #2 made 5 years ago
Hi there jube,

50 L should keep you going for a couple of days :P.

Final gravity depends on a lot of things and so it is hard to predict. At 17 days though, even if you had the fermentor at 15 C / 59 F, that beer will be done. It could be anywhere from say 1.018 and lower. Only way to know when FG has been reached is by seeing when the gravity stops falling. Rather than taking daily samples, just take one sample say 7 days into fermentation. Make sure you have a nice wide hydrometer jar, leave your hydrometer in it and cover it with plastic and leave it near the fermentor. That way, every few days, yo can lift the plastic, give the hydro a spin and check the gravity.

Now as for the priming sugar...

Your final gravity has no bearing on how much priming sugar you should use as your fermentation has already eaten up any sugars it could. So FG does not affect priming sugar rates.

Secondly, you don't use priming sugar to increase alcohol content otherwise you will blow yourself up :argh: . The only job of priming sugar is to carbonate the beer, nothing more, nothing less. So, if you were happy with 8 grams per litre on your last batch of this beer, then use that again.

(The only thing you can do with priming sugar is lower the alcohol content of the beer by dissolving the priming sugar in boiled water and then bulk priming. Depending on how much water you add, you could either keep the ABV the same or lower it but really you only want enough water to dissolve the sugar. If you are adding priming sugar directly to the bottles, as a ball-park figure, this will increase the ABV by about 0.2%.)

There are priming calculators out there but most of them disagree with each other. We are currently trying to find the best options for the BIABacus but for now, stick to your 8 grams per litre. Looks fine to me for this beer at ale fermentation temps.

Last edited by PistolPatch on 17 Aug 2014, 19:31, edited 1 time in total.
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Post #3 made 5 years ago
Hi PP,

Thanks for your answer...I just managed to measure my FG and it is down to 1.010 so it all looks like it is ready for bottling tomorrow. :-)

It smelt great too... I've only had one offish batch but its always a relief to open the fermenter and be greeted by the Amarillo aroma.

Thanks for the tip about having a separate vessel for measuring FG.

Brew on :-)
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