Brewing in Plastic PET Bottles and how much to prime?

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tonyp
Posts: 7
Joined: Wednesday Jan 11, 2006 12:49 pm

Brewing in Plastic PET Bottles and how much to prime?

Post by tonyp »

G'day guys,

Been looking over the forums and sites and have not found the answer to this question yet so if anyone can help (or point me in the right direction) that would be great.

I have been making experimental batches of cider and ginger beer in plastic soft drink bottles (I know that this can be a sin in itself :) ).

When priming them i have been using the same ratio as in a 750 ml glass bottle. (1 teaspoon per 750 mls.) Ie. 2 tsp for 1.5 litres etc. I have found that this results in too much pressure due to the amount of sugar placed into the bottles.

Is there a formula that reduces the amount of sugar as the size of the container goes up? ( i assumed it was linear due to 1/2 tsp being used in a stubbie and 1 tsp in a 750ml) How much sugar should i place into a 2l and 1.25l bottle?

Cheers

Tony
Chris
Posts: 3716
Joined: Tuesday Oct 04, 2005 1:35 pm
Location: Northern Canberra

Post by Chris »

There is no reduction in the amount of priming sugar used as the container goes up, but an increase. This increase is linear.

The problems that you are having with too much pressure may be due to the bottles being inappropriate for the pressure, or that your brew has not fully fermented. If the later is the case, you would be advised to let it sit in your fermenter until you get two identical hyrometer readings, or rack it.
tonyp
Posts: 7
Joined: Wednesday Jan 11, 2006 12:49 pm

Post by tonyp »

The fermentation was finished and the containers were plastic PET bottles which can take a lot more pressure than glass.

They bottles were way too fizzy. I think i will experiment with it.
The problems that you are having with too much pressure may be due to the bottles being inappropriate for the pressure,
Can you explain this please??
Skoti
Posts: 27
Joined: Saturday Oct 08, 2005 9:16 am
Location: Auckland

Post by Skoti »

Sounds to me that they weren't ready to be bottled maybe a bit more time in the fermenter was needed .
I've never made cider or ginger beer but I do bottle into PETs .
When I prime I go by the rule of 1 tsp per 750mls-2tsp per 1.5-3 tsp per 2.25 and have never had any trouble .
I'm on a special alcohol diet ,
It's really amazing ,
I lost 3 days in the first week ! !
yardglass
Posts: 1072
Joined: Sunday Oct 09, 2005 7:40 am
Location: Brewing in the Shed.

Post by yardglass »

Skoti wrote:Sounds to me that they weren't ready to be bottled maybe a bit more time in the fermenter was needed .
exactly what i was thinking, my last Ginger Beer took 17 days with EC-1118 Champagne Yeast.
excuse me... your karma just ran over my dogma.

GOOD BREWS
Chris
Posts: 3716
Joined: Tuesday Oct 04, 2005 1:35 pm
Location: Northern Canberra

Post by Chris »

Soft drink bottles have thinner skin than say Coopers PET. This is simply because they are not designed for re-use.

As a result, they expand the plastic a few millimetres outward. When you come to open them, the bottles contract back (as the pressure is released), and force the contents out the top- fountain-style.
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