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Well maybe I should have stated fermentation stage when there is no CO2 being produced so it takes 24 to 36 hours to produce top pressure.OK. Personally, I find Dr. Chris White's estimate of 3-15 is more realistic. And, seeing co2 coming out of solution may take longer. If you are using pressure to reduce esters, then you don't want to wait until esters are produced during exponential growth, to start adding pressure.
https://byo.com/article/fermentation-time-line/
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It's a closed system until there's positive pressure to over come the spring pressure behind the valve, that's the primary function of a valve, they open when required.
You know pressure fermenting reduces H2S, you've used the counter argument before that Chris White prefers lagers that haven't been overly pressure fermented and contain some Sulphur in the flavour profile. He's says as much in the above video at 30 minutes. He's even told you in person.
Without any pressure the yeast will clean up H2S given time.
The OP's question was about using a blow of tube when using the Blowtie spunding valve, the Keg Land link determines it is better to use a blow off tube with the Blowtie, and ferment as normal for 24 to 48 hours before applying pressure, Teri Farhendorf a head brewer suggest the same as does Chris White.
Entirely up to you when you apply pressure, but at least by adding the blow-off tube you are covering your bases regarding infection. The Blowtie is the cheapest diaphragm valve on the market and even though it isn't bidirectional a drop in fermentation temperature could cause a suck back, also without regular cleaning they can tend to stick and they do collect crud.Thanks again everyone - really useful discussion that I’ve not seen covering all these points in one place before. My takeaways against my 3 original questions are:
1. Don’t need a blow-off tube attached to the spunding valve unless the valve is fully open with no positive pressure from the fermenter side. But it doesn’t hurt to attach one as a ‘belt & braces’ approach.
2. Depending on your view of the length of the yeast’s lag phase, you can probably set the spunding valve to create pressure right from the start of fermentation.
3. Aim to start fermentation at the normal operating temperature for the yeast but if it’s a bit higher that should be OK.
Well they aren't lager without the lagering process. I am a great believer in Murphys Law so I try to leave nothing to chance, I don't pay for ingredients but on the two occasions I had an infection I got as mad as a cut snake. Not about ingredients but the time wasted.I have brewed many (50+) lagers under pressure in this way, I have never put the output from the spunding valve in sanitiser and never had a problem. The pressure is driving CO2 out so nothing can go in.
I have pressurised the fermenter and then set the spunding valve to the correct pressure and sometimes just let it do its own thing if I am sure the valve is set right, and again had no problems. I mainly use SafLager 34/70 yeast and maybe it's very tolerant. I have also put into the fermenter at 22degC and it has raised the temp to 24-25 with no real adverse effects.
I can't vouch for any other yeasts with this method.
I also just tip the yeast (2 packets in 55 litres) in the wort when pitching from my counter chiller and it's going crazy in 24 hours.
I tried pressure fermenting in 2017 by 2018 I had given it away, I found the quality of the end product lacking.
I have been in many commercial breweries around the world and unless they are using open fermenters I haven't seen one that doesn't use a spunding valve, or a blowoff tube for that matter. No they don't pressure ferment, they only use the spunding valve towards the end of fermentation to partially carbonate the beer saving money on the purchasing of CO2How can there be? Pressure is just a mechanism for suppressing esters and everyone has differing expectations.
Commercial breweries rarely pressure ferment because they want esters, they are a unique fingerprint of how their brewery and process shapes the taste and aroma of their beers. The general public either like it or they don't.