Jun 202130Wed

Started Divoká Šárka – Czech Lager

SG 1.047 22.1℃ started

I’ve wanted to try brewing a lager for a long time now, but was always hesitant to try because of the lengthy lagering process involved. Recently I saw a recipe on Brewfather from Gavin Ellicott (YouTube’s Gash Slugg) for Czech Lager using a familiar fermentation method, and it looked pretty easy. Time to have a go.

Brew Day Entertainment – Revising for my Amateur Radio exam

Brew day went pretty well, and for the first time ever I was close to getting the numbers I had hoped for, though if I’m honest I did cheat a little bit by rounding up my mash and sparge water quantities (21.79 and 9.75 respectively) to the nearest litre, and then tilting the HLT at the end of the sparge because that stage once again passed by very quickly.

Mistakes were Made

The only fly in the ointment was an error I made when transferring the wort to my Fermzilla. My usual process is to switch on the counterflow chiller at the end of boil / hop-stand, monitoring the return temperature instead of the tank temperature. Returning wort from the chiller is much cooler than the tank and typically reaches transfer temperatures of around 20 – 25℃ when the tank is still at 50 or 60℃, depending on the temperature of the mains water used for chilling and the speed of the pump. Once I saw that the return temperature was 23℃, the same as my yeast starter, I turned the upper left-hand valve to send the chilled wort to the Fermzilla via my newly fitted Bouncer filter instead of sending it back into the kettle. Or so I thought. I actually got the setting wrong by 180° which resulted in the return flow from the chiller being shut off entirely, and instead started draining the kettle into my FV.

I should have noticed that the flow was quite high despite the moderate pump setting, that the return temperature was slowly climbing, and that the Fermzilla was warming up, but I was too focussed on the clarity of my wort and making sure that the Bouncer filter didn’t leak because I hadn’t tested it since hastily fitting tribute-clamps. Once I realised my mistake it was too late, and I’d filled the FV with wort at 45℃, a good 20℃ more than I’d wanted. I thought about pumping it back into the kettle somehow and repeating the chilling process, but then I remembered that the recipe I was following also didn’t use a chiller, though that was due to water shortages in Australia at the time. In the end I decided to put the FV into my fridge and chill it to pitching temperature gradually instead of worrying about it too much.

On a Positive Note

The Bouncer filter worked quite well and didn’t leak, which means my PTFE tape did its job. I’ll be using it again next time round, but may switch to the finest filter. Using the medium grade filter didn’t catch as much trub as I was hoping, but that could well have been to the 30 minute hop-stand / whirlpool causing everything to settle in a rough cone rather than leaving it in suspension.

Brew Day Notes


07:35 Start mash-in. Using 22 litres mash water and 10 litres sparge water.

07:45 Mash-in complete. Looks pretty thin compared to my previous brews.

08:05 Mash started, first stir. Looks thin in terms of grain density, but its surprisingly cloying and there’s no chance of getting the flow to ‘fan out’ just yet. Mash volume looks like 25 litres, exactly as Brewfather predicted.

Milky Mash

08:45 Second stir. Wort seems almost clear before, during stirring it’s full of suspended particles but not as milky as it was at the start. Seems to flow better too, though I’m still not able to fan out without sucking air.

09:04 Third stir. No drama, bit milky afterwards.

09:13 Sucking air, reducing flow inside centre pipe. Not stirring again – I want a nice slow sparge.

09:21 Mashing complete. Turn off centre pipe but leave pump and heaters on, let it settle for a few minutes in order to measure mash volume and gravity: 25.75 litres, 1.063 (1.045 @ 63.5℃)

09:36 I’m raising the malt pipe for a bit of vorlauf to get rid of the last few floaters while my sparge water heats up. No reminder from Brewfather this time, must check the settings.


09:43 Ran vorlauf until elements are exposed, wort runs clear and no floaters. Starting sparge now that level’s an inch above grain bed. No tin foil hat this time.

09:49 Sparge complete, letting it drain for a minute or two while I take another gravity reading. I tilted the HLT a little towards the end as I always seem to be short of water and my sparges don’t last as long as I’d like. Volume now looks like 28.75 litres, which isn’t too bad against Brewfather’s predicted 28.86. Pre-boil gravity 1.046 (1.030 @ 61.5℃) against Brewfather’s predicted 1.044. Happy with that.


10:25 Boil started at 99℃, 60 minute additions in, steam hat fitted.

11:30 Boil finished, all additions are in. Reducing to 80℃ for hop-stand.

60 minute additions

11:35 Starting hop-stand tracker, 30 minute additions in. Going to use this time to try and rig up some tri-clamp fittings for the Bouncer filter.

12:02 There’s 5 minutes left on the hop-stand and levels are 26.5 litres at 79.6℃. (Brewfather predicted 26.45 – nice) Bouncer filter successfully adapted, plumbing into transfer line.

12:09 Hop-stand over, start chill. My yeast starter is at 23.9℃ (supposed to be no higher than 22 – oops!) so that’s where I’d like the chiller return temperature to be before I start transfer.

12:17 Check post-boil gravity while I wait: 1.047 (1.028 @ 65.1℃) which is just one point below Brewfather’s 1.048. Happy with that.


12:23 Return temperature now reads 22.7℃ so let’s start transfer. This time I’m going 100% to out-pipe, not making that mistake again!

12:39 Oh shit, I’ve cocked up again. Incorrect setting of the upper left-hand valve meant that instead of feeding my chilled wort to the fermenter, I was draining the hot kettle directly and running the pump against a blocked chiller. What an enormous tit! The increasing return temperature should have given it away, but I was too engrossed in my lovely clear wort. Oh well, the original recipe also said ‘no chill’ so I’m hopeful she’ll be right, Marv. Into the ferment fridge and dials set for 22℃, presently 43.8.

13:55 Cleanup finished, fridge at 40.8℃

22:00 Chilled in ferment fridge to 22.1℃ from 40.8℃ in 8 hours. Nearly had another heart attack on opening the fridge – volumetric contraction had put a large dent into the Fermzilla because I neglected to pressurise it beforehand and had the lid on airtight. Idiot. Popping PRV fixed it, let’s hope there’s no damage to the vessel’s ability to function under pressure. The wort was aerated for a minute using bottled oxygen, deployed blue Tilt Pro, then pitched my yeast starter and fitted spunding valve. I’m leaving it fairly low until fermentation gets started, will then dial up to 10 PSI. Fermentation schedule calls for 5 days at 13℃ so I’ve dialled that into the Inkbird and set her off. Fingers crossed!