First BIAB - Help me understand the numbers

[SBOB]

So yesterday was my first BIAB attempt and I think it mostly went to plan..Did the All Amarillo APA based on the BIABacus spreadsheet over on that biab forum...

Did a 90 min mash, stirred while bringing up to 78 degree mash out then a 90 min boil.

Few areas where i missed the 'estimated' mark, but only slightly so I think it went well..
Any thoughts on the following areas where I didn't match the predicted outcomes:

Overshot on my strike temp a little with the mash starting around 67/68 (started at 67 but after wrapping the urn up the temp rose another degree).. so ended up with a 90min mash going from 68 down to about 66.5 degrees.. So, will know for next time to try a little lower on my start temp.. My insulation + sleeping bag around the urn definitely kept the heat in..
- Will a slightly higher mash temp have any negative effects?

My evaporation was less than the BIABacus predicted with only around 4.3 litres lost from my starting 'Volume into Boil' (VIB) instead of the esimtated 6.18..
This meant I ended up with an OG of 1.050 instead of the predicted 1.056 and an extra couple of litres above the estimated 'Volume of Ambient Wort' (VAW)
- Is a lower level of evaporation an issue? Im using a Birko 40L urn so the wort was definitely boiling but was not a vigorous boil..

Dumped the liquid into a no chill cube for pitching next weekend (fermenting fridge is currently crash chilling something else), so won't know the exact volume of wort into the fermenter until then but it smelt good

 

[warra48]

1. Your mash temperature was about spot on at the mid point of the range, so you will be fine and suffer no negative effects. To lose only 1.5ºC over 90 minutes shows your insulation is doing an excellent job.

2. The lower level of evaporation from the predicted will result in a slightly lighter beer with a little lower alcohol content. Nothing to worry about, as 1.050 is still a good OG. Your beer should turn out fine.

Your experience with your first brew just shows that each brewer needs to take software predictions only as a starting point, to be modified by your own experience with your set up. Next brew try boiling a little harder and see how you finish up.

I wish you well and hope it turns out as well as the smell did when you cubed it.

 

[SBOB]

Next brew try boiling a little harder and see how you finish up.

well the Birko was on 100% so if i need to increase the evaporation rate it would require a longer boil

 

[warra48]

You can't do better than 100% with the Birko, so boiling harder obviously isn't an option.
Maybe drop the mash in volume slightly to allow for it?

I don't BIAB, I'm a 3V brewer, so anyone with better knowledge of BIAB will hopefully jump on board for you.

 

[yum beer]

Maybe look at dropping your initial volume by a few litres so you can boil harder then top up with cooled boiled water into the FV.

A pie tin floating on top can help as well.

 

[schtev]

A pie tin floating on top can help as well.

First I've heard of this technique. Is the idea to keep more heat in the pot?

 

[RdeVjun]

Some discussion about floating a dish to improve boil performance. Oh and here's some more, this one's a bit lively with more robust exchanges of ideas. Ahh, those were the days... B)
Anyway SBOB, FWIW there may be some boil improvement with a dish floating on it. Oh, presume the insulation was still in place for the boil, leave it on if you can? You wouldn't be the first to tackle urn boil performance issues, AFAIK its been overcome with relative ease.

As the spreadsheet authors would relate, you can use it to dial in your system and compensate for its particular characteristics, nevertheless you've had a fairly decent result for a maiden BIAB- nice one and keep going! :icon_cheers:

 

[philmud]

Also be aware that lower evaporation rates are not the only affect that a gentle boil can have. Boiling also evaporates compounds like Dimethyl sulphide (DMS) which can give your beer an unpleasant boiled corn flavour. Many brewers advocate a more rigorous boil to ensure as much of this compound is driven off as possible. Pilsner malts are especially high in DMS precursors, and a 90 minute boil is often recommended where a pilsner base malt is used.

 

[ianh]

The fact your mash temperature went up suggests that the water was not uniform in temperature, needs to be vigourously stirred whilst measuring the temperature.

I use a 40 L concealed element crown urn and average 3.5 litre/hr boil off (5.25 for 90 mins). Birko should match or slightly better this. 10-15% is a recommended boil off rate

 

[Donske]

I personally don't like the floating dish thing, kept having them turn over in the boil.

What I do now is make a cone out of alfoil that fits around the top of the kettle with a ole to vent the steam, similar to BM hoods you can get for those things to improve boil vigour.

Works a treat but does take some dicking around to make sure any condensate that catches on the alfoil runs down the outside of the kettle.