mrrm1st wrote:Is there any benefit to using an immersion wort chiller over and above cooling the stock pot in cold water in the sink etc or is that not really too important?

Both methods are fine. An immersion chiller will cool your wort faster than an ice bath and I doubt you'll see much improvement with using both at one time. So for the sake of simplicity, if you have an immersion chiller I would just stick with that technique only. If you don't have an immersion chiller and don't want to spend the money on one, then an ice bath is just fine too.

mrrm1st wrote:I came to this site specifically to get a better understanding of maxi-BIAB. Having the maxi-BIAG guide in a sub-forum titled "Mini-BIAB" is a little confusing.

Good suggestion. The amount of people using the maxi-BIAB technique seem to be growing considerably, so it does make sense for it to have its own sub-forum. Maybe the mods can work on that.

Hi Bruce, it's a bit hard to answer your question without actual figures but here goes;

Assuming you have 12 litres (about 1/2 a willow container?) of wort at 1080, diluting with 10 litres of water will give you an OG of 1044. Diluting with 8 litres of water will give you an OG of 1048.

Hope this helps.

Sounds like it all turned out well Bruce.

Keep us posted on how it turns out.

First of all I'll say I have never done Maxi-biab, so take my advice with a grain of salt.
I would personally try to keep the kettle topped up as much as possible during the boil, and use as little fermenter top up as possible. Also, I wouldn't add any top up water to the boil after 10-15 minutes left in the boil.
This is just my own preference, and the way I intend to do my double batches in my 50L keggle in the near future.
Hopefuly Ralph will reply, as he has done many a batch using Maxi-biab.
Hope this helps,
Cheers wiz

Folks, I'll have to be brief as I have to fly into work, things have gone to sh*t again with our telemetry so I have to stop the sky from falling on our heads!

Yes, my rationale with Maxi is to have the kettle as full as possible all the time, but rather than use plain water I use it as sparge, that way it is put to constructive use. Evaporation can also be made good by adding excess sparge, thereby squeezing even more SG points into the kettle, but it should be pre- heated (microwave!) or else it pauses the boil. Don't add it after say 20 minutes, it really needs a good boil to be sanitised.

So Bruce, use that top up water for some good by dunk sparging!

Jonesy, that sounds pretty good to me, well done! A bigger bucket is probably desirable though, I just wanted to keep the method within everyone's reach so used very common equipment. A 15L nappy bucket would be good too, may be able to do it in one step.

Hope this helps, cheers everyone!

Maxi-BIAB Calculator that I've been working on
http://www.biabrewer.info/viewtopic.php?f=21&t=595

Useful for those who want to do double/triple batches using Maxi-BIAB principles, or for those who just want a few numbers and predictions along the way.

wizard78 wrote:First of all I'll say I have never done Maxi-biab, so take my advice with a grain of salt.
I would personally try to keep the kettle topped up as much as possible during the boil, and use as little fermenter top up as possible. Also, I wouldn't add any top up water to the boil after 10-15 minutes left in the boil.
This is just my own preference, and the way I intend to do my double batches in my 50L keggle in the near future.
Hopefuly Ralph will reply, as he has done many a batch using Maxi-biab.
Hope this helps,
Cheers wiz

The best reason to top up during the boil as much as possible is you dilute your kettle trub, which means you end up with more sugars in your fermenter

Yeah, that's certainly one good reason stux! Its also another good reason to add any sugar (if to style) to the fermenter and not to the boil.

FWIW, I get the feeling there's a few planets lining up with Maxi-BIAB, when delving into the numbers a bit, I find it is unlikely to use the technique to do a no- sparge/ plain boil- topped/ post- boil diluted (!!!) beer of much more than mid- strength. I know it hasn't been suggested, however for example, it isn't as simple as just adding more grain, for doing that, while it increases the runnings SG, it also reduces the wort yield because the mash volume is limited by the kettle. I'm mainly speculating here as I haven't tried that, but looking back over numbers from a few dozen batches, that seems to be the indication. [Probably a bit OT, but just an observation.]

Yes, my own experiences concur

As the gravity of the mashout liquor goes up, it becomes harder for the syrup to self-wash off the grain as you pull the bag, necessitating sparging/squeezing if you want to get above, say 75%.

doing a mashout reduces the thickness of the mashout liquor which helps it run of the grain, then the you squeeze it out, and then you rinse the grains... and that's the sparge.

Its all quite logical really

The big trick is not to over-sparge and end up with more liquid that you can fit in your pot, or boil off

Hi Dan and welcome,

I'd stick to Ralphs method, I can't see any advantage in pouring the wort off the grains when its easier to remove the grains from the wort. Plus whilst your sparging the grains in your bucket you can wack up the heat and start boiling your wort.



Yeasty

Good advice from yeasty there Dan, I'd stick with that.

There is no advantage to the other method that I can see. At least Ralph's method gets the bulk of the wort near to boil while the grain bag is being sparged. So a saving of time and gas.

It would make more sense if you were going to dunk sparge, but you'd still need to heat up the dunk sparge water after transferring, in which case you might as well use a boiled tea kettle to sparge in your bucket

Yep, nothing much to add that our brains trust hasn't already noted regarding sparging in the kettle and how that slows down the process, so just a couple of fairly minor things.

An oven is fine for maintaining temperature, but I would rather leave the kettle in place. In my circumstances it is going to be moved to the floor for lautering, however some brewers may leave it on the stove for the whole process. Leaving it in place usually means deploying insulation during the mash and I'm glad he noted that some insulation does work rather well in maintaining mash temperature.
I'm of the opinion that a great deal of energy is consumed in making beer, some insulation is one way to reduce that, if only by a relatively small amount, but it also achieves mash temperature stability, so it is really win- win. (BTW, passive lagging also works brilliantly when pre- heated.)
One other note regarding insulation is that the lid does need covering as well. Covering the whole thing will also mean less temptation to continually open the lid to stir or check temperature or both- neither are necessary after the 10 minute check and will just lead to additional heat loss without gaining any amazing benefits.

Importantly, just on the process shown over there at homebrewtalk, it doesn't seem to be post- boil diluted, therefore brewlength is limited by kettle volume. You'll note he split the grainbill into two and did it all twice- that's a lot of work for one 5gal batch. Maxi-BIAB isn't limited like that, it can do it all in one pass and is the major motivation underlying the method.

Oh yeah, there is one more thing- never crack a beer before the first hops addition goes into the kettle during the boil! I sometimes bend this rule, but usually regret it by the end of the brew day, as once I've started it is actually quite difficult to stop.

BTW, well spotted Dan, thanks for sharing!

You can play with the Maxi-BIAB calculator to work out how much you can do with your current equipment...

As far as I can tell, the limiting factor is basically what liquor:grain ratio you can get. We haven't determined an effective limit yet, but I'm assuming 2.5:1 (L:KG) would be impractical. 3:1 seems to work okay, but efficiency is reduced

The next limit is then how much wort you can get out of your boil, and that is simply your kettle - trub - end-of-boil headspace.

Hi tbeahrs,
many thanks for the feedback and that's also a very good question!
With the limited mash tun volume, it isn't just a case of add more grain and everything else stays the same, if you add more grain for the same volume of strike water eventually something has to give and that's head- space, i.e. an overflowing mash! However, we could reduce the strike water volume and increase the grain mass, this indeed can be done, but as you've noted, efficiency goes down the gurgler. There's a few reasons for this, the good thing is the answer lies partly in just simple mathematics (presuming all else is equal). Reduced volume of water = less working fluid to mobilise the sugars, and when a higher proportion of the original strike water volume remains stuck to the grain (i.e. same amount per kg of grain but lesser amount to begin with = higher proportion), efficiency suffers. There is a minimum proportion of liquor which is never drained from wet grain, more grain equates to more liquor retained, and when that medium for carrying away dissolved sugars get eaten in to, efficiency suffers. Sure, the concentration of dissolved sugars can increase, there could be some beneficial aspects (for efficiency) when it comes to the actual mash dynamics, but not enough to offset those proportional losses, hence overall efficiency is reduced.
This are a few reasons why sparging becomes a handy tool for stove top brewers. Firstly, bearing in mind that Maxi-BIAB uses a more conventional L:G ratio for mashing of around 3-4 L/kg, it frees up those sugars which would otherwise be lost from the process, and does so in a way which is not unfamiliar to brewing, i.e. a simple rinse step. Secondly, it takes advantage of the kettle volume which would otherwise be 'wasted', and as long as your heat source can manage it, I say use it!
When it comes to the actual numbers, IIRC, 5.5kg is the most I've ever mashed in a 19L stockpot, but my usual grainbill is about 4.5kg. This often yields about 23-25L of 1.050-1.055 in the fermenter, although I often supplement this with 5% of the grainbill as sugar, but that is indeed to style. This 4.5kg grainbill seems to be where efficiency is peaking, very seldom do I even have to do the numbers to work out what might have gone wrong. However, it seems 6kg can be managed without too much hassle or bother.
FWIW, some rough sums I did a while back indicated that up to 6kg the relative efficiency loss was tending towards 3% per kg of grain over 4kg, there's a chart below (the 6kg data is not my own, so YMMV). Beyond that, I suspect it will drop considerably, its something I've been meaning to test.
Hope this helps!