Unusual Mash Problem

[bobtheUKbrewer2]

Hello knowledgeable friends, I am a BIAB man, using an extended Burco boiler. I have used the same Maris Otter crushed grain, from the same source, for at least 20 years. The last 4 mashes all behaved as follows. About 30 minutes into the mash, I turn on the heater element at reduced power to increase the temperature by 2 to 3 degress C.
The liquid level rises so much I have to use two 4 litre jugs as recirculating overflows. My bag is a few years old and when I wash and rinse it, water is not retained by the bag. I have thought of a work round using a stainless steel breather tube up the inside wall of the boiler. Any thoughts ? Many thanks.

Bob (the UK brewer)

 

[hotbeer]

I can't imagine using recirculation with BIAB. I guess it can be done, but the bags I use are too tight a mesh to allow for that.

If you successfully did this before, then what's different? Might be the old bag, but I wouldn't really think so. Finer crush or different fermentable malts and grains in the mash might be the culprit.

 

[Bassman2003]

Does it only happen after you turn the heat on? Or just 30 min. into the mash?

It is acting like a stuck mash. The recirc flow is getting clogged up somewhere, probably going through the grain bed and the pump is sucking the remaining liquid under the bag and putting on top of the kettle. Hence the overflow.

If your recipe and grain has remained constant, can you think of anything else that has changed to create the stuck mash? The bag should not be an issue as they only get looser as they age.

 

[bobtheUKbrewer2]

difficult to describe and I hace confused you. by recirc I mean running out of the tap. No pump. Only maris otter and crystal malt. Only when heat turned on. It might be a finer crush, I buy another 25 kilo bag tomorrow so next brew may throw some light on it. thanks

 

[Bassman2003]

Ok. Please explain a little more. Are you running wort out of your valve into a container and then pouring it back in to the mash?

 

[bobtheUKbrewer2]

yes, but only to prevent overflow - I estimate 5 litres of expansion. A 4 litre jug is not sufficient.

 

[Bassman2003]

Please explain more as a mash just sitting there will not overflow by itself. The whole process is needed to see what you are doing.

 

[bobtheUKbrewer2]

The mash starts at 68 deg C - after 30 minutes it is 66.5, so I turn on the heat and in about 5 minutes the level rises approx 5 litres - near to overflow so I fill two 4 litre jugs from the tap, pouring one back in, refill that jug and then pour in second jug - I am using the jugs as overflow reservoirs. Not because I want to . Very vigorous agitation with my large paddle releases some (gas) between the outside of the bag and the inside of the Burco.

 

[Bassman2003]

Thanks. I have no idea why turning on the heat would cause the level of the mash/wort to go higher. Is the mash sitting there still? No recirc or wort moving? Things expand when they get close to boiling but not with only a few degrees during a mash. Are you sure the temperature change is only 2-3 degrees C?

 

[bobtheUKbrewer2]

obviously right above the Burco heating element it is close to 100 degrees C, my technique is to run off wort from the bottom tap and tip it in the top, thus stopping excessive temperature in the wort. It can't be a steam problem bacause steam condenses immediately unless the wort is boiling - it isn't.

 

[Bassman2003]

Hopefully someone else will chime in as I am kind of stumped other than the temps being a lot hotter than expected.

 

[bobtheUKbrewer2]

any electric mash heater will create high local temps, so I am taking wort at 70 deg C out the bottom and adding it back in at the top - many thanks Bassman - I like draught Bass...........

 

[hotbeer]

If that thing isn't insulated well then wrap it with some large fluffy bath towels or other insulation. Might be you could use a well insulated ice chest of cooler for your mash and not have to use any extra heating at all if you get your strike temp correct.

I'm still having trouble why you have to fill a container and pour another back in. Is this thing not big enough for your batch size?

As you said, maybe someone more familiar with your procedures will chime in. At the moment your process doesn't seem to be what most of us do. But I can be pretty dense sometimes and might have that aha moment a little while later.

 

[bobtheUKbrewer2]

ok, un til 2 months ago I mashed normally. Then this phenomenon started. The liquid level rose to the point where I had to take mitigatory actions ie temporarily put some wort into jugs, continually drawing off and topping up. The grain is in the bag, pressing against the inside of the boiler, and not letting "air" vent, so the level rises. I do not know the mechanism. Next brew there will be a blow off tube. Stay tuned. Very difficult to describe, understand some of you didn't understand. My fault. If it continues I will video it.

 

[doug293cz]

There is no way thermal expansion can account for the "extra" volume of wort. Wort only expands ~4% going from room temp to boiling. From mash temp to boiling is only about 2% expansion. In a 40 qt mash, that would only be 0.8 qt max accounted for by expansion.

Since OP is manually vorlaufing during mash heating, it seems likely that the "extra" volume is due to the bag not draining into the dead space under the bag at rate high enough to make up for the rate at which the wort is drained for the vorlauf.

Brew on

 

[Bassman2003]

Without a recirculation going, I do not see the need/cause for draining of wort? If there was deadspace under the bag, the bag must be made out of plastic! Once you add the strike water and grain with a stir, there would be zero air in the vessel. The only mechanism for the wort to "grow" is heat expansion and Doug pointed out how small this would be.

So what is the part of your process that we are missing?

 

[bobtheUKbrewer2]

Until 4 brews ago, I filled the Burco with 33 litres of water, and added around 9 lb crushed pale malt and 1.5 lb of crystal malt. Maybe twice in the 60 minute mash I turned on the heater at the bottom of the Burco to maintain mash temperature. The liquid level did not change at all. Now when heater on it rises significantly to the extent that I have to run some wort into overflow jugs. It must be a finer crush on the pale malt, but I struggle to understand the mechanism.

Bassman, I accept that water expansion is tiny. I believe after further thought that a pocket of steam is forming under the bag and thus displacing liquid, which can only rise in the mash vessel. My next brew will have a vent tube, as mentioned earlier, and I will try to monitor the temperature in the vent.

To all, I am not deliberately re-circulating wort, I am preventing overflow.

Thanks to all.

 

[RM-MN]

Until 4 brews ago, I filled the Burco with 33 litres of water, and added around 9 lb crushed pale malt and 1.5 lb of crystal malt. Maybe twice in the 60 minute mash I turned on the heater at the bottom of the Burco to maintain mash temperature. The liquid level did not change at all. Now when heater on it rises significantly to the extent that I have to run some wort into overflow jugs. It must be a finer crush on the pale malt, but I struggle to understand the mechanism.

Bassman, I accept that water expansion is tiny. I believe after further thought that a pocket of steam is forming under the bag and thus displacing liquid, which can only rise in the mash vessel. My next brew will have a vent tube, as mentioned earlier, and I will try to monitor the temperature in the vent.

To all, I am not deliberately re-circulating wort, I am preventing overflow.

Thanks to all.

A better idea is to leave the heater turned off. Unless you are constantly and vigorously stirring while heating you will have a temperature differential with the bottom being above the temperature that denatures the enzymes needed for coversion. If the falling temperature bothers you a lot, insulate the mash. However, it is likely that by the time 20 minutes have passed that nearly all the conversion is complete and your heating has no affect on conversion. With finely crushed malt, conversion happens very quickly.

 

[DuncB]

Burco is a very binary device.
It heats at full power or nothing. I reckon you are bringing small volume of wort to the boil hence expansion.

 

[madscientist451]

I stopped checking temps and fussing with my BIAB brews a few years back and the beer comes out fine. I put a layer of aluminum foil right on top of the mash, put the lid on and then wrap up the kettle in an old coat. My stove has the smooth glass top and that retains some heat. I only loose a few degrees F over an hour. Maybe that will work for you.

 

[Bassman2003]

I think I do not know what a Burco is. I am envisioning a kettle with a propane gas burner underneath on the outside of the kettle. Is it something different?

 

[bobtheUKbrewer2]

Bassman - it is a tea urn - kettle element mounted in the base not in contact with water

DuncB = the heater element is controlled by a TRIAC circuit so fully adjustable

RM-MN - during heating I am running off water from the tap and pouring it into the top of the mash, to prevent excessive temperature above the element. This was always my technique. Only the last 4 brews have had the overflow problem. Will report back on next mash with a vent between bag and inside of Burco.

 

[Bassman2003]

Thanks. I do not understand how anything would be between the bottom of the bag and the bottom of the pot? The wort would be everywhere - "underwater".

 

[bobtheUKbrewer2]

Bassman - I too am baffled - it must be steam.....

 

[hotbeer]

Maybe you should change up your procedures and desires to suit the equipment you are using.

Recirculating as you are doing it during the time you are doing your mash rest is resulting in your mash temps going down too much and you having to run the heat so often. Steam is hot, so at least a part of your mash is likely getting way too hot.

If you want to Vorlauf, then wait till the mash rest is over. During the rest, wrap that boiler with fluffy bath towels or other insulation. If you heat to a mash out temp after the rest, then you can have all the time in the world to wait for your wort to drain and give you a clean wort.

Though I and others have found no value in putting clean wort in the boil kettle or FV for the type beers we generally make.

 

[Broken Crow]

Just wondering... You mention buying another 25 kilo bag... presumably you mill it yourself and that hasn't changed, but I'm wondering if the problem started with a new bag and maybe something in the grain has changed causing it to produce more 'flour' and plug up your bag? I know that here in Canada, our bakers had a problem recently attributed to climate problems with a years crop, making substandard flour that produced lower-rising breads. Could the grain have changed?

 

[bobtheUKbrewer2]

Broken Crow, I buy the pale malt in crushed form. But I and others on here cannot explain why a finer milled grain would "trap" "gas" and cause substantial volume increase of around 5 litres....

I normally add the grain when water is 70 C, causing temperature to drop to 63-64 so I will also turn the power on "gently" while mashing in.....I will report on the new grain purchase and the next brew in due course.......

 

[dtashmore547]

in the early 80's I also used a Burco boiler but had a different approach, I mounted a windscreen wiper motor on the centre of the lid with a bar under the lid where I suspended my bag, I had lots of space around my bag for it to rotate and I controlled the temperature with a probe and solid state relay controller. from what you describe, there it's probably not enough space around your grain bag for the water to pass from the top down to the bottom easily so your wort gathers on the top you probably need to make some sort of passage bypassing your bag to get the wort past the bag to enable flow top to bottom.

 

[Bassman2003]

Do you have any kind of false bottom to elevate the bag?

 

[wsmith1625]

Your bag is getting clogged. You're expecting the wort levels in the boiler and bag to equalize, but you're filling the bag faster than it can return the wort to the boiler. I would clean the bag well with a good soak in hot water and PBW. Then I would check the grain crush. Also, adjuncts like corn and rice can cause drainage problems.

 

[bobtheUKbrewer2]

wsmith - I am not filling the bag at all. I am removing liquid to avoid overflow, but obviously I need to return this liquid, it is recirculating, butI do not wish to do it, and up to 4 brews ago I did not do it.

Bassman - no the borrom of th bag is 4 inches above the Burco bottom

dtashmore - the bag is bigger than th burco boiler, both in terms of length and diameter

 

[wsmith1625]

Have you tried stirring as you heat the mash? What's your water to grain ratio? I don't think you shared the size and model of your water boiler either. That would be helpful.

 

[SanPancho]

Have you asked your source for grains if they’ve recently changed their mill or mill settings? If the grist is too fine for flow, it will also block flow to the vast majority of the bag’s surface area. That means overflow.

 

[bobtheUKbrewer2]

I repeat that for many years I have used the same technique with no problems.

Wsmith, as purchased a Burco boiler holds 23 litres. Mine has been modified by welding on the top of another Burco boiler so that it holds 42 litres. I start with 33 litres of water and 10.5 lb of grain, ie a full volume mash.

San Pancho - since I start with maybe 6 inches of liquid above the grain, and as part of the initial heating cycle to reach approx 68, and as I run off liquid from the bottom tap to avoid excessive local heating just above the heating element, I believe you have diagnosed the issue. If the grain is too finely milled it will not allow liquid to flow through it - because - the diameter of the bag is greater than the diameter of the boiler.

I am purchasing a new 25 kg bag of crushed pale malt in a few days so will report if same issue occurs. If it does, I have already made a stainless steel vent that will be positioned between the bag and the inside of the bouler.

Sincere thanks to all contributors to this thread.

 

[micraftbeer]

I agree with some of the posts above. Your hot wort/steam/etc is trying to rise to the top and it gets trapped, giving you the overflow phenomenna. Maybe finer crush, maybe tired old bag that doesn't like to let stuff through.

Vent pipe outside the bag, new bag, not as fine of a crush, stirring of the whole mash when your burner is on to mechanical make an escape path for the heat, etc.