Stuck mash

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bitter_dave
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Re: Stuck mash

Post by bitter_dave » Mon Oct 08, 2018 8:50 am

guypettigrew wrote:
Mon Oct 08, 2018 8:26 am

Ah, the old 'Dave Line' approach! My very first mashes many decades ago were done in a double bucket system. Never really got on well with it. The inner bucket always got jammed inside the outer one. Then I moved onto a canvas bag with a mesh bottom. Can't for the life of me remember how I supported the mesh. But I do remember wrapping the bucket round with two layers of hot water tank insulation material. Then I moved on to the faithful cooler box with a slotted 'D' manifold.

The only stuck mashes I ever had were with the double bucket. I think I drilled the holes too large and some grain got through and blocked the tap. Can't really remember, though. It was way back in the late '70s!

None of this is any help to you, I know! Just a chance for me to reminisce.

Looking at your recent posts I see you top up the mash with water before running the wort off. Have you tried running the wort off at the end of the mash time before topping up with water? I'm just wondering if adding more water is stirring things up and causing it to clog before a proper filter bed of grain has formed on top of your false bottom.

I've never batch sparged, by the way, so probably don't know what I'm talking about!

Guy
I got the idea from Wheeler and as I recall it used to work ok although there was a fair of dead space. If I did this it would be in the mash tun; not sure I will be able to find a bin exactly the right size but will look into it.

Alternative is braid.

I have tried running off before toppong up. Did not not completely stick if I recall but v slow indeed

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Re: Stuck mash

Post by chefgage » Mon Oct 08, 2018 8:57 am

Did you try as jocky said about making sure there is water in the silicon tube before mashing in?

I only ask as i seem to remember a similar issue when i had my 3 vessel setup. What i woukd do is fill the mash tun with the required amount of water. Then slowly open the drain valve untill water comes out. Then shut the valve. Then mash in as normal. If i did not hardly wort would come out. This was due to an air lock i believe.

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Trefoyl
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Re: Stuck mash

Post by Trefoyl » Mon Oct 08, 2018 11:47 am

bitter_dave wrote:
Sun Oct 07, 2018 8:36 am
dbambrick996 wrote:
Sat Oct 06, 2018 11:09 pm
If you are milling your own grain check the crush , also get some oat husks it will help

I have a similar setup and was getting stuck mash as my crush size was too fine for my system. I now find that a crush if 1.1mm works good for me
Thanks for the suggestion. I get my grain pre-crushed so I don’t think that’s a solution.
I have the same set up in a cooler and was getting stuck mashes until I made the crush more course. Interestingly I did not lose efficiency. I don’t have proper feeler gauges to measure the gap. I used to have some years ago when I set my own points in the car, but must have lost them.
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Re: Stuck mash

Post by lord groan » Mon Oct 08, 2018 8:35 pm

I wonder... looking at your false bottom, it is very slightly dished in shape and if I'm looking at the pics right your wort pick up tube collects the wort from under the dish (concave side) ..yes?
If so I'd guess the weight of grain sitting on the false bottom is pressing down on the convex upper side of the fb, it wouldn't have to press much before the open collector side of the elbow under the mesh squashes flat on the bottom of the mash tun, effectively sealing the open end of the elbow flat on the bottom, hence no flow and a stuck mash.
The moment you take the grain out the dish flexes back up from the bottom and the problem vanishes. Perhaps you could test by filling the mt with mash temperature water and putting something heavy on the fb, a housebrick would probably serve to demonstrate, with no grain you'd have a fairly clear view and be able to see if the FB does squash down.
Worth a try? If it is this you could easily fix the problem by getting a couple of short SS bolts and screwing them through from the underside next to the pick up tube until the heads are just slightly higher than the tube, then when the fb gets squashed down the bolt heads will hit the bottom of the mt first and prevent it from pressing the pick up tube against the bottom
hth

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Trefoyl
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Re: Stuck mash

Post by Trefoyl » Mon Oct 08, 2018 8:57 pm

There does seem to be a lot of space around the false bottom. Mine goes up to the edges
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Kev888
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Re: Stuck mash

Post by Kev888 » Tue Oct 09, 2018 10:55 am

Between the weight of the grain and suction (especially once things begin sticking) the force between false bottom and MT base can be quite high; I've had thick false bottoms and stainless mash tun bases deformed by this in the past. You could perhaps try putting something between the false bottom and MT base that would physically prevent the outlet being pushed against the floor, and/or fix something under the outlet that would stop it making a seal if it was.

Another thing people have reported sometimes are flexible tubes kinking (rather than collapsing as such) as things move about, which can happen with more space around the edges of the bottom. But your rigid sleeve would likely have stopped that if it had been occurring.

Otherwise I can't see why it shouldn't work (theres nothing very strange about it), unless there are more generic causes. Like not starting the run-off slowly enough to begin with, or building up to too fast a rate. False bottoms are very even and uniform, but it means if the grain bed does over-compact then it does so uniformly across the bottom, leaving few paths for the wort to get through.

An unsuitable crush can make things worse, but unless there is an excessive amount of flour then pre-crushed grains from the usual suppliers are typically not over-fine and work with most perforated false bottoms. What is the hole/perforation size and where was the grain crushed?
Kev

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Re: Stuck mash

Post by peteturbo » Sun Oct 14, 2018 2:07 pm

I am jealous of all your expensive set ups. i use plumbing braid and a mesh tube. i like to have a decent space for the liquid to collect in so i have a simple aquarium plastic filter cut to shape and support it with aquarium filter balls (about 1.5 inch diam). this protects the strainer pipes from the weight and creates a deep well under the false floor.
this worked ok, but got quite a lot of bypass, so bought a cheap homebrew bag thing and used this as well.
plus a more adjustable tap (about two quid).
i think that suspending and supporting the floor is important. expect bypass, so ensure the small bypass can flush through. it will settle sooner or later.
I NEVER stir the bottom and limit top stirring.
My mash is thick - 5kg for 15L.
My kettle sits above the mash tun. once the starch is gone (iodine test), i get the outflow going slow and steady then continuously sparge by simply matching kettle tap into the top to outflow. gently mix the top inch with a spoon.
no more sticking!

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Re: Stuck mash

Post by HTH1975 » Sun Oct 14, 2018 4:35 pm

5kg in 15L isn’t particularly a thick mash - that is 3L/kg, which is at the thinner end of the scale.

2.5L/kg is pretty standard, giving 12.5L with 5kg of grain.

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Re: Stuck mash

Post by Jocky » Mon Oct 15, 2018 4:30 pm

Well I have no idea then. I know another chap that is having a very similar problem to you with the same false bottom and silicon tubing, so there's obviously something not quite right here. In his case he opens the valve, a short dribble of wort comes out and then nothing. He's had some more success by flooding the tube with water before adding grain.

I used the same FB but with a bottom drain underneath it for 30 batches, so that's why I'm puzzled by this - it must be to do with the way it's connected. I still think it's the silicon tube. It just seems to easy for a tube that you can pinch closed with your hand to get squashed closed by several kilos of hot water and malt.
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Re: Stuck mash

Post by bitter_dave » Tue Oct 16, 2018 10:00 pm

Thanks for all your suggestions; I appreciate all the help you’ve given me everyone.

For my next beer I’m going to try something different. I’ve found a fermenting bin that fits into the mash tun. I’ve therefore drilled 2.5 mm holes in the bottom spaced 1cm apart to make a a kind of filter basket thing. The bin rests on the old connector for the false bottom so should get flow ok. Will see how that goes.
0EC9D587-B0D7-4941-B944-24AC1D346DA2.jpeg

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Re: Stuck mash

Post by bitter_dave » Tue Oct 16, 2018 10:05 pm

chefgage wrote:
Mon Oct 08, 2018 8:57 am
Did you try as jocky said about making sure there is water in the silicon tube before mashing in?

I only ask as i seem to remember a similar issue when i had my 3 vessel setup. What i woukd do is fill the mash tun with the required amount of water. Then slowly open the drain valve untill water comes out. Then shut the valve. Then mash in as normal. If i did not hardly wort would come out. This was due to an air lock i believe.
I forgot to do this, although something tells me it’s not that simple. If I have another go with the false bottom i’ll sure I do it. Thanks for the comment :)

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bitter_dave
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Re: Stuck mash

Post by bitter_dave » Tue Oct 16, 2018 10:09 pm

Trefoyl wrote:
Mon Oct 08, 2018 11:47 am
bitter_dave wrote:
Sun Oct 07, 2018 8:36 am
dbambrick996 wrote:
Sat Oct 06, 2018 11:09 pm
If you are milling your own grain check the crush , also get some oat husks it will help

I have a similar setup and was getting stuck mash as my crush size was too fine for my system. I now find that a crush if 1.1mm works good for me
Thanks for the suggestion. I get my grain pre-crushed so I don’t think that’s a solution.
I have the same set up in a cooler and was getting stuck mashes until I made the crush more course. Interestingly I did not lose efficiency. I don’t have proper feeler gauges to measure the gap. I used to have some years ago when I set my own points in the car, but must have lost them.
Thanks Trefoyl. Maybe the crush contributed. I don’t really want to get involved in crushing my own grain though

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bitter_dave
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Re: Stuck mash

Post by bitter_dave » Tue Oct 16, 2018 10:12 pm

Trefoyl wrote:
Mon Oct 08, 2018 8:57 pm
There does seem to be a lot of space around the false bottom. Mine goes up to the edges
Good point. Maybe the small size of the false bottom was making it unsteady

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Re: Stuck mash

Post by Trefoyl » Wed Oct 17, 2018 11:54 am

I took a picture of the crush, it is is quite coarse.
Image
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Re: Stuck mash

Post by bitter_dave » Sun Nov 04, 2018 10:20 pm

Hurray! Brewed today with false bottom and no stuck mash! Made a simple pale malt-only brew using cascade hops (about 1038) (liberty bell yeas yeast). I put tubing around the edge of the false bottom, used the short piece of copper tube to cover the tubing leading from the bottom to the tap, and made sure there was water in the tubing before I mashed in to avoid air pockets or collapsed tubing. I used a second paddle to hold the false bottom in place whist stirring the mash, although not sure this was necessary. In any case it worked a charm.

Anyway, thank you for all your help everyone :)
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