Mash Caps... Let me see what you got!

[skunkape]

I respect your skills. I'm not here for proving or disproving anything to anybody. I'm just a homebrewer, not an expert and hopefully not a d-bag.

TBH, I'm here mostly for recipes and memes.

 

[Bassman2003]

Cool. Low oxygen is not for everybody and is not essential for all brewers. It creates very clean beers without oxidation as a large flavor component. That might take away some perceived flavors in normal homebrew. But it also clears the way for other flavors to shine.

 

[DonT]

I respect your skills. I'm not here for proving or disproving anything to anybody. I'm just a homebrewer, not an expert and hopefully not a d-bag.

TBH, I'm here mostly for recipes and memes.

nevermind... me being dumb

 

[ethan44]

@DonT any update on if yours floats or not? I'm looking at a similar set up. Thanks.

 

[Bobby_M]

Didn't need a mashcap on this one.

 

[DonT]

@DonT any update on if yours floats or not? I'm looking at a similar set up. Thanks.

It doesn't need to float necessarily, it just needs to seal out air.
The lid I posted... I added the seal Bobby linked to and now it's a bit too tight to slide easily onto the pot. So I'm doing something slightly different. I found a place that would cut a circle of SS to a particular diameter, so with some careful measuring, I ordered it and it's coming Friday. I'm going to mount that wiper seal and it should side into the pot nicely. This piece is flat as opposed to the lid that is concave, which could trap air. My solution to that would be to drill a hole near the top of the curve and use a plug to let the air out. I'll probably do that anyway just to give me an easy way to take gravity samples. I'll post new pics when I get it all together.

 

[DuncB]

If you turn the lid over it won't have this issue.
"This piece is flat as opposed to the lid that is concave, which could trap air"

 

[Bilsch]

It doesn't need to float necessarily, it just needs to seal out air.
The lid I posted... I added the seal Bobby linked to and now it's a bit too tight to slide easily onto the pot. So I'm doing something slightly different. I found a place that would cut a circle of SS to a particular diameter, so with some careful measuring, I ordered it and it's coming Friday. I'm going to mount that wiper seal and it should side into the pot nicely. This piece is flat as opposed to the lid that is concave, which could trap air. My solution to that would be to drill a hole near the top of the curve and use a plug to let the air out. I'll probably do that anyway just to give me an easy way to take gravity samples. I'll post new pics when I get it all together.

Mashcaps really do need to float freely with full contact to the surface of the liquid and not drag along the vessel wall. Doing what you describe is not helping reduce oxygen exposure in the least. You are not only sealing out air but also sealing it in. The result is a wash. Also consider the oxygen contained in only a couple cubic inches of air is quite enough to oxidize the entire mash.

 

[JohnDBrewer]

I always use a lid on my mash, but I always did it for temperature control. Who knew?

 

[DonT]

Mashcaps really do need to float freely with full contact to the surface of the liquid and not drag along the vessel wall. Doing what you describe is not helping reduce oxygen exposure in the least. You are not only sealing out air but also sealing it in. The result is a wash. Also consider the oxygen contained in only a couple cubic inches of air is quite enough to oxidize the entire mash.

Show me what you came up with....

 

[Bassman2003]

Don, just take the lid you have and bend up the lip so you create a wall to allow it to float. It does have to float otherwise it is either under water so to speak or there will be air underneath if it is too high. Floating allows the cap to always be in contact with the surface.

 

[DonT]

I'm abandoning the lid.
I sourced a flat disc of the appropriate diameter so as long as you push it down on to the wort and have a way for the air to escape, it doesn't technically need to float.

 

[AlexKay]

Also consider the oxygen contained in only a couple cubic inches of air is quite enough to oxidize the entire mash.

I thought I’d run some numbers on this statement:

1. 100 mL is about 6 cubic inches.
2. 100 mL is roughly 5 millimoles of gas at ambient temperature and pressure, so for air, one millimole of oxygen.
3. Assume every oxygen molecule in that headspace goes into solution over the course of the mash, and reacts to form an off-flavor compound, X.
4. Assume X is a small molecule with a molar mass of ~100 g. This means there is 100 mg of X created by oxidation.
5. For a 20 L batch, that’s 5 mg of X per liter, or 5 ppm.

This is interesting to me because 5 ppm implies a bit about the identity of X. There are plenty of compounds that have far lower flavor thresholds (e.g., MBT, geosmin, 4VG), but there are also plenty that don’t (e.g., acetaldehyde, ethyl acetate.)

Also, in my judgment,(3) is likely a very poor assumption. Not every oxygen molecule will make a molecule of X, as there will be other things in the mash to react with. (An alternate way to say it is that collectively, all of the oxidation products must have a weighted average taste threshold of 5 ppm.)

 

[Bassman2003]

It is very complex. Those of use chasing it are still learning and trying things. The bottom line is that a small amount of O2 has an effect. Not just flavor but color, staling and shelf stability etc... Trapped air is pretty much finite but open air is constantly being replenished. So it is tough to quantify.

But there are limits on the other side too. Too little to zero oxygen has its own character as a lot of flavor components are related to oxidation or what is often referred to as micro oxidation. A tiny amount (scientific term) is needed for flavor. But this is all relative. Large breweries have a lot more liquid compared to surface area (square-cube law). So their brewhouses are more forgiving from an oxygen uptake point of view. Our homebrew systems are way more of a challenge with so much surface area compared to liquid. This is why so much flak has been given to the low oxygen crowd. One has to be over the top to reach the very low threshold. Under 2 ppm for the entire brew day (milling to pitching) would be a goal. Once it can be controlled then one can add or subtract to taste. Say go low for a pils and maybe a little higher for a Scottish ale etc...

It is a given in large breweries just like hydrostatic pressure in big CCVs. That 'large brewery taste' is because of these two things being inherent in their brewing setups. If one wants to emulate that output then limit the O2 and crank up the pressure on your fermenter and that is the best we can do as homebrewers.

 

[mabrungard]

The purpose of a mash cap is to reduce the liquid and mash surface area that is exposed to the ambient atmosphere. Having a sealed dead space above the mash isn't the same since there is a quantity of oxygen in that trapped air...unless you completely flushed that volume with an inert gas. That quantity of oxygen would have the opportunity to diffuse into the wort and oxidize it.

Placing an impervious barrier on the surface of the mash is a better method.

 

[DonT]

Placing an impervious barrier on the surface of the mash is a better method.

Which is what I've been talking about the whole time....

 

[Bilsch]

Show me what you came up with....

I have the same brand cap as you show in your pictures. I have reworked the lip so that it makes it taller and more buoyant. Just works out with my kettle to have about ~1/16" all the way round so the cap wont drag and can easily follow the volume fluctuations due to temperature change, adding removing water etc.

 

[Bilsch]

I thought I’d run some numbers on this statement:

1. 100 mL is about 6 cubic inches.
2. 100 mL is roughly 5 millimoles of gas at ambient temperature and pressure, so for air, one millimole of oxygen.
3. Assume every oxygen molecule in that headspace goes into solution over the course of the mash, and reacts to form an off-flavor compound, X.
4. Assume X is a small molecule with a molar mass of ~100 g. This means there is 100 mg of X created by oxidation.
5. For a 20 L batch, that’s 5 mg of X per liter, or 5 ppm.

This is interesting to me because 5 ppm implies a bit about the identity of X. There are plenty of compounds that have far lower flavor thresholds (e.g., MBT, geosmin, 4VG), but there are also plenty that don’t (e.g., acetaldehyde, ethyl acetate.)

Also, in my judgment,(3) is likely a very poor assumption. Not every oxygen molecule will make a molecule of X, as there will be other things in the mash to react with. (An alternate way to say it is that collectively, all of the oxidation products must have a weighted average taste threshold of 5 ppm.)

On the cold side larger breweries are concerned with parts per billion of oxygen during handling after fermentation and package filling. Same malt flavor compounds being oxidized.

In the Lodo world those with in-process oxygen sensors get concerned when we see anything other then 0.0 ppm on the transmitter screen. By the time it gets to 1ppm I'm pretty upset and trying to figure out where things went wrong. Some are even using traces probes so they can see PPB resolution.

 

[McMullan]

Also consider the oxygen contained in only a couple cubic inches of air is quite enough to oxidize the entire mash.

The grist, being organic, has an inherent oxidative load far greater than the air-liquid interface. Does using a ‘mash cap’ really make a discernible difference? I accept there are quality benefits to be gained from limiting O2 exposure throughout the process, but I’m a bit skeptical about mash caps. And, to be honest, I’m a bit concerned about the materials some brewers might be throwing on top of what is a hot acidic liquid for an hour or two.

 

[Brooothru]

Show me what you came up with....

I use a Braumeister AIO with a 'factory' LoDO mash cap. The first picture shows the malt pipe in place with the top plate and screen in place. Recirculation is a bottom up flow pattern through the malt bed. When the mash begins, the entire malt pipe in submerged in strike water with about ½" liquid above the top of the screen.

The second pic shows the beveled edge mash cap in place, floating above the malt pipe on the upward flowing wort. The flow of wort is very gentle without any splashing and suppresses "fountaining" if any channeling were to occur in the malt bed. The only liquid/atmospheric interface contact is reduced significantly to less than ½" gap around the radius of the cap. It is 304 stainless steel, as is the entire kettle surface and all the assembled pieces that come in contact with the mash and boiling wort, including chill and transfer to a stainless fermentation tank, and eventually a stainless keg.

 

[Bassman2003]

After using one of these for 3-4 years now, I do not see any reason to stop. Outside of the O2 benefits, It helps to keep temps stable and returning the recirc flow under the water instead of sprinkling on top of the liquid just makes more logical sense to me. Why purposefully aerate if one does not have to? Just dogmatic imho.

 

[Brooothru]

After using one of these for 3-4 years now, I do not see any reason to stop. Outside of the O2 benefits, It helps to keep temps stable and returning the recirc flow under the water instead of sprinkling on top of the liquid just makes more logical sense to me. Why purposefully aerate if one does not have to? Just dogmatic imho.

That's my approach to LoDO (please, don't judge me) brewing. Not a chest-beating acolyte. It just makes sense to me.

 

[beersk]

I use the lid from my original 5 gallon stock pot when I started brewing. It fits perfectly in a 10 gallon Igloo cooler. @Red over White Why even bother with yours? I looks like it covers only about 50-60% over your mash. Cover 100% or bust, I say.

 

[Red over White]

I use the lid from my original 5 gallon stock pot when I started brewing. It fits perfectly in a 10 gallon Igloo cooler. @Red over White Why even bother with yours? I looks like it covers only about 50-60% over your mash. Cover 100% or bust, I say.

View attachment 840623

I have 3 mashtuns, that cap pulls double duty for the AIO & 8 gal HLT, but it is stored in my direct fired 16 gal mashtun where I took the picture. I have a 3v gas system and an indoor 3v electric system. TBH, I can't wait to brew outside again on propane this spring when I can set everything up the night before.

 

[Brooothru]

I have 3 mashtuns, that cap pulls double duty for the AIO & 8 gal HLT, but it is stored in my direct fired 16 gal mashtun where I took the picture. I have a 3v gas system and an indoor 3v electric system. TBH, I can't wait to brew outside again on propane this spring when I can set everything up the night before.

You’re singin’ my song. I’m past ready for Spring to be here yesterday. I’ve still got two partial kegs in the kegerator and one more untapped in the beer fridge. BUT I WANT TO BREW!!!

Sick and tired of lookin’ out the window and seeing cold, dark skies. SWMBO’d says “No” to indoor brewing, so I’m S.O.L. until Winter breaks. Got 70~80# of grain in Vittle Vaults, a freezer full of hops, and a metric crap ton of yeast that’s ready to go. And at least two dozen recipes that I want to brew (but prolly never will) with the list growing daily ‘cause I waste my days hangin’ with my homies here on HBT rather than actually making beer!

Only the act of brewing will break the fever.

 

[Red over White]

You’re singin’ my song. I’m past ready for Spring to be here yesterday. I’ve still got two partial kegs in the kegerator and one more untapped in the beer fridge. BUT I WANT TO BREW!!!

Sick and tired of lookin’ out the window and seeing cold, dark skies. SWMBO’d says “No” to indoor brewing, so I’m S.O.L. until Winter breaks. Got 70~80# of grain in Vittle Vaults, a freezer full of hops, and a metric crap ton of yeast that’s ready to go. And at least two dozen recipes that I want to brew (but prolly never will) with the list growing daily ‘cause I waste my days hangin’ with my homies here on HBT rather than actually making beer!

Only the act of brewing will break the fever.

Yeah, I love the ground water temps in the winter, but I'd rather be brewing outside while grilling or smoking something. This weekend I will do another fest beer and put a maibock on that yeast cake asap. I've got 4 more weeks until I can be outside here in NC without lines nearly freezing overnight.

I feel ya, big winter beers don't get depleted as quickly and the brew days get further apart. I love setting aside a whole day to JUST brew and eat to much. Hopefully, that big rodent in PA sez you don't have 6 more weeks of winter!

 

[Brooothru]

Yeah, I love the ground water temps in the winter, but I'd rather be brewing outside while grilling or smoking something. This weekend I will do another fest beer and put a maibock on that yeast cake asap. I've got 4 more weeks until I can be outside here in NC without lines nearly freezing overnight.

I feel ya, big winter beers don't get depleted as quickly and the brew days get further apart. I love setting aside a whole day to JUST brew and eat to much. Hopefully, that big rodent in PA sez you don't have 6 more weeks of winter!

This winter hasn’t been that bad this year, but I’ve had enough. We’ll be heading down to Florida in a few weeks to thaw out with our grandkids there. By the time we get back it’ll be tax time, then hopefully the weather will warm enough to get brewing, regardless of what that overgrown rat in Punxsutawney does.

 

[Bassman2003]

Suck it up and get out there! Just kidding. I prefer a warm brew day as well but the show must go on. In Texas, I only get a few times a year when the chiller really works well.

 

[Brooothru]

Suck it up and get out there! Just kidding. I prefer a warm brew day as well but the show must go on. In Texas, I only get a few times a year when the chiller really works well.

Oh, I hear that. I spent three years in the late 70s south of San Antonio instructing Student Naval Aviators in the fine art of not killing one’s self in an airplane. I was mostly successful. One summer (1980 to be exact) it didn’t rain for over three months.

There was a stretch of 90 days when the temperature exceeded 90F, including 30 consecutive days when it was in excess of 100F. Often the overnight low temperature was still above 90F. Even with an air conditioned cockpit, it got mighty hot under a plexiglass bubble canopy.

It took Hurricane Allen to finally break the fever as well as the drought. Of course my wife was in a hospital in Corpus Christi 60 miles away with our newborn daughter when the storm came ashore at South Padre Island.

Certainly not weather conducive to brewing beer, or barbeque either. Sure do miss the flavor of mesquite done right, however.

 

[beersk]

I often miss my brewing outside days. I lived in a place with a garage for a while and I loved it, even in the winter. Just had to mash inside and carry the kettle outside/back inside for chilling. I remember brewing one day when it was 6F. That was fun. Could barely see the boil. That was a hoppy red I brewed way back in January of 2010. Loved it.
But now I brew inside and it's so much better. No bugs, no wind, limitless gas supply, it's all right there. I don't have to worry about anyone not liking the smell thankfully. I do often wish I had a garage so I could brew outside though...

 

[Bassman2003]

I have been brewing in the garage for 20+ years. It is fine but I would love a dedicated indoor space. Maybe some day but it seems indulgent just for a hobby.

 

[JAReeves]

You’re singin’ my song. I’m past ready for Spring to be here yesterday. I’ve still got two partial kegs in the kegerator and one more untapped in the beer fridge. BUT I WANT TO BREW!!!

Sick and tired of lookin’ out the window and seeing cold, dark skies. SWMBO’d says “No” to indoor brewing, so I’m S.O.L. until Winter breaks. Got 70~80# of grain in Vittle Vaults, a freezer full of hops, and a metric crap ton of yeast that’s ready to go. And at least two dozen recipes that I want to brew (but prolly never will) with the list growing daily ‘cause I waste my days hangin’ with my homies here on HBT rather than actually making beer!

Only the act of brewing will break the fever.

 

[Red over White]

Setting up for Saturday mornings 10 gal batch of festbier. This is my mash cap in the 17 gal brewzilla. It's a SS pizza pan with the exact hardware my other cap has underneath. It has a small gap not visible because of its shape, but it’s very effective and moves up and down freely.

 

[day_trippr]

Is there something under that cap to disperse the return so it isn't drilling straight down into the mash bed?

Cheers!

 

[Red over White]

Is there something under that cap to disperse the return so it isn't drilling straight down into the mash bed?

Cheers!

Yes, this is the underside. Fugly, but effective.

The SS wire and ring on my mash caps were robbed from SS colanders to deflect the flow off the bottom of the cap and to not to cause disturbance to the surface or the grain bed.

Boring ass explanation not asked for:

This was proved out initially with a stale mash after runoff. I just kept playing with it until I seen the desirable results. The return shouldn't create any turbulence around the cap, any interaction is inducing oxygen. If it's completely still with no undulations the only issue will be the CO² generated from dough-in and the ingress that is inherent with bubble xfer is that those CO² bubbles will cause on the surface. Bubbles on the surface of the mash create a much bigger surface area and thus a bigger area for oxygen ingress. That much reduced surface area can be easily tamped down with preemptive antioxidants though. If that sounds goofy, I can refine it hopefully better if need be.

 

[JohnDBrewer]

Anyone design a mash cap for a keggle? (Yes I still use a keggle.)

The problem is the top hole is 10-inches, and the keg is15-inches. My false bottom is hinged and folds. Would a silicone baking sheet float? They're pretty cheap on Amazon and I could cut one down, but not sure it would float. I use a RIMS, so wort is recirculating with just a tube lying on top of the mash. The cap would have to float on top of that. Thoughts?

 

[ba-brewer]

@Schlenkerla mash ball approach seems like it would work. He floated a bunch of small balls on the mash.

 

[Bassman2003]

Anyone design a mash cap for a keggle? (Yes I still use a keggle.)

The problem is the top hole is 10-inches, and the keg is15-inches. My false bottom is hinged and folds. Would a silicone baking sheet float? They're pretty cheap on Amazon and I could cut one down, but not sure it would float. I use a RIMS, so wort is recirculating with just a tube lying on top of the mash. The cap would have to float on top of that. Thoughts?

I think the silicon baking sheet might work if it is think enough to maintain buoyancy as one entity and actually stay on top of the liquid. You could possibly make a hole in the center to tun your recirc tubing through to let the silicon free float around it.