Increasing mash efficiency

Mashing
1

I’ve been getting about 75% efficiency with my single infusion, batch sparge mashes, but I suspect I might be able to do better. My water source is relatively soft and, when I plug the numbers into John Palmer’s nomograph on the back cover of “How to Brew”, it appears that my mash pH is around 5.8, suggesting my water source is most appropriate for amber colored beers.

I’m thinking about a couple of ways to lower the mash pH and make it more appropriate for the lighter style Belgian beers I brew (tripels, strong goldens, saisons, BPAs, etc). One would be doing an acid rest and the other approach would be adding acidulated malt.

I’ve heard that an acid rest may help to create acids by activating phytase, but that this takes quite a length of time to happen (hours?). A staff person at a homebrew supply store told me he does this (he uses the same water source and mash process as me) and his mash efficiencies are regularly in the mid 80s. I’m dubious and not too excited about trying to get the temperature right by adding more hot water to get the temp to mash temps since I’ve found the calculators don’t always work very well with water additions.

I’m frankly more interested in adding acidulated malt, but am unsure of how much I’d need to add – Palmer talks about up to 10%. I thought I’d start with 1% of my grain weight and add more in each batch to see what effect it has in mash efficiency.

Maybe I’m already fine with 75%, but if it’s just a simple matter of a few ounces of acid malt for better efficiency (perhaps even better taste), I’d say that’s great.

The third option is going to take me a little longer to understand – adjusting water chemistry. According to my initial attempts with online calculators, it would likely be a matter of a couple of grams of gypsum and calcium chloride. While that doesn’t sound like a lot, my guess is that it could actually be quite a bit of mineral to add and I’m not sure I want to waste a batch trying until I get a sense of proportion.

Any suggestions?

As usual, thanks for any and all help.

2

[quote=“Antwerp”]I’ve been getting about 75% efficiency with my single infusion, batch sparge mashes, but I suspect I might be able to do better. My water source is relatively soft and, when I plug the numbers into John Palmer’s nomograph on the back cover of “How to Brew”, it appears that my mash pH is around 5.8, suggesting my water source is most appropriate for amber colored beers.

I’m thinking about a couple of ways to lower the mash pH and make it more appropriate for the lighter style Belgian beers I brew (tripels, strong goldens, saisons, BPAs, etc). One would be doing an acid rest and the other approach would be adding acidulated malt.

I’ve heard that an acid rest may help to create acids by activating phytase, but that this takes quite a length of time to happen (hours?). A staff person at a homebrew supply store told me he does this (he uses the same water source and mash process as me) and his mash efficiencies are regularly in the mid 80s. I’m dubious and not too excited about trying to get the temperature right by adding more hot water to get the temp to mash temps since I’ve found the calculators don’t always work very well with water additions.

I’m frankly more interested in adding acidulated malt, but am unsure of how much I’d need to add – Palmer talks about up to 10%. I thought I’d start with 1% of my grain weight and add more in each batch to see what effect it has in mash efficiency.

Maybe I’m already fine with 75%, but if it’s just a simple matter of a few ounces of acid malt for better efficiency (perhaps even better taste), I’d say that’s great.

The third option is going to take me a little longer to understand – adjusting water chemistry. According to my initial attempts with online calculators, it would likely be a matter of a couple of grams of gypsum and calcium chloride. While that doesn’t sound like a lot, my guess is that it could actually be quite a bit of mineral to add and I’m not sure I want to waste a batch trying until I get a sense of proportion.

Any suggestions?

As usual, thanks for any and all help.[/quote]

99% of efficiency is about the crush. If you haven’t addressed that, start there.

Forget Palmer’s nomograph. It’s inaccurate and John has acknowledged that. Get a water analysis and get Bru’nwater.

Why do think lowering pH will improve your efficiency? What is your mash pH like now? Lactic or phosphoric acid is equally effective as acid malt for lowering pH and far easier to use.

3

What are you checking your ph with now strips or a meter ?

4

Thanks for the responses.

The way I deal with the crush is to run it through the mill twice at Northern Brewer. They’ve got the setting locked (and I believe it’s something like 0.4, but I forget what that’s measuring). In any case, without my own grain mill, this is probably the best I can do.

As for measuring pH, I used strips, but they’re really hard to read and by the time I read them, they’ve cooled off, so it’s not the exact pH of the mash. I realize you have to adjust the reading based on temp, but I honestly think the strips aren’t that helpful. All I could tell is that the mash pH MIGHT be between 5.6 and 6.0. Maybe I’m just not that good at distinguishing colors, but I don’t trust the strips.

Since I’m not sure if a pH meter is necessary at this time I’m not really sure if it’s a warranted purchase, given the price and the fact that you have to have standard solutions to calibrate that require changing, etc. I thought simpler measures like adding an acid rest or acidulated malt would be cheaper and less likely to create problems with my beer.

My understanding, based on what I’ve read, is that pH affects mash efficiency, but that the mash pH can be affected by the buffering system inherent in the water source, so the pH of the adjusted water may not be reflective of what you’ll get in the mash. Admittedly, I’ve not gotten through the water chemistry from the new book, “Water”, so it isn’t clear to me how my water source works as far as creating pH conditions with its buffering.

Finally, I get my water from the Mississippi River which, according to the water dept, has quite a variance based on the season, rainfall, etc. So, the water report they provide is fairly useless since the variation in readings can be extreme. I ran the averages that the water dept gave me through Bru’nwater and one other online calculator which is where I came up with the two grams of gypsum and calcium chloride. I thought that was a fairly large amount of chemical additions, especially if there is so much variation in the water supply (i.e., where do you aim if you don’t know where you are?)

5

Getting water chemistry under control can have big impacts on the flavor aspects of your beer, but they have minimal impact on the efficiency. As Denny said, efficiency is almost all due to crush, and in my opinion, the most important aspect of efficiency is consistency. If you are getting consistent efficiency numbers, you can plan effectively. I haven’t noticed much if any correlation between efficiency and beer quality. There is obviously a cost savings if your efficiency is high, but considering the price of malt that only matters if you are running a commercial brewery.

It sounds like it would be hard to get your water under control if you keep using a source that varies so much unless you invest in some test equipment. Using bottled water may be your only other option. To get around the quick-cooling problem, you may want to take an eyedropper of mash and place it on a plate to cool BEFORE you use you pH strips. That way, you are testing room temperature liquid which is what you want to be doing anyway.

6

[quote=“rebuiltcellars”]Getting water chemistry under control can have big impacts on the flavor aspects of your beer, but they have minimal impact on the efficiency. As Denny said, efficiency is almost all due to crush, and in my opinion, the most important aspect of efficiency is consistency. If you are getting consistent efficiency numbers, you can plan effectively. I haven’t noticed much if any correlation between efficiency and beer quality. There is obviously a cost savings if your efficiency is high, but considering the price of malt that only matters if you are running a commercial brewery.

It sounds like it would be hard to get your water under control if you keep using a source that varies so much unless you invest in some test equipment. Using bottled water may be your only other option. To get around the quick-cooling problem, you may want to take an eyedropper of mash and place it on a plate to cool BEFORE you use you pH strips. That way, you are testing room temperature liquid which is what you want to be doing anyway.[/quote]

I agree…while water chemistry can have an effect on efficiency, it’s a minor consideration. Have you ever checked your conversion efficiency? Take a look at this…http://braukaiser.com/wiki/index.php?ti … Efficiency

7

[quote=“Denny”]

I agree…while water chemistry can have an effect on efficiency, it’s a minor consideration. Have you ever checked your conversion efficiency? Take a look at this…http://braukaiser.com/wiki/index.php?ti … Efficiency[/quote]

+1 on Kai’s spreadsheet (linked on the same page Denny cited)

http://braukaiser.com/documents/efficie ... ulator.xls

It’s been really helpful in identifying my efficiency issues.

8

[quote=“Antwerp”]I’ve been getting about 75% efficiency with my single infusion, batch sparge mashes, but I suspect I might be able to do better. My water source is relatively soft and, when I plug the numbers into John Palmer’s nomograph on the back cover of “How to Brew”, it appears that my mash pH is around 5.8, suggesting my water source is most appropriate for amber colored beers.

I’m thinking about a couple of ways to lower the mash pH and make it more appropriate for the lighter style Belgian beers I brew (tripels, strong goldens, saisons, BPAs, etc). One would be doing an acid rest and the other approach would be adding acidulated malt.

I’ve heard that an acid rest may help to create acids by activating phytase, but that this takes quite a length of time to happen (hours?). A staff person at a homebrew supply store told me he does this (he uses the same water source and mash process as me) and his mash efficiencies are regularly in the mid 80s. I’m dubious and not too excited about trying to get the temperature right by adding more hot water to get the temp to mash temps since I’ve found the calculators don’t always work very well with water additions.

I’m frankly more interested in adding acidulated malt, but am unsure of how much I’d need to add – Palmer talks about up to 10%. I thought I’d start with 1% of my grain weight and add more in each batch to see what effect it has in mash efficiency.

Maybe I’m already fine with 75%, but if it’s just a simple matter of a few ounces of acid malt for better efficiency (perhaps even better taste), I’d say that’s great.

The third option is going to take me a little longer to understand – adjusting water chemistry. According to my initial attempts with online calculators, it would likely be a matter of a couple of grams of gypsum and calcium chloride. While that doesn’t sound like a lot, my guess is that it could actually be quite a bit of mineral to add and I’m not sure I want to waste a batch trying until I get a sense of proportion.

Any suggestions?

As usual, thanks for any and all help.[/quote]

I use the Grand ave store and find efficiencies around 80%. Before the rollers were changed and locked down my effic was in the doghouse as people were forking with the gap too much, so I crushed twice for about 6 months in 2011 to hit 80%. As of spring of 2012 to now it is right back to around 80% on one pass and depending on SG. Unless every beer you are doing is very high SG you should be hitting at least 75% on one pass. A double crush indicates to me that there is more in your process that needs adjustment. Now if you have clear enough runoff’s and no stuck sparges then whatever keep using the double crush I guess and adjusting your PH and calcium content will increase your effic slightly no matter what.

I use phosphoric 10% to lower mash PH, you can certainly use acid malt or even lactic acid. That is really weird that a NB staff member is using acid rests, I mean if you want to do a quad decoction and use every rest known to man, so be it but it is an awfully inefficient way to just hit your mash PH. Yup, forget the nomograph. In the past that might get you close and then you still were adjusting via old school, test, add, test, add etc… Bru n water puts you right close to the money I have found usually 0.1 to 0.3PH points around target at most if not spot on if your using the spreadsheet correctly. Thus bru n water will indeed help you hit PH and also adjust your minerals correctly with no fuss. It is very intuitive once you get the hang of it.

Where are you located? Minne or St Paul?
The reason I ask is Minne does blend “sanitized” ole Miss water with wells to produce tap water whereas St Paul utility runs the same Miss water up to Lino lakes and it then filters down through the chain of lakes to Little Canada where it is then pumped and blended with the wells to give us tap water. Just FYI if you weren’t aware of the huge difference between the two cities tap quality.

9

[quote=“Antwerp”]As for measuring pH, I used strips, but they’re really hard to read and by the time I read them, they’ve cooled off, so it’s not the exact pH of the mash. I realize you have to adjust the reading based on temp, but I honestly think the strips aren’t that helpful. All I could tell is that the mash pH MIGHT be between 5.6 and 6.0. Maybe I’m just not that good at distinguishing colors, but I don’t trust the strips.

Since I’m not sure if a pH meter is necessary at this time I’m not really sure if it’s a warranted purchase, given the price and the fact that you have to have standard solutions to calibrate that require changing, etc. I thought simpler measures like adding an acid rest or acidulated malt would be cheaper and less likely to create problems with my beer.

Finally, I get my water from the Mississippi River which, according to the water dept, has quite a variance based on the season, rainfall, etc. So, the water report they provide is fairly useless since the variation in readings can be extreme. I ran the averages that the water dept gave me through Bru’nwater and one other online calculator which is where I came up with the two grams of gypsum and calcium chloride. I thought that was a fairly large amount of chemical additions, especially if there is so much variation in the water supply (i.e., where do you aim if you don’t know where you are?)[/quote]

#1 when using brunwater you as a newer brewer really dont need a PH pen. Others like myself that have owned and used PH pens for years have already found the formulas used in brunwater and Kai’s app on brewers friend.com are super close to spot on. The only time having a pen is useful is when using unknown grain types or tons of wheat or other adjuncts. Again you can use these apps to get you close enough with weird grist’s then you adjust again per your PH reading. But 95% of the time brunwater w/o a PH reading is more than ample.

#2 it looks as though your close, be it Minne or St Paul it takes small amounts to find mineral needs for our supply, like you are finding a few grams here and there is correct. I can speak to St Paul water specifically, but I find the monthly reports to be very,very,very close and find I can use them reliably. You are always a month behind in reporting, but the only thing that really changes is Alkalinity and not by much.

Here is an example.
Sept 2013 was reported as 48 ppm Alkalinity and we are yet to see Oct 2013, Well knowing our supply now and the fact that we had low rainfall all fall leads me to imagine this number should be closer to 55 on November 7th when I brewed a Helles. I also have over 5 years of monthly records to compare wet/dry years and looking back at drier Novembers showed 55-60ppm.
Guess what. When I added a dash more acid to compensate for a higher ppm I was right on the money in thinking we are currently around 55ppm. Now this is speaking to super accuracy if you want it, whereas had I shot for the 48ppm I would still be close, but probably about 0.1PH off the mark instead of spot on. Our water doesn’t really change horribly fast from month to month and it will be gradual where you can figure it out in most cases. Unless lets say Sept 2013 was reported as 48ppm and we had rain most of Oct 2013 then you can be assured that the 48ppm probably dropped to 40ppm at the most instead of rising to 55/60.

Now if you are using only Minne’s (annual?) reports or other then yes it could look as though it swings greatly when in fact it is only minimal at best from month to month. I looked once for a buddy in Minne and gave up as I didn’t readily find the muni info I wanted, whereas had I taken the time I am sure I could find better info at least on a quarterly basis. Or email every quarter if I used that supply.

Here is another example of St Paul supply for 2012 I am only listing alk as the other minerals do not really change all that much 1-5 ppm at most which is peanuts in the scope of things:
Jan: 55ppm
Feb: 56ppm
Mar: 52ppm
Apr: 46ppm Now this dropped dramatically because we had tons of flooding in spring of 2012 and this flooding continued throughout the summer until July. It was a strange year, definitely not typical.
May: 45ppm
Jun: 48ppm
July: 46ppm
Aug: 57ppm Now this went up for the rest of the year as we saw very little rainfall throught the end of the season.
Sept: 60ppm
Oct: 62ppm
Nov: 62ppm
Dec: 62ppm
So around 55ppm on average, and depending on month using the 55ppm number would put you awful close to the mark. If you really want fanatically accurate alkalinity you can use a titration setup as used to test aquariums then you would know what the current alk is for a fact.

10

Thanks for all the good feedback!

I’m going to look into the conversion efficiency – thanks, Denny.

I live in a suburb of Mpls and we get our water from Mpls water treatment plants. Talked to them today (VERY helpful) and confirmed your observations, ITs, that there isn’t a LOT of variation over the course of the year. They said most the variation is in the spring runoff and after big rainfalls, but didn’t mention the low rainfall issue with alkalinity, so maybe I’m looking at this issue at the best time since we really haven’t had much rain and the alkalinity is rising. Thanks for the suggestion about that, ITs!

I’m not so sure that a double crush is doing too much. I can’t see a correlation with my mash efficiency, but I nearly never brew the same kind of beer twice now in my exploratory phase of brewing. I went to a double crush on the advice I’d seen Denny give on this forum to someone else. Given the fact that I’m fairly consistent on mash efficiency (74 - 83% at the extremes and nearly all others clustering around 76%), maybe I should be thinking about the addition of chemicals to the kettle. I’m not sure if another 4% or so is all that imperative. Beside improving mash efficiency, my goal with water treatment was to get a little more “definition” to the flavor of my beer since they now seem to have flavors that run together a bit more than the commercial examples. My sense in running through the Bru’nwater and Brewer’s friend calculators was that the style I was focused on (light color) seemed to move toward a higher sulphate/chloride ratio for better hop flavor expression, so in my last batch, a Saison, I added a gram of gypsum to the kettle to see if that relatively small ratio change would have any effect. I’ll know more in a month or so.

So, if I still want a bit more mash efficiency and lower the pH via acidulated malt, do you have any suggestions about the amount I’d use? I’m thinking a half pound which would be about 4% of the grain bill, based on my average amount of grain in my recipes. I’m puzzled why that would be harder than adding a food grade acid – do you mean in terms of predicting the amount of acidification?

Thanks again!

11

Yes, absolutely. You will definitely see more flavor clarity from style to style now as our water always leans towards the very malty side, so slight gypsum additions are warranted to achieve balance to bitter depending on beer.

You can accurately add acid malt into the grist equation on either mentioned spreadsheet/app and you will find it as accurate as adding in acids into the apps.

Let me give you a really good example. Matter of fact when looking over these numbers again I see the mash hit 85 to darn near 90% effic on this beer which is unusual for my setup as I typically don’t surpass 85% on any beer. Crush was same similar to norm also.
This is for my Innkeeeper bitter, which is pretty much stock NB recipe with a slight change to the crystal malts and a boost to base malt to hit 6.5 gallon postboil. So I input the following.
Water input for Sept 2013
Ca: 23
Mg: 6
Na: 18
SO4: 12
Cl: 37
HCO3: 59 ( You can times alk x 1.22 to find HCO3)
Alk: 48
Grist input for Innkeeper
4.0 gallons mash/ 6.5 gallons postboil.
8.5# Golden promise (2L)
0.30# Weyermann Caramunich I (34L)

So for the mash I added 0.6g lime to add calcium without adding unneeded chloride you will get with CaCl. Then add 1.2g gypsum to bring the ratio up to 1.5(balance to slight bitter) Then I added 11.0ml of Phosphoric 10% to hit 5.6PH at room temp meaning 5.3PH at mash temp.

So by these additions my calcium was boosted from 23ppm to 63ppm.
My flavor ratio was also now corrected and I hit an optimal PH for the mash.

Now If I leave everything else alone and omit the phosphoric acid used and use acid malt in the matrix instead I find the mash would only need a quarter pound of acid malt to hit 5.6PH(room temp measurement/ 5.3PH at mash temp)

Now this is where more precise alkalinity would be beneficial for me at least as I fly sparge, so I am diligent to reduce my sparge liquor PH to under 6.0. Now when having to guess the 5-10 points of alkalinity matters is most months I can use the sparge acid tab in brunwater to find a typical sparge PH of 5.6 also. Well early months and later months are tricky sometimes as many times I am shooting for 5.6PH and make a appropriate acid addition and sometimes it is 5.2 or 5.9PH when I test it during sparge. Which is not a be all end all either as most times my last runnings are in check to what I would normally expect but off ever so slightly but still well under 6.0PH at any rate. But it would be nice to know precise alk for this operation only so I know what my preboil PH will be thus being able to gauge post boil and post ferment PH, now we are talking real semantics huh… Where as mentioned above If I feel the bug one day I will start using a cheap titration kit as mentioned by Kai(braukaiser) and AJ Delange.

At any rate I will mention my sparge additions for posterity. I add to sparge only, no minerals goto the kettle directly.
Innkeeper sparge additions for (7) gallons.
3.4g gypsum
1.0g CaCl
12ml Phosphoric 10%
Now again this beer was a good example as I used Sept alk of 48 when it was probably closer to 55-60 in October when I made this beer. So instead of hitting 5.6PH with 12ml, I hit 5.95PH
Now after the brewday was done I can also use the app to back calculate what my alkalinity probably was. That’s why I was able to make a better judgement call on Novembers helles along with my prior data on the supply as my PH’s were perfect across the board for that brewday.

12

Good plan. If you are getting reasonably consistent efficiency, don’t focus on that, and as already said, water chemistry won’t make any significant difference in efficiency. Water chemistry CAN help you with the better defined flavors you are trying to achieve.

13

Follow up.

I plugged in my water data to the Bru’nwater spreadsheet for my next beer, a Saison Noel, and, assuming I’m using the spreadsheet correctly, found that by adding just a quarter pound of acidulated malt (I think this is what they are referring to by the term “acid malt”), and NO mash water corrections, the mash pH measured at rm temp was 5.4. I think this may be the easiest approach for me, barring any ill effects on taste by the acidulated malt. I could then do chemical additions to enhance flavor clarity in the kettle. Since I batch sparge, I don’t believe I’d have to do any pH corrections for my sparge water.

However, my source water is fairly low in Ca at 23ppm, so would it be prudent to increase that up to 50ppm (what I’ve read as the minimal necessary level for mashing)? Maybe this would be the only other component of a moderate attempt toward a good mash beside the acidulated malt.

Does this sound like a reasonable approach?

Thanks again ITs for a very detailed and helpful lesson using our region’s water as an example. It doesn’t appear that Mpls and St. Paul water are appreciably different for brewing.

14

Sounds like you’ve got it nailed!

15

I suspect I don’t, at least not nearly enough. But I’m starting to get a handle on one more piece of the puzzle. Having said that, my beers are definitely getting better and the process of learning the art and science of brewing gets even more fun. Soon I’ll be moving into the creative part of brewing. Friends enjoy the product of my improvements. It’s a great hobby!

Thanks to all for enduring my naive questions – ones I’m sure you’ve answered many times over.

:cheers:

16

[quote=“Antwerp”]Follow up.

I plugged in my water data to the Bru’nwater spreadsheet for my next beer, a Saison Noel, and, assuming I’m using the spreadsheet correctly, found that by adding just a quarter pound of acidulated malt (I think this is what they are referring to by the term “acid malt”), and NO mash water corrections, the mash pH measured at rm temp was 5.4. I think this may be the easiest approach for me, barring any ill effects on taste by the acidulated malt. I could then do chemical additions to enhance flavor clarity in the kettle. Since I batch sparge, I don’t believe I’d have to do any pH corrections for my sparge water.

However, my source water is fairly low in Ca at 23ppm, so would it be prudent to increase that up to 50ppm (what I’ve read as the minimal necessary level for mashing)? Maybe this would be the only other component of a moderate attempt toward a good mash beside the acidulated malt.

Does this sound like a reasonable approach?

Thanks again ITs for a very detailed and helpful lesson using our region’s water as an example. It doesn’t appear that Mpls and St. Paul water are appreciably different for brewing.[/quote]

Your more than welcome, glad it helps.
As highlighted above the room temp measured mash sample will always reside about 0.30PH points above what the true mash temp PH is. But we want to take or measure PH at room temp for a variety of reasons. So if you shoot for 5.4 (room temp) which bru n water is showing you. Your actual mash PH will hover around 5.10. For this style of beer I would shoot for 5.6 at room temp, thus giving you a mash PH of 5.3

Usually you want the mash to reside in between 5.2-5.5 if measured at mash temp. So 5.5 -5.8 if measured at room temp. Most times you will reserve lower mash PH’s(5.2)for lighter beers like regular saison, pils, bitter etc… and use higher PH’s (5.5) for maltier styles. If not sure just shoot for middle ground of 5.3PH(mash)and 5.6PH(room)

Yes, I would suggest boosting Ca a tad bit. Calcium will naturally help drive down PH slightly and most importantly helps with hot/cold breaks and yeast health. Wish I could post a video shot of the helles done a week ago, absolutely stunning break. You could add just a pinch of lime which will kick up the Ca without adding any chloride. You will probably find the quarter pound works with the lime in place. If nothing else you can back off the acid malt just an ounce.

17

OH, one last big note to mention on water manipulation.

St. Paul supply at least uses very high levels of chlorination via chloramines to disinfect the water supply. The EPA highest rating is 4.0 and we sit around 3.0-4.0 in St Paul. So I use 1/4 tab of campden per 5 gallons of water to remove chlorine and byproducts.

18

ITsPossible, I think you put a typo in there. You want the mash pH to be in the 5.2-5.5 range if you measure the sample at room temperature.

19

No, everything stated is correct Rebuilt.

#1 If you measure the mash PH at room temp it will be 0.30PH higher than if tested at mash temps of 145-162.

#2 You want to test at room temp for both longevity of probe life and consistent sampling procedure/results.

#3 Most common home brewer pens will only function/show a correct test value under 140f.
So it is next to impossible to test at true mash temps unless you want to do some math yourself as ATC is not setup to make a correction over 140f.

So if your willing to do the temperature correction math yourself and take a sample of a typical mash that should be at lets say 5.3PH. In theory here is what would happen.
A. At lets say 150f mash rest you take a sample showing 5.3 at the mash temp.
B. You would then see this same sample if cooled to room temp would be showing closer to 5.55-5.60PH.

So the range for room temp samples to shoot for is indeed 5.5-5.8PH
Which would be true mash values of 5.2-5.5PH

20

Um, No video but I did happen to shoot a couple of still pics of the brewday that captured the break.
So here is some beer pron.

Kettle full, I have to come close to the top on my 7.5 gallon kettle in order to end up with 6.5 gallon post boil. I need a new kettle especially for lagers. Next year maybe. I do not use foam stuff I can just keep the boil manageable until the volume drops. Unfortunately I do have to skim foam to prevent boilovers no matter what. Thats why I really want a bigger kettle also so I dont have to skim either.
[attachment=2]Kettle full.JPG[/attachment]

Just starting boil.
[attachment=0]boil1.JPG[/attachment]

20 minutes into boil, you can see the flocs getting bigger.
[attachment=1]boil.JPG[/attachment]