[Phil_M]

Recently I posted on here about how I failed to get a low enough pH when mashing. Several folks recommended that I use Bru'n water to calculate water additions on my next batch. So I did, and aimed for a target 5.2 pH on the Saison I've been wanting to brew.

This time I undershot the pH, quite drastically. First reading was pH 4.5, and that was a 75 degree sample. I was hoping that the pH meter had a problem, but I had terrible efficiency so that backs up the meter.

I don't have the additions I used in front of me, but I used all distilled water. (All the RO water I found in my area was treated with sodium bicarbonate )

I'm going to start thinking about how I may be able to mash with less water, hopefully that will help make the chemistry easier. Also may accelerate plans to upgrade to a three vessel system.

I don't get it. Anyone have any input as to what about BIAB is making hitting a specific mash pH so difficult?

[pete b]

Are your brewing salts mixed into your mash or sitting on the bottom of your kettle under your bag. Some don't easily go into solution.

[Phil_M]

I usually prepare my water the night before. Add everything to the kettle, stir until everything is dissolved. I'll often heat the water up a bit to help everything dissolve as well.

On brew day I'll check and make sure nothing has precipitated out of the water, then I'll start heating it up and and the bag.

[dkfick]

Volume of mash water shouldn't make a difference as long as you're inputting the correct volume in Bru'n Water.  If you're adding acid make sure it's at the correct type and %.

[Phil_M]

I double checked all of that as well. 10% phosphoric acid solution, 8.75 gallons for the mash volume.

[mchrispen]

It is nearly impossible to achieve a 4.5 mash pH - even if intending too.

What was your grain bill? Did you calibrate your probe before use? Have you performed a stability test on it? (measure a buffer solution over several hours to see how accurate it remains over an extended period of time)

[Phil_M]

It is nearly impossible to achieve a 4.5 mash pH - even if intending too.

What was your grain bill? Did you calibrate your probe before use? Have you performed a stability test on it? (measure a buffer solution over several hours to see how accurate it remains over an extended period of time)

Couldn't too much phosphoric acid lower the pH too much?

The probe was calibrated about a month ago at pHs of 7 and 4.2, both at 72 degrees. I have not done a stability test.

If the probe was off, why the extremely poor efficiency?

[hopfenundmalz]

It is nearly impossible to achieve a 4.5 mash pH - even if intending too.

What was your grain bill? Did you calibrate your probe before use? Have you performed a stability test on it? (measure a buffer solution over several hours to see how accurate it remains over an extended period of time)

Couldn't too much phosphoric acid lower the pH too much?

The probe was calibrated about a month ago at pHs of 7 and 4.2, both at 72 degrees. I have not done a stability test.

If the probe was off, why the extremely poor efficiency?

I can't answer the efficiency question, but I find my pH needs to be calibrated before I use it in the morning, and if I am checking kettle pH or final wort pH I calibrate again after lunch.

[reverseapachemaster]

Low ph would definitely be a reason why you would have low efficiency but not the only reason for it. If that was the only variable you changed for a process that normally does not have efficiency problems then the ph is likely the sole culprit.

At 4.5 I am not sure you would have any conversion at 4.5, at least not without hours of mashing at fairly cool temperatures.

To get to 4.5 you would have had to add somewhere between 50-100ml of 10% phosphoric acid. Check the phosphoric acid. Is it possible you have 25% solution or higher?

[Phil_M]

Low ph would definitely be a reason why you would have low efficiency but not the only reason for it. If that was the only variable you changed for a process that normally does not have efficiency problems then the ph is likely the sole culprit.

At 4.5 I am not sure you would have any conversion at 4.5, at least not without hours of mashing at fairly cool temperatures.

To get to 4.5 you would have had to add somewhere between 50-100ml of 10% phosphoric acid. Check the phosphoric acid. Is it possible you have 25% solution or higher?

That could be where I went wrong. The bottle is clearly labeled "phosphoric acid 10%". I used 70 ml though, to try and get the pH down to 5.2.

Bought it from Northern Brewer here:
http://www.northernbrewer.com/shop/phosphoric-acid-8-oz-10-solution.html

I'm going to invest in some more pH calibration solution, and calibrate more often.

Is it more likely that the first reading was completely bogus, and the final 5.0 was correct-ish? pH was off enough for lousy efficiency but still ended lower than it should have?

I should point out that I despise pH meters. I've used them in school, they're always a pain. Using one in brewing is proving equally frustrating.

[mchrispen]

While I target 5.2 with my saisons, most of my beers shoot for 5.4 or 5.5, which gives me a little room for error if something is calculated right, and seems to benefit the styles I brew most often.

4.5 would have put mash pH at temp somewhere around 4.2... still wrapping my head around that.

The only other thing I can think is that perhaps some bits of malt may have stuck to the probe and altered the reading a bit... assuming the probe is working properly otherwise. I have seen that happen here - but rarely.

My MW102 takes a bit to stabilize - really my only complaint about it. So slope calibration before I grain in... and first reading about 15 minutes, which I expect to be off (but I have an idea if the mash is going ok) then again at 30 or 45 minutes... those latter are usually fairly close to my target.

One other thought, did you use aciduated malt? My mashes are more hit and miss with that. Liquid acid is so much more precise...

[Phil_M]

Didn't use acid malt, for the exact reasons you describe.

I've only got a cheap pH meter, and since I've only calibrated it once I no longer have a lot of confidence in it.

Once I get how I'll try and post all the details from the brew, ingredients, additions, mash schedule, etc.

[JT]

I have a decent meter and it still requires calibration every time I turn it on. 

[Phil_M]

Yeah, all roads are leading to needing to cal more often.

Here's the promised data:

Grist:

8 lbs Dingemans pilsner malt
2 lbs weyermann dark wheat malt

Water additions:

In 8.75 gallons of distilled water:

3.90 g gypsum
3.50 g epsom salt
2.60 g calcium chloride
70 ml 10% phosphoric acid

Bru'n water info:

Water adjustment tab:

Yellow Bitter target
8.75 gallons mash volume, 0 gallons sparge volume.
Mineral additions are listed in the top of this post.

Mash acidification:

Dingemans pilsner malt            base malt     8 lbs     1.6 L
Weyermann Dark Wheat Mat     base malt     2 lbs        7 L

I've got both listed as base malt. (Figure 7L dark wheat isn't nearly dark enough to be roasted.)

Mash steps:

Name                    Description                                           Step Temperat      Step Time     
Protein Rest            Add 34.99 qt of water and heat to 125.6           125.6 F       15 min       
Saccharification 1    Heat to 145.4 F over 11 min                           145.4 F       45 min       
Saccharification 2    Heat to 161.6 F over 9 min                             161.6 F       30 min       
Mash Out                Heat to 172.4 F over 6 min                            172.4 F       10 min       

First pH measurement was taken between 5 and ten minutes into the Sacch 1 rest. Final reading was taking at mash out.

[mchrispen]

The dark wheat malt... wonder if it is much more acidic. Dingeman's puts this around 12L, while Weyermans is around 8L - are you sure it's Weyerman? Still not enough to explain the dramatic difference. Perhaps Martin will swing by and comment.

I am leaning toward the probe. But I am seeing something different in my copy of Bru'n.

In a full volume mash BIAB, 8.25 gallons mash water... 100% Distilled Water

8# pils @ 3L
2# dark wheat at 8L

No mineral additions - only the 70 ml of 10% phosphoric, you are already at 5.0 estimated mash pH. I wonder if you didn't set the dilution percentage to 100% distilled and were working against a high alkalinity number? Or somehow changed the bicarbonate value in the table at the bottom of the Water Adjustment sheet?

If I add in your additions,

as listed, then the estimated mash pH is 4.85

If I reduce the phosphoric to just 28.9 ml, then the estimate mash pH is 5.24.