ooh look another water treatment question

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wilfh
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ooh look another water treatment question

Post by wilfh » Wed Feb 14, 2018 8:22 pm

with my shiny new pH meter I've started taking readings and that's when the trouble started.
Murphy's tested my water and gave me the following readings

Calcium 17
Magnesium 1
Chloride13.01
Sulphate 29.89
Alkalinity 21

My salifert tests have always come out a consistent 22 (0.9 mil of KH reagent- 0.45 meg/l= 22.5)
Murphy's suggested that I should add DWB at 0.96g per litre which gave 6.88 ppm per litre of Ca or 29g for a 30 litre batch.
Cue pH meter
I've done 2 batches and I've had 2 readings of 5.8 and 5.9 (voltcraft ph-100 ATC) in the mash which I take it is too high. Right?
Before I dive into pH adjustment for next time does the above sound reasonable or have I messed something up which is why the pH reading is high. I thought the DWB adjustment was designed to bring the pH of the mash down to 5.2-5.5?

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Wilf

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Aleman
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Re: ooh look another water treatment question

Post by Aleman » Wed Feb 14, 2018 8:56 pm

Have you calibrated the meter? IIRC the voltcraft will do a 2 point calibration with buffers at pH7 and pH10
At what temperature did you measure the pH? Ideally room temp. IIRC at mash temps you take 0.3 from the pH reading so pH 5.5 and pH 5.6
When did you measure the pH? Ideally 10 minutes after mashing in.

My process is to calibrate the meter on the day and store in distilled water ready to use. Mash in, and then after 10 minutes draw off a sample of the liquid. I use a shot glass kept in the freezer so the temp drops to 20C pretty quickly. Measure the pH, record it and proceed. If it's not where I expect it I generally have a look for the treatment salts as it means I've forgotten to use them :oops:

I've always though pH 5.2 is too low for mashing and would never go lower than 5.3, more usually 5.4.

Using your probe at mash temperatures is a good way to destroy it pretty quickly ;)

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Eric
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Re: ooh look another water treatment question

Post by Eric » Wed Feb 14, 2018 8:58 pm

Well I calculate that amount of DWB will add about 170mg/L of calcium. I agree your mash pH should be less than you've measured whatever grist you used.
Do you do a full volume mash? That would increase nominally increase mash pH, but maybe not to what you have found. Has the meter been correctly calibrated?

Damn, beaten again.
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Re: ooh look another water treatment question

Post by wilfh » Wed Feb 14, 2018 10:38 pm

Hi Eric Aleman,
Yes calibrated in 7 and 4 buffer before hand.

I mashed in with about 2 litres per kg as the mash tun is a bit small

I tested about about 15 minutes in (well acutally did one immediatly but that was 6.2 and came down to 5.8 at 30C. I thought the meter was supposed to make the calibration itself.

The DWB went in with the grain.

could very well be operator error but if so I've done the same thing twice now!

Cheers
Wilf

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Re: ooh look another water treatment question

Post by orlando » Wed Feb 14, 2018 10:41 pm

Aleman wrote:
Wed Feb 14, 2018 8:56 pm
Have you calibrated the meter? IIRC the voltcraft will do a 2 point calibration with buffers at pH7 and pH10
Two screws to calibrate 4 and 7/10. I just use 4 and 7 with mine. Make sure you store the probe in pH probe storage solution and as Aleman says don't go sticking it in hot mash. Rinse with deionised water and you too could have a probe that has so far lasted me 4 years. :D
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Re: ooh look another water treatment question

Post by Jocky » Thu Feb 15, 2018 8:11 am

The voltcraft meter took me a while to get the hang of, but after I did my readings were rock solid consistent.

As Ashley had said definitely store it in the right probe solution, and both before use and between each test you will need to rinse it in deionised water (a tattoo wash bottle helps for this) and then give it a quick pat dry with kitchen towel.

Along with only testing cooled samples, the probe will last a long time and barely drifts over months between usage - although I still check calibration the day before a brew day.
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Re: ooh look another water treatment question

Post by Kev888 » Thu Feb 15, 2018 12:17 pm

wilfh wrote:
Wed Feb 14, 2018 10:38 pm
Yes calibrated in 7 and 4 buffer before hand.. <snip>..I thought the meter was supposed to make the calibration itself.
It sounds like you have done the manual calibration: IIRC set the pH to 7.0 in the pH 7 solution, and then set the slope to 4.0 in the pH 4 solution - its then wise to check a measurement of the pH7 solution again afterwards to see if an iterative approach is needed. Wash then dry off the probe between each solution so as not to transfer much of one solution to the other. Gently swirl the probe a bit in the solution and wait until it has stabilised before making any adjustments - sometimes if you wait the reading changes a little as it settles.

The temperature calibration is automatic (ATC)... but has its limitations and the pH range that you are actually aiming for is different at different temperatures, which can be confusing if combined with ATC. Plus, measuring hot wort is less kind on the probe; these need replacing periodically but last much longer if you treat them nicely. So all in all I'd follow Aleman's suggestion and just do it all at room temperature, at least to start with.
Kev

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Re: ooh look another water treatment question

Post by wilfh » Thu Feb 15, 2018 2:10 pm

Thanks All,
I've done everything else (bar the 30C reading vs 20C) but drawing a bit of a blank. Will have another go at calibration but it was bang on after I played with the screws.

DWB doesn't deteriorate does it?(I don't think so but I'm questioning everything I'm doing at the moment)
Cheers
Wilf

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Eric
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Re: ooh look another water treatment question

Post by Eric » Thu Feb 15, 2018 2:36 pm

I think you are going to have to let this one go, you would seem to have examined everything you can.
Your DWB might have absorbed some water from the air, but even that wouldn't cause the sort of discrepancy you found.
You could do a mini mash in the kitchen oven with about 50g of pale malt. Then as Aleman tells us, use a shot glass from the freezer to chill the wort before you measure pH
If wanted, you can pop over here when convenient with your meter and do a comparison.
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Re: ooh look another water treatment question

Post by Jocky » Thu Feb 15, 2018 3:50 pm

Kev888 wrote:
Thu Feb 15, 2018 12:17 pm
Gently swirl the probe a bit in the solution and wait until it has stabilised before making any adjustments - sometimes if you wait the reading changes a little as it settles.
I forgot to mention that too - my voltcraft meter takes a good 30 seconds to creep towards a final value.
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Re: ooh look another water treatment question

Post by wilfh » Fri Feb 16, 2018 2:00 pm

Thanks Eric,
I'm going to start again with the calibration and have another go. if that fails I may just take you up on your offer :D

Jocky- It did take a while to settle down to two decimal places but I guess that's normal!

Wilf

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Re: ooh look another water treatment question

Post by Carnot » Fri Feb 16, 2018 4:14 pm

Maybe your problem is due to the new electrode even if you have done the calibrations correctly. By chance was it dry or wet when unpacked? The electrode membrane might need regenerating or possibly if the lectrode has been stored in demin water there has been some leaching of the electrolyte. Normally the storage solution should be the same as the electrolyte- typically KCl. Here is a link that should help and will be applicable to most pH meters. The sluggish or drifting response is not normal and suggests possible leaching, but it equally might be something else. Most problems can usually be traced back to the probe one way or another.

https://www.all-about-ph.com/ph-electrode-storage.html

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Re: ooh look another water treatment question

Post by orlando » Fri Feb 16, 2018 6:32 pm

Carnot wrote:
Fri Feb 16, 2018 4:14 pm
Maybe your problem is due to the new electrode even if you have done the calibrations correctly. By chance was it dry or wet when unpacked? The electrode membrane might need regenerating or possibly if the lectrode has been stored in demin water there has been some leaching of the electrolyte. Normally the storage solution should be the same as the electrolyte- typically KCl. Here is a link that should help and will be applicable to most pH meters. The sluggish or drifting response is not normal and suggests possible leaching, but it equally might be something else. Most problems can usually be traced back to the probe one way or another.

https://www.all-about-ph.com/ph-electrode-storage.html
I found a new battery helped a lot. :D
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Eric
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Re: ooh look another water treatment question

Post by Eric » Fri Feb 16, 2018 6:46 pm

wilfh wrote:
Fri Feb 16, 2018 2:00 pm
Thanks Eric,
I'm going to start again with the calibration and have another go. if that fails I may just take you up on your offer :D

Wilf
You're more than welcome to call across Wilf. I've plenty time being retired, but spend a fair amount of it getting out enjoying myself, so just a matter of fixing a time.
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Re: ooh look another water treatment question

Post by MashTim » Fri Feb 16, 2018 7:47 pm

What’s the grist?

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