Electronic ph meter

[gregorach]

Yeah, I've become extremely sceptical about the value of pH strips since buying a decent meter.

When calibrating, bear in mind that the buffers are surprisingly sensitive to temperature...

[Dave S]

Does anyone know where to get buffer solution at a reasonable price? Mine cost just short of a tenner for a 250 ml 7,4 pair and they don't tend to last very long.

[greenxpaddy]

Yeah, I've become extremely sceptical about the value of pH strips since buying a decent meter.

When calibrating, bear in mind that the buffers are surprisingly sensitive to temperature...

My ph meter has thermometer also so I guessed it was factoring in the temp at all points...?

[gregorach]

Yeah, but the buffers themselves are only accurate at the correct temperature, and they're surprisingly sensitive to variations. Your typical 7.01 pH buffer is only actually 7.01 pH at exactly 25 degrees (or whatever it states on the bottle). The temperature correction for the meter is an entirely separate matter. Calibration must be performed at the correct temperature. Usually this requires placing the containers holding the buffers into a water bath - ideally thermostatically controlled, but you can just about get away with adjusting the temperature with hot or cold water until your buffers are at their correct temperatures. Only then can you proceed to calibrate the meter - otherwise, you're actually de-calibrating it.

[Hogarth]

Yeah, I've become extremely sceptical about the value of pH strips since buying a decent meter.

How inaccurate have you found the PH strips to be, Dunc?

[greenxpaddy]

Yeah, but the buffers themselves are only accurate at the correct temperature, and they're surprisingly sensitive to variations. Your typical 7.01 pH buffer is only actually 7.01 pH at exactly 25 degrees (or whatever it states on the bottle). The temperature correction for the meter is an entirely separate matter. Calibration must be performed at the correct temperature. Usually this requires placing the containers holding the buffers into a water bath - ideally thermostatically controlled, but you can just about get away with adjusting the temperature with hot or cold water until your buffers are at their correct temperatures. Only then can you proceed to calibrate the meter - otherwise, you're actually de-calibrating it.

Flipping heck. The manual didnt say that. The other thing was it said it recognises the 7.0ph solution on calibration. I then thought it would measure temp and calibrate it knowing the buffer temp versus accurate ph7.0. That is clearly possible....

[orlando]

Does anyone know where to get buffer solution at a reasonable price? Mine cost just short of a tenner for a 250 ml 7,4 pair and they don't tend to last very long.

I've got this, they also do a pH 4 bottle too. The two cost £8 a piece delivered.

[Dave S]

Does anyone know where to get buffer solution at a reasonable price? Mine cost just short of a tenner for a 250 ml 7,4 pair and they don't tend to last very long.

I've got this, they also do a pH 4 bottle too. The two cost £8 a piece delivered.

That's even dearer than mine, Orlando. I got these also from Amazon.

[orlando]

Apologies I didn't read the post properly and missed you had put for the pair, I thought you meant a tenner each.

[Dave S]

Apologies I didn't read the post properly and missed you had put for the pair, I thought you meant a tenner each.

There must be someone doing them cheaper. I've had 6 at most calibrations out of mine and they need replenishing. Gets to be a dear do, this brewing lark.

[Dave S]

Interestingly, I've just bought a copy of my very first brewing book, 'Brewing Better Beers' by Ken Shales. Mostly out of nostalgia really, as it was only 1p + del. Having had a quick skim through I don't think there's a single mention of pH .

[gregorach]

Yeah, I've become extremely sceptical about the value of pH strips since buying a decent meter.

How inaccurate have you found the PH strips to be, Dunc?

It's been a while, I can't actually remember.

[gregorach]

Yeah, but the buffers themselves are only accurate at the correct temperature, and they're surprisingly sensitive to variations. Your typical 7.01 pH buffer is only actually 7.01 pH at exactly 25 degrees (or whatever it states on the bottle). The temperature correction for the meter is an entirely separate matter. Calibration must be performed at the correct temperature. Usually this requires placing the containers holding the buffers into a water bath - ideally thermostatically controlled, but you can just about get away with adjusting the temperature with hot or cold water until your buffers are at their correct temperatures. Only then can you proceed to calibrate the meter - otherwise, you're actually de-calibrating it.

Flipping heck. The manual didnt say that. The other thing was it said it recognises the 7.0ph solution on calibration. I then thought it would measure temp and calibrate it knowing the buffer temp versus accurate ph7.0. That is clearly possible....

Nah, the temperature correction in the meter is to correct the response of the electrode, which also varies with temperature.

[Eric]

Yeah, I've become extremely sceptical about the value of pH strips since buying a decent meter.

How inaccurate have you found the PH strips to be, Dunc?

It's been a while, I can't actually remember.

How accurate need we be Dunc? Better than a point or two?
I don't have a meter and so can't validate an argument, but have we advanced beyond balancing buffers to enable the brew to do what it can do best?

Yeah, but the buffers themselves are only accurate at the correct temperature, and they're surprisingly sensitive to variations. Your typical 7.01 pH buffer is only actually 7.01 pH at exactly 25 degrees (or whatever it states on the bottle). The temperature correction for the meter is an entirely separate matter. Calibration must be performed at the correct temperature. Usually this requires placing the containers holding the buffers into a water bath - ideally thermostatically controlled, but you can just about get away with adjusting the temperature with hot or cold water until your buffers are at their correct temperatures. Only then can you proceed to calibrate the meter - otherwise, you're actually de-calibrating it.

Flipping heck. The manual didnt say that. The other thing was it said it recognises the 7.0ph solution on calibration. I then thought it would measure temp and calibrate it knowing the buffer temp versus accurate ph7.0. That is clearly possible....

Nah, the temperature correction in the meter is to correct the response of the electrode, which also varies with temperature.

Now I've read that pH is influenced by temperature and that of buffer solutions will vary with temperature, but that variation is in some way proportional to the pH, such that it is my belief that any variance isn't really significant over the range of temperatures and pH in brewing and correction is necessary only for the instrument in use. But why calibrate at pH 7 when brewing starts with a mash that is roughly fifty times more acidic than that level? To me that would be similar to calibrating your mash thermometer at either 17,000 or minus 205 degrees centigrade.
In 1909 Sorensen introduced p[H] to the world after using a galvanometer in place of colour sensitive strips to measure the ion concentration of enzyme activity in proteins in the Carlsberg Laboratory. I wonder if his purpose and methods were intended for the advancement of brewing? A few years later institutions took his work and changed his definition, adapting it for pure science such that I wonder if that is why today brewers struggle to know what it means?
Certainly I'm baffled.

[gregorach]

How accurate need we be Dunc? Better than a point or two?

As as been observed elsewhere, I'm a bit OCD when it come to numbers... But the inaccuracy I noticed in my pH strips was certainly of the order of several points. I just can't remember exactly how many. Could even be up to +/- 0.5.

But why calibrate at pH 7 when brewing starts with a mash that is roughly fifty times more acidic than that level?

Because 7.01 and 4.01 are the standard calibration points for all pH meters. Those are the calibration buffers you can buy most easily, and they're the values the meter is expecting when you put it into calibration mode.