Best water treatment for AG London Porter, for a Londoner?

[BrewBoyJoe]

I made an attempt at Fuller’s London Porter on Saturday following Graham’s recipe! I’m a bit sketchy on the water treatment regime for porter! I live in London and my Salifert alkalinity kit consistently gives a reading of around 230mg per litre Calcium Carbonate. For this reason I assumed the hardness of the water would compensate for the acidity of the grain bill in London Porter, giving the required optimum mash pH with no water treatment necessary! However, the pH 10 – 15 mins into the mash, according to my strips was 4.7 or so. To compensate I chucked about 6 or so heaped teaspoons of precipitated chalk! This took it up to almost 5.0! I was reluctant to put anymore in! I understand that as part of the normal process, the mash pH will drop throughout the 90 mins incubation? Is this correct? Then at what point do you stop trying to adjust the pH to 5.2 / 3? Do most people use chalk for this? Does anyone put any gypsom or Epsom salts in? I perhaps wouldn't expect this in the mash, but how about the boil for porter?

In this case my efficiency was around 79%, and I reckon there was still some sugar to be had! Because I brewed 50 litres instead of my usual 30, I had a lot of grain to sparge, so recirculated some wort to make sure I’d properly rinsed out the sugar! This brought things up by about 5% compared with usual! Although this is the first porter I’ve made! Because of the recirulation, the sparge temp dropped a bit here and there from the optimal 80 degrees but this doesn't seem to have impacted upon the efficiency!

[mabrungard]

Unfortunately, it appears that your pH strips lied to you. It's very unlikely that the grist for a Porter would push the mash pH as low as reported, especially with the amount of alkalinity in that water. pH strips are notorious for under-reporting the pH in mashes. I assume these were paper strips and they are quite unreliable under any brewing use. The plastic ColorpHast strips are better, but even they under-report the mash pH be about 0.2 to 0.3 units. They are otherwise consistent.

Your mash pH was probably much higher than reported. Hopefully, not so high as to cause unwelcome flavor effects such as a roughness in the hop flavor.

[BrewBoyJoe]

Yes I feared as much! Correct, I used paper strips! Still, if my mash pH was dramatically out, would the efficiency be so high? I will buy some more of the plastic pH strips!

[mabrungard]

I don't find that mash pH has a huge effect on extraction efficiency, but it does have a big effect on wort fermentability.

[BrewBoyJoe]

ok, that's interesting. From what I understand, porter takes quite a long time to mature, so I expect this beer will not be drinkable for a month, and will most likely improve to something quite nice by 2 months, if I haven't wrecked it with my shenanigans. I was sceptical of the mash pH reading at the time and so only adjusted from 4.6-7ish to pH 4.9ish. The strips would have to be out by a long way to cause problems for the beer! I will definitely look into the brand you suggested

I did some Googling and temperature at which the reading is taken seems to be very important. I had no idea about this!

See this text I found on HomeBrew Talk....


When the pH of a sample is measured it is also important to know the temperature of the sample. This is important for 2 reasons. The temperature of the sample affects its H+ concentration and therefore its pH. This is the result of changing H+ and OH- dissociation balances in the sample and is substrate specific. For wort it has been reported that the pH at mash temperatures (65 C/150 F) is about 0.35 pH units lower than at room temperature and at mash out temperatures (75 C/170 F) it is even 0.45 pH units lower [Briggs, 2004]. While my own experiments showed only a ~0.2 pH difference between a sample at mash temperature and a sample at room temperature (25 C/77 F). The temperature dependent change of pH is also important for the calibration of the pH meter since the buffer solutions have their nominal pH only at a specific temperature. This temperature is usually room temperature (25 C/77 F) and many buffer manufacturers supply tables with their buffers that show how their pH changes with temperature. I have made it a habit to always calibrate my pH meter with buffer solutions at room temperature (25 +/- 1 C).

[mabrungard]

You will find that the ColorpHast strips are not cheap. That is rather off-putting. But a good technique for their use is to cut the strips in half. That way you get twice as many uses. They reportedly have a limited shelf life, just like the paper strips, so don't buy a whole pack for yourself. Find someone to share them with.

The pH and temperature information presented above is from Kai Troester and I've found him to be a reliable information source.

[BrewBoyJoe]

ok great! Thanks for the tip. The fermentation has stuck at 1.022 on day 4! It's all gone to the bottom! Nothing on the surface! I have two separate plastic fermentation vessels on the go and both are stuck! I roused it trying not to get any air but mixing the yeast quite a lot! Hopefully this will do the job but I won't hold my breath!