Malt vs. efficiency?

[David R]

I've done ten brews since going all-grain last year, mostly basic Pale Ale-type malt bills, and in general I've been getting fairly close to my expected OG with the weaker ones (missing by about 0.002 on beers around 1.040-1.050) but some of the stronger ones have been a bit further off their target (0.005-0.010 on beers around 1.060-1.075). Except for one that had 8% Caramel 90 (and the rest Golden Promise), which ended up at 1.060 instead of 1.055! I'm going to get stuck into How To Brew this weekend once I recover from tonight's nightshift and re-read the mashing and all grain chapters to try get a better understanding of pH etc, but could the reason for the better efficiency with that particular mash have been the darker malt helping to drop the pH? None of the others had anything that dark in them (IIRC Crystal 40L was about the darkest). And is it just coincidence that the higher OG beers have been missing out by a bit more, or does it get harder to get a higher efficiency as the OG gets higher?

I'm using rain water so it is about as soft as water gets, so I would have thought there would be no problems with the pH getting down.

[Jamie McQuillan]

Hey, You will probably get replies from people with more experience than me but I have gone through this recently myself. Yes higher gravity beers will have a lower mash efficiency. I have been working hard on this and getting there. Follow the advice in How to Brew and you will get there too. Yes darker malts will help bring down your pH. Use pH strips or a meter. I use the online brewers friend recipe builder which has a good water chemistry section (you can see the impact of the malts). Rain/soft water will be part of you problem. I recommend getting a waster analysis done (see How to Brew). 

[David R]

There's not much to analyse really. I've been keeping aquariums for ~18 years so know a fair bit about water already, and our tap water has 006-008PPM TDS (Total Dissolved Solids), for comparison pure Reverse Osmosis water will is zero and Auckland tap water IIRC is about 90PPM. General and carbonate hardness is undetectable, so the water is about as soft as it gets, free of any mineral content. Initially I thought my problem would be with the mash pH going too low (have that problem with the aquarium) but this has got me wondering if that isn't the case. I guess I really need to pick up some pH strips to test it. I'd like to brew a stout and/or porter for winter but would like to figure out what might happen with the much darker grains.

[Grant R Baker]

Have you tried letting your mash go a bit longer on the bigger brews..?

[Barry]

Batch or fly sparge?

[David R]

Haven't tried giving it any longer than an hour, will give it a go next time.

Barry, I'm doing a BIAB but mashing in a chillybin to try keep the temp constant. I guess it would be 'batch sparging', after the mash I drain the wort into the pot then add ~5L @75C, leave it for ten minutes then drain.

[David Williams]

Have you read much on http://braukaiser.com? His section on wort production covers a good deal including efficency and pH.

[David R]

Haven't seen it before, looks like I've got a lot of reading to do! Thanks.