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Efficiency issue

There are numerous factors that could be at play here.

[list type=decimal]
[*]mill:  this has been covered already.  you may want to try it with already crushed grain - just to make sure and eliminate causes.
[*]quality of the grain:  if your grain wasn't stored correctly it will lose diastatic power rapidly
[*]mash schedule:  not your strike but your actual target temperature should really be 65 Celsius.  You can do other things to affect conversion efficiency.  Ie step mashing.  Dough in with a thick ratio (1:2) at 35Celsius, then raise to 65Celsius after 15-30 minutes.  You could also take 1/3 of the grain and boil it for 5-10 minutes.  This will certainly release more starches and improve your efficiency.
[*]sparging:  incorrect sparging can lead to huge efficiency losses.  it is important not to create too much suction and compress the grain bed too much.  this will have huge impacts on efficiency.  try a lower flow-rate if necessary
[*]pH:  pH can have a far more dramatic effect on the end-result than temperature.  Ensure your mash is in the pH 5.3-5.6 range.
[/list]

Hope this helps ;)
 
cheers. I'll look at those things for next time. Much appreciated.

PS[edit]: After the boil and into the fermenter/s OG=1038
 
There are numerous factors that could be at play here.

[list type=decimal]
[*]mill: this has been covered already. you may want to try it with already crushed grain - just to make sure and eliminate causes.
[*]quality of the grain: if your grain wasn't stored correctly it will lose diastatic power rapidly
[*]mash schedule: not your strike but your actual target temperature should really be 65 Celsius. You can do other things to affect conversion efficiency. Ie step mashing. Dough in with a thick ratio (1:2) at 35Celsius, then raise to 65Celsius after 15-30 minutes. You could also take 1/3 of the grain and boil it for 5-10 minutes. This will certainly release more starches and improve your efficiency.
[*]sparging: incorrect sparging can lead to huge efficiency losses. it is important not to create too much suction and compress the grain bed too much. this will have huge impacts on efficiency. try a lower flow-rate if necessary
[*]pH: pH can have a far more dramatic effect on the end-result than temperature. Ensure your mash is in the pH 5.3-5.6 range.
[/list]

Hope this helps ;)
I'd say that the number one culprit is incorrect sparging. The worst fault there is chanelling. Compressing the grain bed will ultimately lead to a stuck mash, but not necessarily to bad efficiency. I've seen that many people brewing on compact systems get chanelling because they can't control the flow like you do on trad systems. You need to have some wort above the malt bed, you need to let the wort flow through the malt bed slowly and evenly, and you need to add aparge water in a gentle way so that it doesn't disturb the malt bed. If you can't do that, batch sparging is a good solution. It gets pretty close to fly sparging efficiencyvise. (I only do batch sparging, and get very good efficiency, with some beers more than 90%.)

You can get dramatically decreased efficiency if your crush is too coarse. But that takes a lot and is rare. But I have seen it happen. Within a normal range of crushes, though, the effect is not large.

I disagree about the importance of pH. It does matter, but not much. To get hung up on a narrow target there won't do you much good. (I own a good pH-meter and am addicted to it. But I don't panic if I don't hit my target.)

The old acid rest should be avoided because you're likely to get oxidation of long-chain fatty acids by the enzyme lipoxygenase. How much that will affect the finished beer is a matter of discussion, but I really don't see the point. You might perhaps get a point extra, but ... . To put it bluntly: When using modern malts there is no reason why you should not mash in directly at the saccharification rest. (OK, you may do some veird things to increase fermentability, or produce extra banana flavour in a hefeweissen, but that doesn't belong here.)

The effect of mash thickness is minimal. A very thich mash will lower efficiency, but you would only do that in rare cases.

Boiling the mash to gelatinize more starches will give little effect. I've tried, and it didn't work. The gain should be there, theoretically, but with modern malts it is at best marginal. (Decoction may - or may not:) - have an effect when it comes to taste, but it's completeløy meaningless as a means to increase efficiency when you use modern malts.)

I've seen a lot of discussions over the years about efficiency problems posted on our Norwegian forum - the forum of the Norwegian Homebrewers Association - and 90% of them have clearly been related to sparging. Conversion is easy. You mix water at the right temperature with malt, and you keep it there for a certain time, and you need to do some pretty gross blunders not to get close to 100%. Sparging, on the other hand, is where you can go wrong. So that's where to put your focus if you get lousy efficiency.

One caveat, though: Continous circulation may lead to chanelling. It's suåpposed to be great to keep an even temperature in the mash - which isn't all that importnat - but it may cause efficiency problems.
 
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