What's going on?

[PaulStat]

Morning folks,

I did another brew last night which I thought went pretty well, but I was aiming for an OG of 1037 and my hydrometer tells me it's 1030 (measured @ 20C). I don't know why either? The last few brews I seem to be missing the OG by a good few points, so I'm suspecting the hydrometer is no longer accurate? Anyway here's the details

25L brew length Est OG 1037 IBU 27

3480gms Maris Otter
395gms Crystal Malt 60L
80gms Wheat Malt

45gms EKG 4.6% 90 min boil
25gms EKG 4.6% 15 min boil
10gms EKG 4.6% <80C steep

Mash volume: 10L
Top up volume: 12.3L
Batch 2 volume: 17.1L

Now one mistake I do know of is that I forgot to take into account that the dead space in mash tun has reduced from 1.2L to 800ml, but that's probably not going to make much difference.

It took me 28 minutes from turning the boiler on to getting the grain in the mash tun and for it to be mashing. It was then left for 90minutes starting of at 66C, at the end of the 90minutes it had dropped to about 62/63C.

I batch sparge, nothing out of the ordinary here I used the same method I always do. Top up, stir, leave for 10 minutes, collect runnings, rinse. Add batch2, stir, leave for 10 minutes, collect runnings, rinse.

3hr 23minutes after starting I had a rolling boil going, I can't fit all the liquid in the boiler at once so what's left over is left in the vat until enough has boiled off. Once enough had boiled off I added the rest, this of course stops the boil, and takes roughly 5-10 minutes to get back up to temperature. I took this into account and extended the boil by 10 minutes.

After the boil I turned on the IC, it's taking longer these days for some reason, when I started back in October it was taking 25 minutes to cool, now it's taking 40 minutes to cool. Water coming out of the tap warmer this time of year?

After 6hrs start to finish I had collected my 25L of wort and pitched the yeast. But my hydrometer tells me it's 1030 and not the 1037. I don't understand?

Thanks,
Paul

 

[albannach]

If you suspect that your hydrometer might be off, check this out: http://www.honeycreek.us/hydrocal.php

Also, your brewhouse may just have a lower conversion efficiency than you think; check your hydrometer first though.

 

[PaulStat]

Blimey, that's a very detailed guide!

One thought, when I've cooled the wort I collect the first 80ml or so in my trial jar and then measure the OG of that. The first 30ml or so of that is always really dark (I wouldn't want to drink it), I presume because it's been sitting in the closed pipe collecting the crap throughout the boil. Is it possible that this first bit of wort is mis representative of the rest?

 

[albannach]

If you mean that it has been sitting in the ball valve in your boil kettle, then I guess it's possible that flame/heat coming up the side of the kettle could be scorching that insignificant amount of wort. But conceptually, I don't think it would affect your SG reading. Even though they are burnt sugars, they are still sugar, and would have the same effect on SG as regular sugar. Someone please correct me if you know for a fact that I am wrong.