Split batch behaving badly

[bowler]

Hi guys,

Let me begin with a bit of background.

I had a bunch of leftover grain and loads of hops, so I decided to make a hop comparison batch, in which I make one normal (21-25L) batch, then split it into five smaller batches.

Each of these smaller batches I then boiled with a single strain of hops, with two additions and totalling about the same number of IBUs, so as to compare the flavour rather than bitterness.

Each of these mini boils has been done in exactly the same way, using exactly the same equipment, and even at almost the same time of evening.

But something strange is happening: each wort is coming out with a progressively higher post-boil gravity. The first one was 1.058, the second was 1.068, and the third was 1.075.

I'm measuring them with the same refractometer, calibrated against distilled water.

Can anyone explain what might be going on? It's got me stumped...

 

[Jogurt]

Well are you sure you mixed the wort well after lautering and before splitting into 5? By well I mean really well.
I do not suppose you tasted the 5 different worts pre-boil? That might help in telling if it was the same.

However if what you say is true, the more important question is what to do now.
With the same equipment, the same boil time and the same volume under the same circumstances, you must have had the same boil-off. And the different post-boil gravities imply that you had different pre-boil gravities, therefore different worts.

Now if you carry on with the experiment, the different worts will probably still showcase the individual hops. Just with a different malt backbone. And "different" might mean slightly different, but also beyond comparison.

Personally, I would mix all of the small batches back together to create a unique albeit probably unrepeatable project. It will end up as a good beer, if no mistakes were made elsewhere.
If you carry on with your former plan, the outcome is uncertain to say the least.

These are my opinions, I did not encounter the same problem in my brewing, so others might have more to add.

 

[bowler]

I forgot to mention, I've been no chilling recently, so before I split the batch up and put it in its little cubes I boiled it for 15 minutes or so to sanitise it. That should have mixed it up pretty thoroughly, I would have thought.

I'll think about mixing them back together again, but I feel like they'll demonstrate what I wanted them to reasonably well.

 

[Zepth]

I tried this a little earlier on in my brewing, and promptly ended up having my second batch mashing for a couple of hours while boiling the first. That's the type of mistake a guy only makes once. End result is enjoyable just not the scientific experiment I was hoping for.