Is there a reason not to add wort late like we add sugars late?

[FatherDougal]

I am wondering if, since people often add sugar to a ferment after it is going, sometimes in multiple steps, is there are reason that people don't add extra wort to a ferment once it gets going? Does it fail in some way, or is it not done because nobody ever tried or thought about it? In a way it seems like just doing a big starter.

I can see two uses. First, I have to do all grain on my stove, which means small batches. But, I could do a 2 gallon batch one day, top it up to 3.5 gallons and than another 1.75 gallon batch later and add it to the already going ferment. That way I get a 5.25 gallon all grain batch.

The other would be for higher gravity, where I start a 3 gallon batch at 1.050 and then add three batches of .75 gallons with 3.3lbs of LME each to end up with a 5.25 gallon batch at 1.095. Would presumably be much easier on the yeast.

Would love to hear people's thoughts. Has anyone ever tried this?

 

[Kharnynb]

outside of a higher chance of infection, i'm not sure it would do much for yeast viability, which tends to be more about alcohol %

 

[Sadu]

I had to do this yesterday. 24 liter batch ended up at 27 liters which is cutting it fine in a 30 liter fermentor. So I reserved a growler of wort and added it on day 2 once I had a handle on how vigorous the fermentation was looking. Definitely a small infection risk doing it this way but if you are doing a fresh boil on the day I can't see any issues other than the extra work required in 3 brewdays to get one batch of beer.