Single Mash 5 gallon to 4 smaller boils?

It'll fly but:
1. it's a lot of work
2. you're likely to get less finished beer due to racking from 4 separate fermentors instead of 1.

 

I would absolutely do that as long as you have appropriately sized vessels to ferment in. You wouldn't want to ferment a 1.25 gallon batch in a 5 gallon bucket because of all of the headspace... but if you have a few 2 gallon jugs (or something similar), I think this would be a killer experiment.

Regarding the starter, just do your best to pour equal amounts of yeast into each vessel. This is harder to do than it sounds because each layer (trub, krausen, etc) has different concentrations of viable yeast cells. Make sure it is good and mixed up before pouring equal volumes of slurry into each vessel.

Sounds like a great experiment! Keep us posted on your findings.

 

To add to what @mugs1789 stated, it does work and is great for experimenting with hop profiles, but it's so much work and there are 4 chances now of getting something wrong. Also smaller batches will react differently so be careful and understand scaling up and how much faster things work in smaller batches.

But I'm sure you got this. Have fun with it and let us know how it goes!!

 

Triskel and Strisselspalt ?

 

One other variable to keep in mind is your boil off rate. 4x the boiling will result in 4x the boil off, assuming the same kettle is used for all 4. If you're using smaller kettles, you'll boil off less than 4x, but you also may end up with a stronger boil than usual.

 

Recommend that he gets a gallon or two of RO or distilled water that he can add back during the boil if he sees he is getting too much boil off.

 

Are you testing for bittering qualities, flavor, or aromatics? If predominantly aromatics, I'd boil the wort together with a neutral bittering hop, split it into 4 different fermenters and dry hop with the different hops in said fermenters.

 

How are you going to package the beers? Bottling buckets seem to end up with more than a couple ounces in the bottom. That doesn't matter for a 5 gallon batch, but could be really painful for four 1 gallon batches. One of my worst bottling days was when I had to package 5 gallons of RIS that I split 4 ways (bourbon, coffee, oak, plain). Even when I did not care about a little bit of mixing so I did not clean the bottling bucket after each batch, it was still a huge pain to rack such small amounts to the bottling bucket. It felt like Groundhog day, I just kept doing the same shit over and over

Based on experiments with different yeasts in the same beer, the smallest batch I would be willing to bottle would be in the 2.5 - 3 gallon range.

 

I am going to disagree with this statement. Until recently I always brewed 3, 3 1/2 gallon batches and fermented in a 7+ gallon speidel fermenter (it's a 30L to be exact), and never had any problems with headspace. If it's being racked in a secondary the headspace would be an issue.

 

^^^ This. I just made two IPAs from one wort. I added a couple quarts of distilled water to each batch to account for the greater loss of volume from doing two boils instead of just one. Going 4 ways, you might need to add an entire gallon of distilled to each batch! Trust me though, this will work out great in the end.