[NOTE: This is a very advanced topic.]
I've wanted, for a long time, to write a procedure for using the BIABacus to partigyle. One main problem is that I generally do not brew high gravity beers ([mention]Sarah[/mention] Sarah has forced me several times) and the grain bill on those done has not lent itself to being re-used for a lower gravity brew e.g. Cherry Chocolate Stout! Since tasting Rocky Ridge's absolutely beautiful Rock Juice, I now have the desire!!!
[mention]lukasfab[/mention] and I will brew it on Sunday week. Ricky from Rocky Ridge has already given Sarah a few tips and she'll drop in this Sunday to help with the recipe design. (She can't brew with Lukas and I as she's working ).
What is Partigyle Brewing? (Very Brief)
I'll use SVA (Single-Vessel All-Grain), i.e. pure BIAB, as the method although the same principles apply for MVA (Multi-Vessel All-Grain). When brewing high gravity beers, a lot of sugar remains in the spent grain. Partigyle started in days of yore to utilise this sugar, a second batch of beer was made from the left-overs of the first batch.
Think of it like this... clean a filthy bath towel in a 5 gallon bucket of water. Lift the towel out, give it a bit of a twist and then dump it in another 5 gallon bucket. Pull the towel out of the second bucket, give it a bit of a twist and then throw it on the floor. What you'll note are the following...
The first bucket of water will be really dirty and there will be a bit less in it because the towel soaked up some of the water and retained it.
The second bucket will be cleaner but will still be dirty and there will be more of it because the towel was already wet when dropped in the second bucket.
In the above analogy, we can think of the dirt as being sugar. The first batch yields very sugary water (high gravity sweet liquor) while the second yields a much lower gravity.
There are many ways we can play around with our dirty towel and buckets. For example, what if we put the dirty towel in a 10 gallon bucket first and then put it in a 5 gallon bucket. Would both buckets be left with equally dirty water? Or, what about the opposite?
Old hands here know that the BIABacus is the first and only software that auto-estimates kettle efficiency. The existing algorithm is pretty good however it is a linear one whereas, in reality, at extremes, kettle efficiency changes rapidly. For example, put a dirty towel in 1 gallon of water, clean it and pull it out. What is left? A few dribbles of very dirty water. So, you have had almost zero efficiency in cleaning that towel. Put a dirty towel in 50 gallons of water and it is going to be pretty much as clean as if you had washed it in 200 gallons. Anyway until a mathematician puts their hand up we need to stick with our linear formula which does seem to be working really well.
Thinking through the Partigyle Plan
Assuming you have come up with a grain bill that will work for both a high and low gravity beer (e'g' an IPA and an APA) the first thing to decide is which batch do you want to give priority too. There are three choices:
1. Aim for a full fermenter of the high gravity brew and get what you can for the low gravity brew.
2. Aim for a full fermenter of the high gravity brew and get what you can for the low gravity brew.
3. Play around with the BIABacus to find a compromise.
In the next posts, I'll explore the first options on how, using the same grain bill, I plan to brew:
- An Imperial New England IPA (9%ABV)
- An American Pale Ale (4.5%ABV)
Post #1 made 7 months ago
Last edited by Pat on 18 May 2018, 15:29, edited 3 times in total.
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