Where do I start? I brew 10 gallon batches, so if I wanted to brew an IPA then add some roasted malt to the mash tun and then brew 5 gallons of stout could this be done? I would I calculate the SG of the stout?
So IPA grain bill is 12lbs of 2row, 8lbs of munich II, 6lbs of rye, 1lb of crystal 40 and 1lb of crystal 60.
I don’t think an IPA is a good candidate for a parti-gyle. The second runnings will have a very low gravity. If you are planning on doing a double IPA then you are in the ballpark, but you might need some malt extract anyway.
Do you batch or fly sparge? If batch check out sean terrills partigyle simulator as a starting place. If fly check this article and associated tables out to help with the math
(which hamilton already linked to)
I don’t know that you would get a stout perse with that recipe but you will get a dark beer and it will probably be tasty.
basically you do whatever mash you want for the IPA making sure you end up with your whole first runnings volume in the tun.
Toss the roasted grain in, stir and let it sit for 10-20 minutes and then run off again.
I only have the one burner so I usually do a mash out step, run off my first runnings into a bucket or spare kettle then do the second mash and boil that first because I want to stop conversion on the smaller beer ASAP. If you have two burners you can boil at the same time.
I’m planning a partigyle starting with a Barleywine then a session Brown to follow. I like to start with a strong ale followed by a session style for this method to get the most bang for the buck.
I’ve used Kai’s Batch Sparge and Parti gyle Simulator many times and it is very useful for predicting your gravity for a parti gyle, if you know your conversion efficiency. If you don’t know your conversion efficiency, but know the sparge volumes and gravity from a previous batch, you can use it to reverse calculate your probable conversion efficiency, allowing you to use it predictively.
On brewday, you can use the gravity of the first beer runnings to calculate the exact gravity of the second. Since you know how much water is held up in the grain and the gravity of the wort, you can easily divide that gravity by the total volume of that wort and whatever water you wish to add. Adjust that added volume until you calculate the gravity you want for the second beer, then add that volume to your tun. The collected volume will be whatever you add, of course, so you might find you have to either make a smaller volume of beer than you intended or go with a lower gravity. Make sure you adjust the hops accordingly.
I think this is probably true if you try to make 5 gallons with just the second runnings, but you might be able to get 3 gallons of a low gravity stout.
Another option is to make a gallon or two extra of the first wort and add it to 4-5 gallons of second runnings, to bump up the second running gravity. This is basically how the Fuller’s brewery makes their moderate gravity beers.