We wish to brew 10 gallons of Barleywine. My mash tun will only hold enough grain to do a 5 gallon batch.
Is there any work around to get a 10 gallon brew? Would using a malt extract work?
Or do we need to plan on doing two separate 5 gallon brews?
I would do 2 separate 5 gallon batches.
Remember that for big beers like that, efficiency usually goes way down - so account for that.
Sometimes you need to boil for 2 hours as well because of the extra volume needed to get a decent efficiency. I do on my system at least.
Back in my extract days, I made a barleywine that was extract based and it involved a 3 gallon boil and top up water at end of boil to get to 5 gallons, so I would think that you could do it any number of ways: 1) with 2 five gallon batches made end to end or 2) 10 gallons made weaker and then adjust upward with DME at some point in the boil (but the flavor profile would likely be slightly different than the 2 separate batches) or 3) make a 5 gallon (or different volume) batch with a super heavy SG (if the equipment allows it) and add top up water to get to 10 gallons (added to boil or post boil).
All kinds of options!
Probably looking at two separate 5 gallon brews. And one full day of brewing!
I have not made one of these before, and we are looking forward to it.
I used to make 10-12 gal. of BW yearly with a friend. For a long we combined equipment so we’d have enough capacity. I finally bought a 152 qt. cooler that allowed us to do it with one mash with room to spare. Perhaps one of those would be an option for you. We also would get 12-15 gal. of a second runnings beer.
Can your mash tun hold enough grain to brew a 10 gallon batch of a normal gravity beer? If so, you can use an iterated mash to hit your target gravity. Mash, remove grains, then use the wort from your first mash as the liquor for a second mash with the rest of the grain. I do this for 3 gallon batches and it works great. However, I’d imagine that the logistics may make this a lot more challenging for a 10 gallon batch.
The best part is that if you pick the right mash temps you can end up with a very attenuative wort. You can perform your initial mash in the alpha amylase temp range, then hold the second mash in range for a low beta rest that overlaps the range for limit dextrinase. The initial alpha rest provides a lot more substrate for limit dextrinase. This leads to a highly fermentable wort, which is exactly what you want for a big barleywine.
You could also do what fits in your regular tun and do the rest either in a cooler or as a biab then combine in the boil kettle.
Based on past experience, about 30 lbs might max out my mash tun. The most I have put in was 24 lbs. I might squeeze 32 lbs in.
Hopefully, you have a lot of thirsty friends. 
Oh yes, got a few of those. My wife likes the style, so want to brew up something that will be pleasing to her.
Happy wife, happy life.
Personally I would try to borrow a second mash tun if possible. I’d imagine there is at least one other brewer somewhere around you who would help you out.
Good idea.
This essentially what I did until I got a larger one.
Let me run this by you all…
I will mash 24 lbs as usual. Then collect the resulting wort. Dump the spent grain from the mash tun, and add another 24 lbs of grain. Do another mash, but use the wort from the first mash as the hot liquor to sparge the grain.
This would get the 48 lbs mashed (2 X 24 lbs), and I could do the boil (13.5 gallons) in my kettle.
Is this the correct procedure?
There is no one correct answer. If it were me I would use two tuns, probably doing a biab on the side because I wouldn’t want to extend my brewday so much but if you are willing to spend the time this seems like a fine way to go. The only downside I see to what you propose is the possibility of more oxidation.
Look up the reiterative posts by Klickitat Jim. He used to do it quite a bit for high gravity beers. Basically laid out the process from what I remember.
As this is a new experience, I will split a 5 gallon batch with a friend.
Would light Munich Malt fit in the grain bill?
Here is what we have so far:
Pale Malt
Dingemans Special B
Crystal Rosewood 40L
I agree with the others on trying to get another mash tun. I make 5 gallons of Barleywine every year and it maxes out my mash tun around 25 lbs. Also, like someone else mentioned that your efficiency can go down. My usual efficiency is 75-80% and my efficiency for my Barleywine is around 65%.
What OG are you targeting, and are you brewing an American BW or English BW? I’d use caution with Crystal malt in a big beer, especially in an English BW where the hops are less prominent. You can end up with something cloying sweet if you’re not careful.
For Am BW I’d keep it under a pound of Crystal malt for 5 gallons, for English I’d skip it altogether and just use a flavorful base malt like GP or MO. A bit of Munich would be fine in either style, but I’d use a relatively light hand since there is so much malt backbone to begin with.
Target OG 1.107.
This will be an English style, no dry hopping.
The grain bill calls for:
1 1/4 lbs Carastan 34L
1 lb Special B
2 lbs clover honey