Double mash full grain for 120 minutes?

[gokcenami]

I came up with an idea to raise my efficiency a bit, using BIAB method.

What if I mash for 60 minutes with regular grain/water ratio, then instead of sparging, empty the mash tun and refill with the same amount of water and mash out after another 60 minutes? Then squeeze the heck out of the bag and start my boil?

Will I get a higher SG with this method?

 

[RPh_Guy]

I do that. It's called a "batch sparge". It does increase efficiency over no sparge.
60 minutes for the sparge is unnecessarily long. 5-10 minutes is plenty.

... What efficiency are you getting? Anything 65%+ is pretty reasonable in my opinion.

 

[mullet6577]

I'm pretty sure that is still considered a "sparge" and wouldn't need to be done for another 60 minutes since most of the conversion has already happened.

edit: ^^^^^just a little faster than my reply

 

[gokcenami]

@mullet6577 OK thanks! So I will do it for 10 minutes then. My efficiency is around 66%. Problem is my boil kettle which I use as a mash tun as well, is small so I need to add water after for boil-off in order to get my desired batch volume. The water addition lowers the gravity so I felt like I need to raise my efficiency a bit.

 

[madscientist451]

What if I mash for 60 minutes with regular grain/water ratio, then instead of sparging, empty the mash tun and refill with the same amount of water and mash out after another 60 minutes? Then squeeze the heck out of the bag and start my boil?

Will I get a higher SG with this method?

So the question is: Does letting the batch sparge water sit on the grain for 60 minutes result in more extraction of fermentable sugars?
I'm going to say no, it won't help, but how about trying an experiment: brew the same batch twice, using the 60 minute sparge and then re-brewing with just a simple rinse sparge.

 

[RM-MN]

The real answer is, "it may". If you are getting a brewhouse efficiency of 66% your grains are crushed too coarsely and you probably aren't getting full conversion in the 60 minute mash. You could continue the mash longer to get more conversion without draining the mash tun and refilling it. However, there is a practical limit to this. A 90 minute mash is probably about the limit.

When you drain the mash tun and fill it with water of the proper temperature it will do similarly if the conversion isn't complete, allowing more starches to convert, but the major thing is rinsing off more sugars from the grain. For rinsing the sugars, the water temperature isn't very critical. Please note that with BIAB and any other method of mashing and sparging a mash out isn't needed. It is only needed for fly sparging and then only if conversion isn't complete.