Split Mashing

[ListerH]

So when I look up splitting the mash on the forums, I tend to read posts about splitting up the overall mash in order to be able to brew big beers (where mash tun capacity is an issue)… but I was actually trying to find a different kind of info.

Here is what I am considering:

I am thinking that if I am generally using my base malts to deliver simple fermentables and using my specialty malts to deliver depth, body and flavor, why do I mash the entire malt bill using the same mash schedule?

What if I do 2 separate mashes, perhaps all of my base malt at lower temperatures and all of the speciality in a second mash at higher temps. Then combine the 2 worts for boiling.

The only drawback that I can really see is the amount of time this is all going to take... but is there anything else that I am overlooking?

I'm always up for a bit of an experiment!

 

[IslandLizard]

Sure, there are many ways to mash.

Some brewers cap their mash with the recipe's specialty, roasted, crystal malts, etc. after the mash, right before (fly) sparging, which may take as long as an hour.
This method will probably work with batch sparging as well, as long as the "capped malt" is given enough time to thoroughly hydrate, gelatinize, and extract/dissolve all sugars, caramels, and other flavor and color compounds.

Others leave the dark and roasted malts out and steep them on the side to reduce potential astringency. I take that a step farther by not adding the steeped black potion until after the boil, at around 155-150F for 5' to pasteurize. I think it helps keeping the roasted flavors fresher, cleaner, while reducing astringency and cooked coffee flavors and aromas.

Most starchy specialty malts benefit from having a diastatic malt present to extract and convert fermentables, keep that in mind if you separate them out. The average diastatic power (DP) of any grist should be above 35 °Lintner for complete conversion. Mind, at such low level, additional mash time may be beneficial. Do an Iodine test to verify all starches have been converted.

Due to their inherent acidity, specialty, roasted, and crystal malts help bring the mash pH down to the proper range. If you leave them out you'll need to add (additional) acids to compensate. Use a mash/sparge water calculator like Bru'nwater or Mash Made Easy to calculate your predicted mash pH, as well as mineral and acid additions.