How do I calculate a turbid mash schedule?

I'll use a real life recipe for my lambic that I've been brewing over the years to allow for an answer that posts both the methodology and mathematics while also providing the calculated quantities I would need to follow for my recipe.

For my lambic recipe:

• Batch size: 11 gallons
• Est. Efficiency: 85%
• Est. Original Gravity: 1.054
• Boil Time 120 minutes
• Boil Loss: 1 gallon/hour

For the grains, nothing too out of the ordinary (yes, only a quarter of it is wheat):

• Belgian Pilsner (75%) ~ 14lbs 8oz
• Torrified Wheat (25%) ~ 4lbs 13oz

How do I take the above stats for my lambic and perform a turbid mash? What are the steps that need to be taken, at what temperatures, and with what amounts of water?

• Here's a good article on the subject. I haven't done this, but I have done decoctions, this doesn't sound too bad. It seems like two burners are required, one for hot liquor and one for the removed wort.
– Pepi
Commented Apr 2, 2015 at 14:21

Here is the 'method' section on turbid mashing extracted from the same article Pepi references above:

"Your turbid mash begins in a manner similar to a regular infusion step mash, albeit much thicker. Dough in to 113 °F (45 °C). Your liquor to grist ratio at this point will be around 0.3 qt./lb. (~0.7 L/kg). Bring the water in the hot liquor tank (HLT) to a boil and, after the mash has rested 10 minutes, raise the temperature to 138 °F (59 °C) by stirring in boiling water. This should bring the mash to an overall thickness around 0.45 qt./lb. (~1 L/kg). Hold for 5 minutes at this rest.

At this point, the unusual aspects of the turbid mash begin. Draw off about 1 qt. (1 L) of turbid wort (if brewing a 5-gallon/19-L batch of beer). Do this by sinking your colander into the mash and scooping or siphoning off the wort. An auto-siphon comes in handy for this. Do not collect any grain solids in this volume. (Skim them out with a strainer, if your colander lets some solid bits through.)

Place the turbid wort in your small pot and heat it. An easy way to do this is to float the small pot in the boiling water in your hot liquor tank. You want the turbid portion to reach at least 180 °F (82 °C).

Now, stir in more boiling water to raise the temperature to 150 °F (66 °C). Hold at this temperature for 30 minutes, stirring often. The mash will still be thick, so you’ll have to work fairly hard at this.

Next, it’s time to use the colander again. This time, the mash is a bit thinner — although still thicker than a normal mash — and you will collect about a gallon (3.8 L) of wort (again assuming you are brewing 5-gallons/19-L). Combine the wort you draw off with the first turbid wort in the small pot. Heat this portion as before, aiming to raise it to at least 180 °F (82 °C). For the final mash rest, stir in boiling water to raise the temperature to 162 °F (72 °C) and rest for 20 minutes. While waiting to lauter, add water or otherwise cool the water in the HLT to 190 °F (88 °C).

Collecting the wort involves some unusual steps compared with normal wort collection procedures. First drain off some of the wort to the kettle — roughly the same volume that you have contained in your small pot. Replace the wort you ran off with the wort in the small pot. This should bring the mash temperature to 167 °F (75 °C). Hold for 20 minutes, then vorlauf and run off the rest of the wort, sparging with 190 °F (88 °C) water from the hot liquor tank.

From my experience with utilizing a turbid mash there are a few pointers to keep in mind to assure success when following the procedure laid out:

1. Before starting, make sure your stuykmanden (colander) fits in the mash tun

2. Make sure that, by pressing down with the colander, you won’t be bending any temperature probes or crushing any screens or manifolds.

3. Adding 0.5–1 lb. (0.23–0.45 kg) of rice hulls to the mash during the saccharification rest is a smart choice when using unmalted wheat. This is an added buffer to assure against a stuck sparge.

My research into making an authentic kriek led me into the realm of the turbid mash and eventually into this article. Hopefully it will lead some brewers - especially those who are “Belgian-inspired” - to try this interesting and authentic method of mashing."

http://byo.com/hops/item/1711-turbid-mashing