Also see the easier turbid mash suggestion below.
Traditionally the mashing is carried out by mashing in and then removing the liquid portion and boiling it and at the same time adding boiling water back to the mash to raise the temperature. This procedure of removing the turbid liquid, boiling it and adding boiling water to the mash is carried out for a number of times until the mash reaches a temperature at which the addition of the boiled turbid runnings raises it to saccharification temperature. After a 2 hour sacharification the wort is run off and the grains sparged with close-to-boiling water. Again this whole procedure helps break down the ungelatinized wheat giving one a wort high in amino acids, dextrins and starches. The whole process is followed by a 4 to 5 hour boil to reduce the large volume of liquid and precipitate the excess proteins and burst any starch granules.
Here is Mike Sharp's description of Cantillion's turbid mash:
Malt - 850Kg Wheat - 450Kg | ~8-900 liters | H2O @ 62C -->It takes 15 to 20 min. to mix all the grain and H2O. This results in mash temperature of 45C. | mash held at 45C for 10 min. | H2O @ 100C -->In ~6 min. enough H2O is added to bring the mash to 58C | In ~5 min. ~300L is transferred to kettle #2 ---------------->| | ~300L in kettle #2 H2O @ 100C -->In ~10 min. enough H2O is heated. during is added to bring the the heating it never mash to 65C reaches 100C | | In ~35 min. ~1200L is | transferred to kettle #2 ---------------->| | an additional ~1200L H2O @ 100C -->In ~10 min. enough H2O is added to kettle #2 is added to bring the and the heating of this mash to 72C kettle continues. it | never reaches 100C mash held at 72C for | 20 min. | | | +----> first runnings (~1500L) | to kettle #1. begin | heating of this kettle | for the boil | | transfer the contents of kettle #2 back to |<-------------------------the mash tun. At this | time the contents of the mash is now this kettle has reached at ~75C ~80C | mash held at 75C for 20 min. | recirculate the wort in the mash tun to clarify. | sparge with 85C H2O | split wort between the two kettles as it runs off. kettle #1 will contain ~6500L total (including the 1500L previously put there) kettle #2 will contain ~3250L total. | add 21KG aged hops to kettle #1 only. heat both kettles to boiling and allow the volume to be reduced by ~25% to yield a full batch size of 7500L total between the two kettles. The contents of the two kettles are blended together before cooling overnight.Mike has this to say about this turbid mash:
This particular mash technique is unique to lambic breweries. No other style of beer involves this particular mashing process. Though it is not used by all of the lambic brewers, it is in use at the majority of the remaining lambic breweries. Among the brewers there are mixed feelings as to the need for this process. At Brasserie Cantillon, Brouwerij De Troch, and Brouwerij Boon it is used because that is the way it has always been done. At Brouwerij Belle-Vue they use a substantially different technique which I will cover in my article on that brewery. Much later in my trip, during a discussion with Professor Verachtert of the Katholieke Universiteit du Leuven, it was suggested that this particular process lends little to the brewing of lambic and the results of the Belle-Vue process would tend to support this.This post is from Lambic Digest #603
Note that the yield of this mash is 33-34 pts/lb/gallon. Initial homebrew attempts suggest that your yield may be more like 25. You may wish to increase the grain bill accordingly.
An easier turbid mashing method comes from a suggestion by Frank Boon. He suggests mashing in at around 86°F using as little as 1 quart of water per pound of grist. The mash should then be stirred and the milky wort should be run off and boiled for a few minutes. In the mean time fresh water should be added to the grist and a step mash performed of ones choosing. After reaching the 140°F range the boiled milky wort is added back to the mash to raise the temperature to the sacharification range. Then the mash should be allowed to rest and undergo sacharification. After this the wort should be run off and the grain sparged. This produces a large volume of liquid and is one of the reasons for the suggested 5 hour boil.
Be aware that you will probably not get complete starch conversion in a mash with raw wheat regardless of how rigorous a mash schedule you use. This is not a problem, however, since you want a certain amount of unconverted starch to carry over into the wort to provide a substrate for the Brettanomycesto feed upon late in the fermentation and maturation.
The sparging of a lambic mash is typically carried out with water that is hotter than 165°F, usually closer to 190°F. This aids in extracting dextrins and unconverted starches from the mash. This procedure also extracts tannins from the malt as well, but these are precipitated out over the long fermentation cycle and do not contribute to astringency in any large part. The use of hotter-than-normal sparge water is particularly important if one follows a true turbid mash type schedule due to the poor conversion. In normal beer production one does not want all of these various components extracted into the wort but in lambic brewing they are needed to support the long fermentation process and will ultimately be utilized by the yeast and bacteria. Without these usually undesirable products the lambic organisms will not thrive and produce an optimal product.
There is some variation in the way lambic, particularly gueuze, is bottled in Belgium today. Many of the brewers artificially carbonate and/or pasteurize their beer to produce a more consistent, less aggressive product that has a wider market appeal. In their beers the ratio of old to young beer or top fermented ale is typically not very high. The more traditional brewers who make true, refermented gueuze also use various ratios of young to old lambic, but never use normal top fermented beer. The method used by some involves the mixing of 50% two-year-old or older lambic with 50% young lambic of 6 to 12 months of age. The beer is then bottled and allowed to referment in the bottle for up to two years prior to release. The method favored by Boon involves mixing 95% 2 year old lambic with 5% 2-3 month old lambic and then bottling. He prefers this method due to the fact that the 50/50 method can lead to ropy and or hazy bottles that do not develop a consistent character. This is not brewing art in his opinion.
We plambic brewers rarely have the luxury of being able to mix young and old beer, so we have to make due with what works for our other brewing, that is using priming sugar of some sort. Of course if you do happen to have lambic-style ales of various ages fermenting then by all means go ahead and try to blend and bottle them and see what you end up with. Gueuze, being refermented in the bottle, is fairly highly carbonated, although some examples of Cantillion are nearly flat. This is probably due to the cork's allowing the CO2 to escape overtime.
One problem with bottle conditioning a beer that has been fermenting so long is that the number of viable carbon dioxide-producing organisms may be very low. If this is the case the beer may not become carbonated or only very lightly so. To combat this problem you may want to prepare a fresh starter of Brettanomyces and/or Saccharomyces at the time of bottling. Then you want to prime with enough sugar to end up with a fairly carbonated product. One cup of corn sugar in 5 gallons followed by about two months of bottle aging seems to give a fairly high level.
One might worry that it is not a good idea to add sacharomyces at the time of bottling since they do not survive through the lambic fermentation process. But those of us who have looked at what is in the sediment of a Boon lambic have discovered that the only yeast generally recoverable is indeed non-cyloheximide resistant yeast, most likely Saccharomyces. Boon fines his old lambic before adding the young beer. Saccharomyces is probably the dominant strain of the young beer and consequently an appropriate addition at bottling.