This week I take a look at some of the key process factors when lautering and sparging your all Grain beer. Last week in part one, I discussed equipment design and how a filter bed forms around grain husks and creates channels that the wort flows through. I explained why a poorly designed lauter tun can create large channels that hurt your mash and brewhouse efficiency.

Process Considerations for Lautering

Probably the most important process step in establishing a good Grain Bed is the quality of the grain crush. When brewers come to me asking about low mash and brewhouse efficiency, the first question I will ask them is how they crushed their grains.

As I mentioned earlier, properly crushed malt leave a large portion of the grain husk intact and those husks form a filter bed that allows sugars to be extracted from the bulk of the crushed malt without gumming up the bed and creating a stuck sparge.

A two roller grain mill is ideal for crushing your grains as it leaves large pieces of hull intact. However the gap on your mill must be carefully set so it crushes the interior of the malt to a fairly fine powder without destroying the husk.

A note of caution that not all brewing supply shops carefully set their mills, and the mills they use face high volumes, so purchasing pre-crushed grains can sometimes not result in a high quality crush. Also in some cases certain specialty malts require slightly different gap settings to get the best crush.

The second major consideration when mashing and sparging is to get your volumes correct. The volume of water used in the sparge is driven mainly by your desired pre-boil volume. However you need to also take into account the water already in the mash and also volume absorbed and trapped by the grain itself. Most systems also have some deadspace below the lautering filter, so additional losses must be accounted for there.

Starting with the water you add to your mash itself, you must first remove grain absorption which runs about 1 liter/kg (0.96 pts/lb) on average. Brew-in-a-bag (BIAB) systems achieve more compression in a grain bag and typically run about 0.4 to 0.5 liters/kg, or roughly half as much as a regular mash tun, though obviously you do not complete a lauter step with the BIAB system.

Subtracting grain absorption from the water used to mash in, we get the approximate volume of water already in the mash tun before lautering. Next we simply take the desired pre-boil volume and subtract the water absorbed by the grain to determine the lauter volume needed. We also need to add a bit more for losses in the lauter tun, such as any unrecoverable volume below the mash tun filter. This final number will tell us how much water to sparge with.

Lautering Temperatures and the Mash Out

Next we need to determine what temperature to heat our sparge water to, and also whether to use a mash-out step.

A mash-out step at a temperature of 168F (75.6 C) or so was traditionally included to “stop” the enzymes during the mash which was thought to help control the conversion process. In reality the enzymes don’t stop at that point but are converting at a much slower level. Now, a mash-out is primarily done to increase the viscosity of the wort to aid its flow through the grain bed.

I personally don’t do a mash-out much anymore unless I’m working with a high percentage of sticky adjuncts like oats or wheat. With a properly designed system and proper grain crush, most barley based beers simply don’t require a mash-out.

You may also find older references that say using hot mash water (above 180 F or 82 C) can result in tannin extraction during the mash. This is not correct. Excess tannin extraction is typically caused by pH problems (see below) in the mash and not simple raising the temperature of the bed too high.

I personally run my lauter/sparge water at about 178F (81 C)as this will raise the temperature of the grain bed and increase viscosity without causing problems.

Lautering Time

Given that lautering is primarily a diffusion process, and not a rinsing process you should lauter your grains slowly. Giving the water time in contact with the grains will result in better extraction and a higher original gravity. I typically take a minimum of 20-30 minutes to lauter my grains, and sometimes take longer. You also want to manage the inflow and outflow of the lauter process to maintain a “floating grain bed” and not compact the grains during lautering.

Lautering pH

While the subject of mash pH is a complex one I’ve covered before, intermediate and advanced brewers should be using acid of some kind to manage their mash pH during the main conversion mash step. In addition to this, professional brewers also monitor the pH of their runnings. As you flush more alkaline water through your acidic grain bed, the pH of the runnings will rise. So the wort coming out of the grain bed will slowly increase in pH. The rule of thumb is to not allow the pH of your runnings to go above the 6.0 level, as pH readings higher than 6 are associated with high tannin extraction. Too many tannins (a flavor akin to sucking on a tea bag) is not desirable in your beer. Depending on your starting mash pH this can be a problem particularly for lower gravity beers.

Vourlauf and Recirculation

Most brewers start their lautering process by doing a vourlauf where a few quarts of the first runnings from the mash tun are collected and added back to the top of the mash tun. This gives your grain bed time to set into a good filter structure, and also reduces the amount of debris in the finished wort.

In addition many newer homebrew systems have a recirculation pump that continuously recirculates and sometimes heats the wort during the mash. Recirculation generally results in clearer wort as it allows the grain bed to settle before lautering. The only downside is that recirculation can set up channels in the grain bed that bypass some of the grain. This is particularly the case when your recirculation returns the wort to a single point on top rather than distributing it across the grain bed, so you need to consider not only the wort being pulled form the bottom, usually through your filter, but also where its going back in at the top.

Lautering appears to be a simple process at first, but a deeper dive demonstrates that there are some significant issues to consider in both equipment design and process when lautering your grains. I hope you enjoyed this week’s article from the BeerSmith Home Brewing Blog. Please subscribe for regular weekly delivery, and don’t hesitate to retweet, link, like or mention any of my articles on social media.