How Long Should You Lauter / Sparge?

If you’re looking for a quick answer I will say 60 to 90 minutes. Here’s a little more background for those that are interested. When it comes to the subject of mash efficiency, there are many factors that actually come into play including equipment, mash and sparge water temps, mill setting, time, PH, etc. Most of the new equipment that is on the market is highly efficient and capable of mash efficiency north of 80%. The two things that I look at the closest when I’m trying to squeeze every point of efficiency out of an all grain brew are the crush (mill setting) and the time it takes to lauter. I know that many brewers now prefer to batch sparge as it’s a fast and simple way to get relatively good efficiency. The argument that throwing a few more pounds of grain into the system to save an hour or more is totally valid and I certainly get it. Especially in a commercial brewing environment where time and labor often outweigh the cost of barley. If your grain is properly crushed, a lot of what makes your mash efficient is simply time. Good things come to those who wait! Once there’s water in your mash tun and your starches have converted to sugars, the mash will naturally layer itself with the water (wort) containing the highest sugar content slowly migrating to the bottom due to it’s higher specific gravity. This is why we pump off of the bottom of the mash tun, and why mash tuns typically will either feature a dip tube or a bottom drain… That’s where the good stuff is! If you pull the wort from the bottom of the mash tun too quickly, the higher gravity solution isn’t allowed time to find it’s way to the bottom. The natural layers that should exist in the mash get disturbed mostly due to uneven flow rates through the grain bed caused by excessive flow. I’m certainly no physicist so there’s absolutely no risk of me boring you with a long complex algebra formula for how this all works. What I will share is simply what I have gained from many years of brewing and observation. When I started brewing I was told that you needed to sparge slowly, but no real advice on how slowly. Many years ago, I was brewing in the parking lot of the Dry Dock brewery in Aurora Colorado and the head brewer at the time was Bill Eye. I had an opportunity to ask him about fly sparging and he commented that for 10 gallons or 10,000 gallons it should take 90 minutes. Bill Eye went on to found Bierstadt brewing in Denver and is one of the brewers that I will take advice from any day. Armed with that nugget of wisdom, I started playing around with sparge times and found 90 minutes to be very solid advice. Based on my observations any sparge shorter than 60 minutes negatively impacts mash efficiency, and i’ve actually found very, very little difference between 60 and 90 minutes. I’ve also not experienced any increase in efficiency by going longer than 90 minutes. To back up these highly unscientific observations, when the occasional customer calls me with efficiency concerns the first question I ask now is how long did your lauter/sparge take? Inevitably, the answer is some amount of time less than 45 minutes, sometimes as low as 20. When I ask them to repeat the brew and try increasing their sparge time to over 60 minutes, I always get feedback that the longer sparge made a huge difference.

So, how do you control your lauter time? The answer is to be a lot more concerned with the wort flowing or pumping out than the water coming in. When I brew, I will to fill the boil kettle via a hose either over the top of the boil kettle or via a silicone hose attached to an inlet fitting at the top of the kettle. The reason for this is that I can pull the hose up at any time to view and measure my flow rate. This is not possible when you pump in through the bottom valve or whirlpool arm. The hose also allows me to deliver the wort under the surface of the existing liquid to avoid hot side aeration (HSA). Beyond that I do some basic math and use a small measuring bucket to determine my flow rate. For example if i’m looking for a pre-boil volume of 12 gallons, I’ll take that times 16 cups per gallon = 192 cups. Divide that by 60 minutes and you have 3.2 cups per minute. If I measure the flow over 60 seconds and adjust accordingly so that I get roughly 3 cups per minute, lautering will take a little over an hour.

Are there variables based on mash depth and mash tun configuration? Absolutely, there are tons of variables, but at the end of the day i’ve had great success with 60-90 minutes.

Cheers!