Can You Let Mash Sit For Too Long? (Mash Length and Temp)

I love increasing efficiency and getting the very most out of my ingredients as does my homebrew buddy. We want a nice high gravity as we extract the most sugars we possibly can from the grain. So naturally I wondered if there is an upper limit to the length of time I could let mash sit.

The majority of all-grain beers sit in a mash for approximately one hour. Extending the length of time past an hour does little to extract and convert more sugars. Temperature poses a bigger issue than time, since a drop in temperature will decrease the body of the beer.

Lautering is the full description of the process to extract sugars from the grain to create wort. Mashing is the part of the process where the water sits at a specific temperature to convert the sugars.

The process can be a bit complicated and understanding at least some of the science will give you an edge in creating better beers. Read below as I explain in simple terms how to mash like a pro.

Mash Length and Its Affects on Your Beer

When brewing all grain you will need to mash. In order to do this many will either use one of two methods. Brew in a Bag or Sparge. Both of these methods require time and temperature to work properly.

You can actually mash for as long or as short as you want to, but you may not get the desired results. For example you could finish your mash in as little as 20 minutes, but you might not be pushing your ingredients to the limit. I mean you paid good money for them so you might as well take the time to extract them fully.

The recommended time that everyone suggests is one hour. This hour will give the mash enough time to fully convert all the sugars. If you wanted to go longer than this I’m sure you could get more out, but the benefit is likely not worth the added time cost.

What Happens if You Mash Longer

The longer you have your mash sitting, the more the conversions will take place, but something else will happen. You will lose heat. If this heat loss is too great any sugars that are being converted will be much thinner.

But, Since most of the conversion has already taken place you probably won’t have too much change to your beer. Here are a few things that can happen as you mash for too long.

  • Stuck mash if temperatures cool and gel the grain and sugars together.
  • Mold and fungi if allowed to sit for a very long time at cooler temperatures.
  • Longer mashes could result in thinner beer from lower temperatures.

Its often thought than longer mash times or disturbing the grain will result in tannins. The definitive answer is tannins only come from temperatures above 170F hitting the grains. It extracts those bitter flavors that are not pleasant.

Mashing Out or Filling Your Pot

Mashing out is often included in the 60 minute mash time, although you could go longer and shorter if you wish. Mash Out time Should take you 10 minutes, but there is no set time limit.

Typically when its time to mash out or begin pouring the wort into your brewing vessel, you will want to push warmer temperatures at around 170F in order to ensure your wort flows smoothly out and does not get stuck.

Since oatmeal and wheat can have a big problem with this due to no husks, rice hulls are often added in order to help filter wort through.

Photo of me doing the vorlauf.

Also when you begin to mash out you will need to make sure that you vorlauf. Its important to clear of the liquid passing into the pot so you don’t get unfermentable chunks of grain into the beer boil.

Brew in a Bag

Watch your temperature closely when you are using the brew in a bag method. This is more important than the length of time you are mashing.

When you are doing brew in a bag its as simple as just lifting the bag of grains out of the pot in order to begin the boiling process.

Its often asked if squeezing the bag is OK. Generally I would say that it is except that you will likely get unfermentable chunks of grain in your wort. But other than that you should be fine.

Why Is Sparging Necessary After Mashing?

Its actually not necessary. You could do a single mash and mash out and then be on your way. What sparging accomplishes is rinsing of your grains in order to push as many sugars out as possible.

Some brewers will call this process rinsing the grains. But it’s also interesting that some sparges happen continually throughout the mashing process. This is thought to increase the efficiency and maximize sugar conversions.

Its also sort of the same thing that we do when we do the vorlauf that I mentioned above. Although its only done at the end of the mash rather than throughout the entire mash.

The Sparge Arm

The sparge arm essentially allows your to recirculate the water by spreading it out so it doesn’t flow to quickly to the bottom without touching as much grain as it can.

So I don’t like spending a ton of money on things that don’t improve my life that much that’s why we use the patented frugal sparge arm.

It’s just a pot and spaghetti strainer if you didn’t notice. But its the cheapest way I know of. But many systems actually have them built in. But, they are expensive!

There are also a lot of DIY ones that you can find online with a quick google search.

But, if your just lazy and have cash to burn plus want to be super efficient then you can buy a fancy sparge arm. I mean, it is efficient and hands free at least.

Overnight Mash with Auto Systems

So, I know I said temperature was an issue when it came to mashing for longer times. But hey, there are auto brewing systems now so I can save time and mash overnight.

Its a valid point as you can split up the brew day. It also changes the beer a bit. But others have attempted it with success. However you want to measure it, they made beer and in the end I guess that’s what matters.

There are a lot of automatic electric brewing systems on the market that automate the mash step. Here are just a few:

Whether or not its safe is yet to be determined. I wouldn’t want it running in case there was an electrical issue. I’m sure the robo brewers also don’t want you doing that either.

Do Other Malts Need to Mash Longer?

Other malts don’t necessarily need longer mash times. We often blend a variety of malts in the mash and always mash for the same length of time.

Some might want to mash longer simply because they want to reduce the temperature and let it rest at that temperature to create different sugar chains.

Step Mash

A step mash is the process of letting the grain sit at a certain temperature for 20 minutes and then increasing the temperature for the remaining mash time.

This allows for more sugars that the yeast will eat that will add to the beer flavor at lower temperatures but could also dry out the beer if to many sugars are processes by the yeast.

At higher temperatures sugars become more difficult to ferment leaving more sugar in the beer adding body and flavor.


Hey, I'm the the creator of I have been brewing beer since 2013 and started by brewing in my parents home. I have written copy on numerous websites. Most notably Seeking Alpha, where I analyze small cap publicly traded companies. I have also written content for and

Recent Posts