View Full Version : Problems hydrating Marris Otter

08-13-2009, 05:12 PM
The brewery has just decided on a couple recipes that include Marris Otter as the base. I have brewed on this system with Warminster MO one time before (at about 30% of the grist) and noticed some clumping in the grist hydrator, but assumed it was because the malt was in pretty bad shape coming out of the sack. It looked partly milled.

Last week I tried an ESB with nearly 90% Crisp MO. It was a catastrophe. At the end of the auger, we have a verticle PVC pipe (about 4" diameter and 3ft long) where the grain drops into the grist hydrator. I normally measure the temperature of the hydrated grain on its way into the mash to hit target mash temps and have been pretty successful. The MO backed up the PVC pipe, I had to have my volunteer smack it repeatedly to get the grain to come out, and adjusting water flow was no longer based on temperature but whatever I had to do to allow the grain clumps to make it through. Dry grain was falling out in big dough balls, dust was everywhere, the auger motor shut off at one point (I think it overheated). No other grain I've used so far (pilsner, wheat, Am. 2-row, munich..) have done this.

When I took a reading, the mash temperature was over 70*C. It also took double the time to mash in (about 45 minutes). Despite adding cold water down to proper temp, the beer is badly underattenuated.

Surely I am not the only one to have this problem with Marris Otter?

08-13-2009, 09:03 PM
I've never been fortunate enough to work in a brewery that was willing to buy Maris Otter, but I definitely notice a lot of clumping at home. I'm sure other people will weigh in with better ideas, but my first attempt at fixing the problem would probably involve having the water bypass the hydrator so all of the mixing occurs in the mash vessel (even though it would be a m@#$%er to stir).

If your mash vessel can be heated, you may want to try a cold dough-in. I've heard it reduces clumping.


08-14-2009, 08:14 AM
I'm 1.5 years removed from working in a brewery now, but the last time I brewed with Marris Otter, we had the grist hydrator on as it was coming into the mashtun via the augur, and we started with a glucan prep at 40 C before doing a step mash. Also, the mash rakes were going at about 15 rpm to keep things nice and uniform.

The mash schedule was 40/64/68/75 if I remember correctly. No trouble after starting with the glucan prep rest.

08-14-2009, 08:39 AM
Hmm - we usually have beautiful mashes with MO when we use it. Sounds like you were grinding it too fine. Check your grist right after the mill, and open up the mill if you are getting too much flour.

08-14-2009, 08:53 AM
Without the mention of a mill, I'm assuming you bought pre-milled? If so, be sure to specify to your vendor that you'd like a coarser grist.

08-17-2009, 09:31 AM
Have been using Thomas Fawcett Marris Otter for about a year now. I do find it is drier than most other malts we use and is a little harder to hydrate and definitely dustier.

We do not use a grist hydrator however.



08-18-2009, 01:14 AM
I find that it is worth changing the gap on my two roller for such cases. Try and try again until you get it to flow well. It's worth the hassle. Augers add more milling to the malt as well as heat and different grains/malts/moisture levels/etc mill different.:)

08-21-2009, 06:49 AM
I brewed another beer with MO (a lower % this time, about 60) and checked the crush. It was already set at a pretty coarse crush. Most of the husks are split at the middle but otherwise in tact. There is still tons of flour compared to other malts.

The clogging at the grist hydrator wasn't as extreme and I managed to mash in at a good temp, but upwards of 60% MO is certainly a problem. I am going to increase the diameter of the drop tube and try again.

Liam, how are you mashing in if not using a hydrator?

08-21-2009, 07:43 AM
Lay foundation water in mash mixer, turn on the agitator, set temperature controller for your target, and add your grist and salts. Voila! A perfect mash every time in just 7 minutes. Sometimes needs a little help with the paddle.

Seriously though. We are fortunate to be working with a pretty nifty 10 hL Miyake showpiece. We have a three vessel brewhouse: mash mixer/brewkettle with an internal calandria and mixing paddles, stand alone lauter tun with up/down raking system and grains out plough, and a very nice convexly bottomed whirlpool.

08-21-2009, 08:12 AM

We've been brewing with Maris Otter (Crisp) for over a decade - 1-2 times per week. The beer (IPA) that we primarily use it in is 100% MO. It is friable, and does clump more than most other pale malts I've used. Over time we have mashed with a grist hydrator and not. However, we have never had the problems that you have described. Never any problems in the auger, hydrator, just a little more clumping in the tun. It just takes a little more mixing.

A few things to look at:

Mill Gap (as mentioned earlier) - I have always gapped the mill for MO at 2.2mm.

Is your drop tube vented? You can insert a Y into your PVC drop tube to allow for air flow/improved grist flow.

Be very careful about allowing steam/water vapor (from the hydrator/mash tun) to flow up the drop tube and into the auger. It will really gum stuff up, especially MO. It helps to connect your auger-drop tube-hydrator-mash tun right before starting the grist flow, not earlier.

I hope one of those helps, as MO is the STUFF. A wonderful malt to brew with!