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How To Mash in a Cooler Box.

(see How To Make A Mash Tun From A Cooler Box.)

First sterilize all the equipment your going to use during your brew making, Ie Boiler, Fermenter (FV), Hop Bags, Spoons, Jugs, Cooler Box, Thermometer and Hydrometer with a sterilizer such as Young's Sterilizer:

Then fill your Boiler with the amount of water your going to need for your brew. In this case I was making Black Sheep Special Bitter. I needed 11 Ltrs to Mash with and 15 Ltrs to Sparge With. = 26 Ltrs. The boiler only takes 23 Ltrs so I filled to that using hot water from the tap (hot water as its quicker to get up to the desired 75C than using cold water) and turned the element on. At this point I always add a Campden Tablet to treat the water to remove chlorine.


Whilst this is getting up to temperature I measure out the grains im going to need, using suitable scales for measuring Grams/Kilos. I measure out into a larger container ready for putting into the Cooler Box Mash Tun. (see How To Make A Mash Tun From A Cooler Box Guide for how to make one).


Once the water reaches 75C I transfer 11 Ltrs out into the Cooler Box.

Put the lid on and leave for 5-10mins for the cooler box to warm up. Then add in your grain, stirring continuously to ensure no dry clumps within the mash.

Once all stirred in take a temp reading to ensure your about 63-66C. (if above or below adjust with hot/cold water to bring within the desired temperature) Put the lid back on. I then always wrap one of my coats around it to add extra insulation, also putting a towel underneath to insulate from the cold worktop.


Take a time reading and leave for your mash period.
For me this was a 90 minute Mash.

If this is your first time using a cooler box I suggest half way through taking another temp reading to see if your still within 63-66C. If its dropped below add some warmer water to bring back within. This cooler box only drops 1C in and hour and a half so no need for me to check anymore.

Before I reach the end of my mash period I turn the boiler back on (after topping up to 15 Ltrs) to bring the temp up to 70-75C ready for sparging.


After the 90 min's Mash is up I remove the coat and put my FV underneath the tap of the cooler box..

I've tried a few different methods of sparging, the bag in the boiler & within the mash tun.

On this occasion I tried something new which worked out quite well.

First I took a sheet of tin foil from the kitchen and laid it onto the top of the grain bed and perforated small holes/slits in places on it. (This would enable me to pour my sparge water onto the foil without disturbing the grain bed, the water would pass slowly through the small holes and keep the liquid about half an inch to an inch above the grain level.)


The next thing to do is to take a few jugs of the wort from the tap and pour back into the mash tun. The first pint or so will have some of the grist and fine particles in so doing this will help to re circulate and filter out.

After doing this you then open the tap so the water passed out the Mash Tun and into your FV at a fairly slow speed. At the same time as the wort passes into the FV I top the mash tun back up with Sparge Water keeping the level about half an inch above the grain bed.


Once all the 15 Ltrs of Sparge water has been used (you dont have to use it all if you get the amount of wort out you are expecting, ie If you have 23 Ltrs in the FV at this point id stop sparging) the water level in the mash tun will obviously drop through the grain bed and when it stops turn the Mash Tun Tap off.

Then pour your Wort from your FV into your empty boiler and turn your boiler back onto its highest setting to bring it to the boil.

Whilst your waiting for the wort to reach 100C measure out your hops that you will need and put them into a hops bag.


As soon as you reach the boiling put in your first hops. You want to be getting to a continuous rolling boil.

Take a note of your boil start time so you know when your going to finish. I was doing a 90 Min boil as well.

*If using a boiler like this one I suggest leaving the lid a 3rd off.

With the lid fully on it seems to have the tendency to boil over, and that makes one heck of a mess trust me!!*

First hops went in at the start of the boil and the next hops went in half way thru the boil period.

30 min's before the end of the boil I then add in my Wort Cooler. This sterilizes the cooler.

15 Min's before the end of the boil I then add my Aroma Hops (1 Gram per Litre) and also add in.the Protofloc. (which is better than Irish Moss)


After 15 Min's turn the boiler off. At this point you can allow some Trub settling time if wish. I find I still end up sucking the trub through to the FV anyway so I dont bother.

I now connect up the Cooler IN pipe to the tap, and the OUT pipe to the drain pipe.


Turn the water on and allow the wort to cool down to about 25C.

WARNING: If using a cooler like mine please be careful when turning the water on initially. They can spit with the first bits of water passing through, and its boiling water that will be within the pipe initially.

As the wort is cooling I now get my yeast ready. I'm using Nottingham yeast as I find this a lot better than others ive used.

Get 100ml of warm water (30C) and sprinkle on the yeast, but do not stir. Put this aside for 15 min's

Once the wort is at around 25C turn the water off and remove the cooler and hop bags. (I normally try remove the hop bags as the wort is cooling but remember they will be hot.)

Again you can leave this to settle a while for the break/trub to fall to the bottom.

Turn on your boiler tap and drain the wort into your FV. Allowing it to splash into the FV is a good idea as it aerates the wort adding oxygen back into it that the yeast will need and use.

Once the wort has been transferred I then take a Hydrometer reading, taking into account the temperature of the wort at the time to give an accurate reading. Make a note of the reading. On this occasion I was at 1052, but was also a couple of litre's short of my 23Ltr. I topped the wort back up to 23 Ltrs and got a reading then of 1050 @ 21C. (the temperature of the wort will effect the reading.)

I then added 4.5 teaspoons of Yeast Nutrients into the wort. (Dissolve the Yeast Nutrient in a little water, then add to the wort)

I then get the yeast, give it a stir and add to the wort, ensuring the temp of the yeast and the temp of the wort is the same to avoid shocking the yeast.

The brew is now complete. I then place the FV into a Black Bin Bag and put in a warm room and also wrap my coat around it again as extra insulation. (this is not necessary in warmer weather.) The Black Bin Bag serves 2 purposes.

1. It prevents light getting to the wort.
2. I've have occasions where the wort has fermented like a mad thing and had spills over the top of the FV container. What a mess!! (the garage smelt great though) So with the FV inside the bin bag the spills, if any, go no where you dont want them too.

Now wait for the wort to start fermenting and then ferment out.

My brews normally start to ferment the same day and are done within a few days (down to a reading of 1010) but I normally leave within the FV for a week to 10 days to let everything drop out and settle.

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