My Partial Mash Brewing Process

The next step in home brewing that I’m going to take is to do a partial mash. I’ve discovered a partial mash is actually quite similar to doing an extract brew with steeping grains. It just involves more grains soaked for longer time with a bit more attention to temperature and ratio of water to grain. And I don’t need any additional equipment, so really it doesn’t seem like a major step to make, but I’m writing up the process anyway in order to highlight the differences. Since it’s quite similar to extract brewing and I’m using the same equipment I’ll use my extract brewing process as a basis for this.

Day prior to brew day

  1. Make a yeast starter – 100g of DME made up to 1L, boiled and cooled. Add yeast & starter to a sanatised container, shake, cover loosely and leave to ferment.
  2. Prepare plenty of ice
  3. Print out recipe
  4. Double check all ingredients
  5. Make sure equipment has been cleaned:
    • grain bag
    • fermentor
    • fermentor lid
    • tap
    • tap washer
    • airlock
    • airlock grommet
    • strainer

Brew Day

  1. If grains are not pre-milled, they will need to be crushed.
  2. Put water for mashing grains on to heat up in brew pot. Use 3L water per kg of grains, so that’s 7.5L if mashing 2.5kg grains. (Takes about 15mins to bring water up to temp on my stove).
  3. Determine strike water temperature using this online calculator. The ideal mash temperature is 65.5C. So given 2.5kg of grain and a room temperature of 22C, the strike water temperature is 73C.
  4. Place grain bag in pot. When the water is up to temperature determined in step 3, add grains, stirring while adding. Set timer for 60 mins. Give the grains a good stir about and check the temp.
  5. Wrap some towels around mash pot to help conserve temperature. A very low heat under the pot can help keep the temperature at the target mash temperature. Give the mash a stir and check the temperature every 10-15 mins.
  6. While grain is mashing, put on another pot with 4L of water to heat up to 70C for sparging the grains.
  7. Also while the grain is mashing, measure hops out in separate quantities for each hops addition.
  8. Rehydrate Irish Moss – 1 teaspoon in a small glass of water
  9. Set out empty pot with colander for sparging.
  10. After the grain has been mashed for 60 mins, lift out the grain bag and let it drain.
  11. Place grain bag in colander over the empty pot and sparge with the 4L of 70C sparge water.
  12. If doing a first wort hops addition, now is the time to do it.
  13. Add the sparging water to the brewpot and bring it up to a boil.
  14. Take hydrometer sample, cool and measure SG. Calculate brewhouse efficiency (calculator at
  15. While water is coming up to a boil, mix in the quantity of DME or LME to be added at this stage – the approximate amount that would bring the SG to around 1.050 (if not already at or above that level from the mash wort). Stir well to make sure DME/LME is fully dissolved and make sure none sticks to bottom of brew pot.
  16. As it comes up to boil, watch for hot break, then set timer at 60 mins and add first hops addition.
  17. During next 60 mins, add the additional hops additions at the appropriate times.
  18. As soon as boil is underway, heat up some water in another pot for boiling up the remaining malt extract and fermentables. If using LME, place can/jar in hot water to soften.  Add the fermentables to the pot, bring up to boil and boil for 5-10 minutes. Then place in ice water to cool.
  19. Sanitise equipment:
    • pyrex measuring jug
    • spoon
    • thermometer
    • strainer
    • fermentor
    • fermentor lid
    • tap
    • tap washer
    • airlock
    • airlock grommet
  20. Add the rehydrated Irish moss when 15mins left on main boil.
  21. Put water and ice in sink for cooling brew pot. When the main boil is complete, place the brew pot to cool. Occasionally lift out the pot and mix the ice water around in the sink and add more ice as needed.
  22. Wort should be cooled enough within 30 mins. Check that temperature is around 30C or under. Place strainer over top of fermentor and pour in the wort. Stir well with sanitised spoon and check that temperature is down to around 20C or at least no more than 24C. If not, place fermenter in fridge and wait until it is.
  23. With the lid on and finger over airlock hole, place fermentor on lap while seated and give it a good shake to mix and aerate.
  24. Take a sample for measuring OG with clean sanitised jug. DOH – I often forget this step!!!
  25. Pitch the yeast. Tighten lid on fermentor, put some sanitising solution or alcahol in airlock and insert airlock.
  26. Place in brewing fridge and, if neeeded, cool further to fermentation temp (usually 18C) and let fermentation begin.


Target 18C +/- 2C. Monitor temperature. If temperature reaches 20C, turn on fridge for awhile to bring back to 18C.

Dealing with blowouts: The airlock hole on my fermentor lid is small diameter and probably not suitable for setting up a blow off tube. So I just let it blow through the airlock, then, after it calms down, remove, clean, sanitise and replace the airlock.

Dry hopping – after 1 week open lid and toss in dry hops in a clean and sanitised bag.

Ferment in primary for 2 weeks. Check SG on day 12, 13 and 14 to confirm fermentation is complete. I usually cold crash for 4-5 days and then bottle, but I’m beginning to wonder if it’s better to skip the cold crash and keep the temp fairly constant right through to the bottle conditioning in order to not interfere with the cleaning up job that the yeast are doing in the conditioning phase.

Bottling Day

  1. Make sure dishwasher has been run – will use dishwasher racks for draining cleaned sanitised bottles. Clean up kitchen sink counters with bleach solution.
  2. Prepare priming solution:
    • Or calculate with an online priming calculator.
      e.g. 1. American Pale Ale, 23L batch: 140g sugar
      e.g. 2. English Bitter, 23L batch: 30g sugar
    • Add sugar an boiling water to pyrex jug up to 2 cups, cover with cling film and microwave to boil and sanitise
    • Cool priming solution in ice water
  3. If harvesting yeast – boil 2L of water and put in ice water to cool
  4. Fill sink up with iodophor solution and sanitise stirring spoon
  5. Clean and sanitise fermenter tap and bottle filler
  7. Pour priming solution into fermenter while stirring gently – leave for 1/2 hour
  8. Figure out how many bottles needed and Sanitise bottles in iodophor solution
  9. Also sanitise 3L container for yeast and a funnel, if harvesting
  10. Start bottling
  11. If harvesting yeast, add the 2L of sanitised water to the fermenter to mix up the yeast, pour into the sanitised 3L container and put in fridge to settle.

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