• Welcome to National Homebrew Club Ireland. Please login or sign up.
June 19, 2021, 10:34:23 PM

News:

Want to Join up ? Simply follow the instructions here
Not a forum user? Now you can join the discussion on Discord


Specific gravity question

Started by SureLook, November 01, 2020, 12:23:23 PM

Previous topic - Next topic

SureLook

I'm on my third all grain (BIAB) brew and for the third time I've failed to hit the target OG. For the first two I thought it was the grain crush as I'd bought them pre-crushed but for the most recent one I bought a grain miller and did it by hand. Followed the recipe to a tee but still fell short. As I'm doing BIAB I'm simply steeping the grains for 90 mins and agitating 4-5 times in that period. There wasnt any doughballs I could see and it seems fairly homogeneous. The mash temp was 65 C and it seemed to keep throughout. Any thoughts on what I'm doing wrong or what I could improve on. It's becoming frustrating not getting the OG I want which overall means a lower ABV in the final brew...thanks.

nigel_c

What OG did you get and what were you expecting?
Mash ph can cause a lower efficiency if you don't get close.
Problem with BIAB is that you are using a full volume. The water to grain ratio is a lot different to a mash where you sparge. That's a lot of water with a ph of around 7. I do full volume mashes and it took me a few batches to cop that ph was way off.
I'd recommend investing in a ph mater and a bottle of phosphoric acid. It'll make a big difference.

SureLook

I ws following this recipe for a belgian ale - https://www.homebrewtalk.com/threads/delerium-tremens-clone.6963/

OG should have been 1.084-85 and mine was 1.062 (pre-boil gravity was 1.042). I checked the pH with pH paper (was pH 5). I actually didnt use the full vol for the initial mash. Total pre-boil wort was approx. 21 L which came from 12 L mash water and 15 L sparge water (approx. 6L loss). The procedure I've used throughout is mashing with a smaller vol (12 L in this case) then transferring the grain bag to lukewarm sparge water (15 L) in a separate vessel and allowing it to steep for 10-15 mins then transferring the sparge water to the brew kettle after removing the bag.

The increase in gravity after the boil came from the addition of approx. 800 g of sugar as per the recipe. What sort of pH range should I be looking for in general during the mash or does it very per grain type and mash schedule?

Pheeel

Issues with your membership? PM me!


DEMPSEY

If its not your PH then it just may be you are leaving too much sugars in the mash. If you do the same process again then wait 15 minutes and sparge the spent grain with a controlled amount of water and see what more you draw off. In homebrew its good to get a decent extraction but not a panic like a commercial brewer would panic.
Dei miscendarum discipulus
Forgive us our Hangovers as we forgive those who hangover against us

nigel_c

If that's the efficiency you got the last 3 brews then that's your efficiency. A high efficiency isn't everything. If you know you are going to get 60% then work your recipe around that.

TheSumOfAllBeers

Quote from: SureLook on November 01, 2020, 12:23:23 PMI'm on my third all grain (BIAB) brew and for the third time I've failed to hit the target OG. For the first two I thought it was the grain crush as I'd bought them pre-crushed but for the most recent one I bought a grain miller and did it by hand. Followed the recipe to a tee but still fell short. As I'm doing BIAB I'm simply steeping the grains for 90 mins and agitating 4-5 times in that period. There wasnt any doughballs I could see and it seems fairly homogeneous. The mash temp was 65 C and it seemed to keep throughout. Any thoughts on what I'm doing wrong or what I could improve on. It's becoming frustrating not getting the OG I want which overall means a lower ABV in the final brew...thanks.

You need to calculate your efficiencies: your mash efficiency (post mash) and your brew house efficiency (how much 'gravity points' ended up in your fermenter.

You have several major issues here, and grain crush is not one of them:
- you dont know what your actual efficiency is, so you are probably following a recipe where it assumes e.g. 75% (or even higher efficiency), and your setup is a lot lower. BIAB is quite forgiving, and for a wide range of gravities, you should be able to hit 65-70% mash efficiency.
- you are doing something very weird with your sparge setup. When I did a dunk sparge for BIAB, I would be reserving maybe <15% of liquor for the sparge. You have maybe 60%+ of your liquor in the sparge, which means your pre sparge mash is very dense, and less efficient. You are hoping to recover the sugars with that big sparge, and its probably having the reverse effect.
- sparging serves multiple purposes. Its essential with a conventional mash tun to get any kind of decent extraction rate, and done properly it will result in the highest mash efficiencies. With BIAB its optional, but actually quite clumsy, and it is often used to work around vessel size limitations to get more volume of wort more so than address efficiency concerns.
- the big sugar addition is going to complicate your calculations of course

Summary:
- work out your actual mash efficiency and brew house efficiency
- compare it with the stated efficiency in the recipe you are following
- if your actual mash efficiency is very low (< 55%) then look into efficiency boosting techniques (double mill your grain or buy precrushed, drop the sparge entirely, or do a smaller sparge ~20% liquor),
- when rebrewing, adjust your grain bill to work with your actual efficiency
- if you are continuing to sparge, take gravity readings of your first runnings and and your sparge runnings seperately

TheSumOfAllBeers

Quote from: SureLook on November 01, 2020, 05:08:42 PMI ws following this recipe for a belgian ale - https://www.homebrewtalk.com/threads/delerium-tremens-clone.6963/

This isn't a great recipe thread. the author doesnt state his personal efficiency. so if he is getting 90% mash efficiency and you are getting 60%, then you need to use 50% more grains.

SureLook

Quote from: TheSumOfAllBeers on November 02, 2020, 11:43:59 AM
Quote from: SureLook on November 01, 2020, 12:23:23 PMI'm on my third all grain (BIAB) brew and for the third time I've failed to hit the target OG. For the first two I thought it was the grain crush as I'd bought them pre-crushed but for the most recent one I bought a grain miller and did it by hand. Followed the recipe to a tee but still fell short. As I'm doing BIAB I'm simply steeping the grains for 90 mins and agitating 4-5 times in that period. There wasnt any doughballs I could see and it seems fairly homogeneous. The mash temp was 65 C and it seemed to keep throughout. Any thoughts on what I'm doing wrong or what I could improve on. It's becoming frustrating not getting the OG I want which overall means a lower ABV in the final brew...thanks.

You need to calculate your efficiencies: your mash efficiency (post mash) and your brew house efficiency (how much 'gravity points' ended up in your fermenter.

You have several major issues here, and grain crush is not one of them:
- you dont know what your actual efficiency is, so you are probably following a recipe where it assumes e.g. 75% (or even higher efficiency), and your setup is a lot lower. BIAB is quite forgiving, and for a wide range of gravities, you should be able to hit 65-70% mash efficiency.
- you are doing something very weird with your sparge setup. When I did a dunk sparge for BIAB, I would be reserving maybe <15% of liquor for the sparge. You have maybe 60%+ of your liquor in the sparge, which means your pre sparge mash is very dense, and less efficient. You are hoping to recover the sugars with that big sparge, and its probably having the reverse effect.
- sparging serves multiple purposes. Its essential with a conventional mash tun to get any kind of decent extraction rate, and done properly it will result in the highest mash efficiencies. With BIAB its optional, but actually quite clumsy, and it is often used to work around vessel size limitations to get more volume of wort more so than address efficiency concerns.
- the big sugar addition is going to complicate your calculations of course

Summary:
- work out your actual mash efficiency and brew house efficiency
- compare it with the stated efficiency in the recipe you are following
- if your actual mash efficiency is very low (< 55%) then look into efficiency boosting techniques (double mill your grain or buy precrushed, drop the sparge entirely, or do a smaller sparge ~20% liquor),
- when rebrewing, adjust your grain bill to work with your actual efficiency
- if you are continuing to sparge, take gravity readings of your first runnings and and your sparge runnings seperately

Thanks for the insight, I'd no idea I was doing such a concentrated mash, explains the lack of efficiency. According to online calculators for the grain bill I was using I achieved approx. 75% mash efficiency and if you assume that I should have got a FG of 1.085 then my brewhouse efficiency was around 73%.

I took the sparge setup from some homebrew tutorials I saw online but thinking about it further it does seem a lot of sparge water for this BIAB set up. I'll try again and either remove the sparge completely or do as you suggest and try with 15 ish percent sparge.

nigel_c

If you use a calculator like BeerSmith it will give you all the volumes you will need.
Strike , sparge and temperatures needed.

TheSumOfAllBeers

Quote from: SureLook on November 03, 2020, 08:11:35 PMAccording to online calculators for the grain bill I was using I achieved approx. 75% mash efficiency and if you assume that I should have got a FG of 1.085 then my brewhouse efficiency was around 73%.

There is no way you go from 75% mash efficiency to 73% brewhouse unless you dump in the majority of your kettle trub in, or compress it in something like a cider press. And an online calculator cant tell you what your mash efficiency is if you are making mistakes calculating your volume (temperature corrected) and gravity (temperature corrected). You also have to watch out when inputting your malt, the non-paid for calculators can get the PPG (sugar content at 100% extraction rate) wrong.

Measuring the brew house efficiency is actually quite straightforward, if you know the malt specs of your ingredients and how much wort you collected and at what gravity. The sugar addition screws with the calculation, but not unworkably so, and you can then get the mash efficiency by working out how much liquid you left behind in the kettle.