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Is there a way of calculating the right strike temperature?

Post #1 made 13 years ago
by Jeltz
I'm wondering if there is a formula for calculating the right strike temperature, to hit the desired mash temperature.

Imagine the school maths question: If I have 4.8kg of grain stored @ 16C and will be mashing @ 66C with 20L of water what temperature should I heat the water to 1st..... ;)

Last time I did it I went for about 72c but that gave me a mash of about 64c, ambient temperature was a little higher and there was a little less grain. Obviously if there is a way to calculate it that would be great.

As it stands I will probably aim for 76C to mash @ 66C and have a kettle boiled and a litre of iced water to tweak it.
Regards

Nic

Post #2 made 13 years ago
by Lylo
I have found that The Calculator works very well. I'm not sure why you are getting such a huge temperature drop. Generally with full volume BIAB you will only have about 2 degrees drop.
AWOL

Post #3 made 13 years ago
by Jeltz
Well that's odd, my 1st brew I went with 71 and hit 66 which is why I went 72 for the 2nd. I assumed that it was because #1 had been stored in the living room @ about 22C in late summer while #2 had been in an unheated cupboard early Autumn.

As we are now in Winter I'm assuming a greater loss.

I assume that I should be measuring the temperature of the grain bed rather than water as I have recorded a significant difference between the two.
Regards

Nic

Post #4 made 13 years ago
by BrickBrewHaus
Hey Jeltz...I've been using a formula I stole from BYO magazine a couple of years ago. It works very well for me and others that have been using it. Mashing is a fairly complex process in terms of what's going on chemically. Obviously things like grain temperature and water temperature affect things. But it turns out that mixing grain and water produces some heat of its own. This equation takes that into account very well.

StrikeTemp=(((MashTemp*((8.1489*TWN)+(0.4*GrainWeight)))-(GrainTemp*0.4*GrainWeight)-(0.5*0.0746*MashTemp*GrainWeight))/(8.1489*TWN))

A couple of very important notes about this formula:
-TWN = total water needed, i.e., volume of strike water
-All values are in pounds/gallons/degrees Fahrenheit (Sorry for the metric users, I wish I had a metric version or could convert this to metric. I don't own the issue anymore and I don't think they gave reasons for such arbitrary multipliers (8.1489).)
-This is assuming no influence from heat absorbed by the mashing vessel (e.g., a cooler mash tun that has not been pre-heated). But this works well for BIAB since the strike water is heated in the same vessel where mashing will occur.

If you search around some of my posts, you might be able to find a Calculator file I uploaded that has this equation plugged in already, it'll be a separate tab. I can't find it at the moment, but I'm pretty sure it exists.

Hope this helps.

Post #6 made 13 years ago
by Jeltz
Awesome! There is a link to a metric one amongst that thread too so I won't have to learn a new language either :D

Looks like I did something wrong with the last one or maybe the malt was colder than I thought. I'll stick the probe in the sack when I get home to see what I need to work with.
Regards

Nic

Post #8 made 13 years ago
by Jeltz
Thanks all, the mash is on.

I used the metric formula on Grain and Grape as linked on the thread that BrickBrewHaus posted.

The good thing is that it said I needed a strike temperature of nearly 70.6 to achieve a mash at 66, so I figured that something was amiss with last time.

Now, I have figured out what went wrong on #2, I need to stir the pot while its heating up as there hot and cold spots that need equalising! Obvious or what!?!

This time I hit 71 then stirred and it dropped back a few degrees, so last time when I doughed in I suspect it was really around 68 rather than 72, DOH!

Anyway I hit 71.2 and I'm mashing at 66.4 as it stands.

Thanks everyone
Regards

Nic

Post #9 made 13 years ago
by Yeasty
Thats good nic :thumbs:

One pitfall is not allowing for latent heat in your system, my pot will continue to heat the water after flame out and can give me an extra 1 - 1.5 degrees. Always give it a good stir and time to stabilise

Night night :P

Yeasty
Why is everyone talking about "Cheese"
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Post #10 made 13 years ago
by PistolPatch
Okay, had a terribly long ramble written here after beers with brewers :roll:. Let me try again with coffee :P.

Here is a spreadsheet with the strike water temp calculations that are being used in the BIABacus. From memory, the formula underneath is a metric version of the one BrickBrewHaus supplied above - good on him ;)
BIABrewer Temporary Strike Temp Calculator.xls
Important: Strike Temp Adjustment Factor

What you'll find in the attached spreadsheet is a 'Strike Water Temp Adjustment Factor'. This is important as everyone has different equipment. Heavy equipment retains heat much better than light equipment.

What Strike Water Temp Adjustment Factor Should I Use?

a) If you have a kettle that is thin-walled or an urn, you will need to strike higher. Try a factor of 0.4.

b) If you have a thick-walled kettle powered by gas on a heavy stand, you will have to strike lower. Try a factor of 0.2.

You are better to strike lower than higher with BIAB as it is easy to add temperature quickly. Reducing temperature quickly is not an option with full-volume brewing. (The original formula works on a factor of 0.41 but the default on the BIABacus is 0.3 to avoid the chance of over-heating.)

On a full-volume brew, the 1 to 2 degres above mash temp that Lylo mentioned above is also a great place to start. (Maxi-BIABers will have to strike much higher as they are using less water.)

Hopefully the above is better than I did last night :lol:,
PP
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Last edited by PistolPatch on 01 Nov 2012, 20:53, edited 2 times in total.
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Post #13 made 13 years ago
by nik
You can cope with that by using a protective grill or something like that between the element and the bag easily.
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