[Iliff Ave]

How should I approach subsequent attempts at reproducing a certain beer when it comes to different alpha acids of hops?

For example, let's say the original beer had these hop additions:
24 g Spalt (3.8% AA) FWH
14 g Spalt (3.8% AA) 20 min
~17 IBUs

The spalt hops I have now are 2.5% AA. I realize that the easiest thing to do would just be to increase the amount to match the IBUs which would take approximately 50% more hops.

In attempt to conserve these lower alpha hops I was thinking about doing this:
3 g Magnum (13% AA) FWH
24 g Spalt (2.5% AA) FWH
14 g Spalt (2.5% AA) 20 min
~17 IBUs

Would that work sufficiently well? I suppose I would be getting less IBUs from the 20 minute addition and more from the FWH which could change the hop profile?

Scenario B would be:
36 g Spalt (2.5% AA) FWH
21 g Spalt (2.5% AA) 20 min
~17 IBUs

Sorry for the lengthy description of a simple inquiry...

[HoosierBrew]

Using the 3g of Magnum to stretch out your Spalt would work just fine.

[santoch]

In my experience, the later additions tend to provide pretty much the same amount of flavor and aroma, despite the %AA differences.  As such, I leave any addition later than 20 mins at the same weight.
[edit - clarification this assumes that they are all fresh, well kept hops - not old and dried out]

I then use my software to calculate the total IBUs so far in the entire batch using the alphas of the hops on hand, and make up the differences by increasing or decreasing the bittering addition.  In some cases, that may even mean altering a 60min addition to 65 or 55 mins, allowing me to use a pleasing "round number" weight.

In your case, adding Magnum would be a different twist on this tactic but an overall excellent choice, as it is very clean and neutral in flavor, and the high alpha of Magnum means it will take less to get to the same IBU levels of the original recipe.  You have a very very low alpha bittering hop, so it would take a LOT of it to make up the IBUs, and it would add a lot of vegetal material, soaking up wort and possibly imparting grassiness.  Using the lower mass of the Magnum gets you back to the IBU target with very minimal affect on the flavor/aroma and no risk of grassiness, etc.

Hope this makes sense-

[Iliff Ave]

In my experience, the later additions tend to provide pretty much the same amount of flavor and aroma, despite the %AA differences.  As such, I leave any addition later than 20 mins at the same weight.
[edit - clarification this assumes that they are all fresh, well kept hops - not old and dried out]

I then use my software to calculate the total IBUs so far in the entire batch using the alphas of the hops on hand, and make up the differences by increasing or decreasing the bittering addition.  In some cases, that may even mean altering a 60min addition to 65 or 55 mins, allowing me to use a pleasing "round number" weight.

In your case, adding Magnum would be a different twist on this tactic but an overall excellent choice, as it is very clean and neutral in flavor, and the high alpha of Magnum means it will take less to get to the same IBU levels of the original recipe.  You have a very very low alpha bittering hop, so it would take a LOT of it to make up the IBUs, and it would add a lot of vegetal material, soaking up wort and possibly imparting grassiness.  Using the lower mass of the Magnum gets you back to the IBU target with very minimal affect on the flavor/aroma and no risk of grassiness, etc.

Hope this makes sense-

That makes perfect sense and you pretty much summed up how I was approaching it. Magnum is my go to bittering hop 90% of the time and have used it in this way before.

[jtoots]

food for thought...

i've heard the statement that there is absolutely no taste or aroma that comes out of FWH/60 minute boils, so if you buy that school of thought i'm thinking it would follow that any hop swap, keeping IBUs the same, would result in identical brews... i'm just personally not quite 100% sold on the absoluteness of this one yet.

[denny]

food for thought...

i've heard the statement that there is absolutely no taste or aroma that comes out of FWH/60 minute boils, so if you buy that school of thought i'm thinking it would follow that any hop swap, keeping IBUs the same, would result in identical brews... i'm just personally not quite 100% sold on the absoluteness of this one yet.

I would definitely disagree with that.

[dmtaylor]

Sincere apologies for the following shameless copy & paste:

There are several different formulas for calculating IBUs. A lot of people use the Rager formula. However many other people including myself prefer to use Tinseth as it is a little more accurate. Most people use brewing software like BeerSmith or StrangeBrew to run the calculations. However, if you just want to learn to do it by hand, the following is the Taylor-ized Tinseth estimation method that turns out surprisingly consistent with most homebrewing software. These rules are designed for pellet hops used in 5 gallons final boil volume, 60-minute boil, @ approximately 1.060 OG.

 3.6 * oz * AA% = IBUs (bittering with hops added @ about 60 minutes)
 1.6 * oz * AA% = IBUs (flavor @ 10-15 minutes)
 0.6 * oz * AA% = IBUs (aroma @ 5 minutes)

 Add all these together, and then add another +1.5 to the final total.

 For higher gravity worts (e.g., >1.075), the primary factors are reduced somewhat to about 3.0, 1.3, and 0.6 (the last factor stays same). For low gravity worts (e.g., <1.045), the factors are increased to around 4.0, 1.9, and 0.6 (always stays same). Dry hops or very late boil additions add almost zero IBUs and can be ignored unless using a butt-ton, then add maybe an extra 2-4 IBUs, unless you're whirlpooling warm for a long time in which case you should treat them same as flavor additions per the guidance above.

 For different batch volumes other than 5 gallons, you need to multiply the final result by 5/V.

I'd treat FWH the same as a 60-minute addition... since it's in for the same 60 minutes.  If you wanted to you could add an extra 5-10% from any FWH additions to reflect reality, but if you believe in the "smoothness" thing then you might as well not calculate IBUs at all.   

Also, as the others have mentioned, you typically would not adjust amounts of hops late in the boil as far as IBUs go, but keep those amounts the same, and instead only adjust your bittering or FWH amounts to fix the IBUs.  So, figure out the IBUs from all your late additions, then subtract from the IBU goal, and back-calculate your bittering or FWH additions to ensure the IBUs stay the same.

[denny]

Dave, do you drink your beer or just take measurements? 

[Pricelessbrewing]

I would definitely disagree with that.

I've never been able to tell the difference in side by side comparisons, so I just bitter everything with warrior/magnum/whatever high AA I have on hand.

[dmtaylor]

Dave, do you drink your beer or just take measurements? 

That, my friend, is a great question.   

[denny]

I would definitely disagree with that.

I've never been able to tell the difference in side by side comparisons, so I just bitter everything with warrior/magnum/whatever high AA I have on hand.

I can tell a distinct difference between say Magnum and Chinook.

[dmtaylor]

food for thought...

i've heard the statement that there is absolutely no taste or aroma that comes out of FWH/60 minute boils, so if you buy that school of thought i'm thinking it would follow that any hop swap, keeping IBUs the same, would result in identical brews... i'm just personally not quite 100% sold on the absoluteness of this one yet.

I would definitely disagree with that.

+2 that long-boil hop selection matters.  I find that we do get more than a little flavor from bittering additions, and as such, FWH additions as well I'm sure.  Only way to know for certain is to brew a lot with zero late hop additions, which as a malthead and NOT a hophead, I've done many many many times.  My favorite bittering hop continues to be Hallertau, because I really do think it is the best and most elegant...... and I suppose it helps that it grows in my backyard.

[santoch]

Will it be exactly the same beer?  No, not exactly.  But I think it will be darn close.

I agree with all of you guys that all bittering additions are not equal and using different bittering hops makes different flavored beer.  Chinook vs Magnum?  Absolutely.
A small amount of Magnum mixed with low alpha Spalt vs 50% more low alpha Spalt vs original amount of original alpha Spalt?   My guess is that the mix will be closer to the original Spalt result than using lots of low alpha spalt will be to the original, particularly with us talking about the 17 IBU level.

[Iliff Ave]

Ok well I got home and found more of the 3.8% AA Spalt so this time around I don't have to worry about it. I think the plan to use the magnum would have got me close enough. Getting ready to collect my first runnings so I have the hops in the bucket ready to go....

This is a kolsch inspired beer. Someone here recommended using noble hops for a FWH addition. I have brewed this beer many ways and I really like the hop character imparted by the FWH addition compared to other versions.

[martinj]

food for thought...

i've heard the statement that there is absolutely no taste or aroma that comes out of FWH/60 minute boils, so if you buy that school of thought i'm thinking it would follow that any hop swap, keeping IBUs the same, would result in identical brews... i'm just personally not quite 100% sold on the absoluteness of this one yet.

I would definitely disagree with that.

+2 that long-boil hop selection matters.  I find that we do get more than a little flavor from bittering additions, and as such, FWH additions as well I'm sure.  Only way to know for certain is to brew a lot with zero late hop additions, which as a malthead and NOT a hophead, I've done many many many times.  My favorite bittering hop continues to be Hallertau, because I really do think it is the best and most elegant...... and I suppose it helps that it grows in my backyard.

I'm definitely on board with Denny and Dave here. Try bittering a given beer to about 40-45 IBUs with any noble hop, then try, say, chinook to the same 40-45 IBUs. I absolutely guarantee the difference will be very noticeable.