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What is the difference between a lager and an IPA in the brewing process?

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The main difference is the yeast, Ale is brewed with a top fermenting yeast s.cerevisiae[1] whereas Lager is brewed with a bottom fermenting yeast s.pastorianus[2]. From this comes the fermentation temperature, ales are fermented at higher temperatures(14-20 C) than lager(10-12 C).

A lager you would also allow to warm towards the end of the primary fermentation for a couple of days for a Diacetyl Rest, this is not required with an Ale.

Fermentation of a lager takes longer than that of an ale due to the lower temperatures.

Lagers should according to their name then be stored for a period of time in secondary/lagering vessels. This is not always required and a drinkable lager can be produced in under 2 weeks, but I, personally, would question if it should be called a lager if it has not been stored at 0-4 deg C for a week or more.

Now to be more specific and answer your question regarding IPA vs Lager:

Lagers evolved initially in Bavaria and later in Bohemia with Pilsner, in the early 1800s. IPA evolved in London then later Burton. Both these Paler varieties of what had gone before where made possible by new indirect kilning methods allowing the production of lighter malts.

This little bit of history is important as lager is usually made with a double or triple decoction mash, where as IPA are generally made with the more British single temperature infusion mash.

There are no hard and fast rules though. You could technically make either with either method, and these days many lagers are made with single infusion and I am not aware of any IPAs made with decoction.

The amount of hop bitterness is another big differentiator IPA are often highly hopped >40 IBU, commonly >60; where as lagers are in general far more subtly hopped. (20-40 IBU)

[1] https://en.wikipedia.org/wiki/Saccharomyces_cerevisiae

[2] https://en.wikipedia.org/wiki/Saccharomyces_pastorianus

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    If the ale fermentation temp is below 68°F it's still a good idea to step temp up and do a diacetyl rest for a couple days at 68°F. Diacetyl is produced by both lager and ale yeasts. – Evil Zymurgist May 2 '17 at 13:52
  • EZ I have never done this previously I will give it a shot next time round. – Mr_road May 2 '17 at 15:49
  • I ferment pretty much every ale I make between 55-63F and have never needed a diacetyl rest. – Denny Conn May 8 '17 at 15:45
  • I have never done and never needed a diacetyl rest when making beer. I do however use a long bottle conditioning/ageing process.I find it hard to imagine that lager brewers of yesteryear had a diacetyl rest either. Maybe they rolled all the barrels out of the lagering store and then rolled them all back in after a day or so in teh sunshine - but I doubt it1 – barking.pete Aug 21 '17 at 10:14
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In addition to Mr_Roads answer.

Lager yeast is unique from ale yeast in that it can breakdown and use melibiose, which is a sugar not fermentable by ale yeasts. This is one reason lagers are generally "cleaner" in mouth feel and residual sweetness over ales with the same recipe.

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Simply put, there are two overarching umbrellas in beer... ales and lagers. An IPA is an ale. GENERALLY speaking all beers fit under one of these two umbrellas. Once under one of these umbrellas the main difference is brewing technique. Even if you use the exact same ingredients and technique between a beer with ale yeast and the other with lager yeast, one is still an ale and the other is still a lager. You would rarely use the same technique between the two but that's not the point here.

What can make this a confusing concept to learn is that lager is not only a description but can also be a verb whereas ale doesn't have this usage. An ale is just a description. To "lager" (verb) is a process of conditioning beer (AKA letting it sit) at low temps for an extended amount of time. You can lager any beer, even an ale. Furthermore, you don't necessarily have to lager (verb) a lager (descriptor). The classic example is Anchor Steam which originally was a lager (because it uses a lager yeast) brewed at higher than normal temps, though many people nowadays still apply some level of lagering.

In short, an IPA is an ale and can never be a lager. If you use the same ingredients for an IPA but use lager yeast and then lager it, it becomes an IPL.

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the ingredients are different.. and lager is fermented for a longer time at a lower temperature.

  • no, the ingredients other than yeast can be exactly the same – Denny Conn May 8 '17 at 15:45
  • well.. when i make ipa i use maris otter barley and styrian and challenger hops, us05 yeast. It takes 7 days at 18 degrees. When i make lager o use helletauer or saaz, and lager malt. Which is kilned differently. The idea with lager is to remove certain flavours that ale includes, by changing most of the process. – Richard May 8 '17 at 16:03
  • But you seem to be thinking of only one type of lager. Any ingredient that us used to make ale can be used to make lager, except the yeast. – Denny Conn May 8 '17 at 16:51
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    We seem to be talking at crfoss purposes. Of course lagering an ale doesn't make it a lager. But other than the yeast, the same ingredients can be used for each. For instance, the grist and hops for an alt (ale) can also be used to make an Octoberfest (a lager). Both are fermented cold and lagered after fermentation. The difference is the yeast. – Denny Conn May 9 '17 at 15:31
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    Richard, you're only thinking about one type of lager. What about Octoberfest? What about bock and doppelbock? Those use darker kilned malts. They are also not crisp and fizzy. They are dark and rich. I think you need to go look at beer styles (maybe at bjcp.org) and learn more about lagers. – Denny Conn May 9 '17 at 16:52

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