Paraphrased from Brewing Classic Styles (Palmer,Zainasheff 2007)
There are 3 IPA's. In increasing hoppiness: English, American, and Imperial.
The English IPA uses English grains, Pale Ale Malt and as opposed to other English beers the late hop character is more pronounced. English needs a dry finish so pick an attenuative yeast. Lower mash temps are recommended to help achieve the lower FG.
OG: 1.062
FG: 1.015
IBU: 50
SRM: 11
60 min boil, preboil volume 7G, preboil gravity 1.053
5.5 Gal
12.25# Brit. Pale ale malt
.5# Wheat malt
.5# Biscuit
.5# Crystal 40L
6 oz Crystal 120
1.4 oz Challenger 8% 60 min. 44.3 IBU
1.5 oz. Fuggles 5% 10 min. 5.8 IBU
1.5 oz Kent Goldings 5% 0 min.
Mash at 152 for 70 min
Notty yeast or Wyeast 1028
American IPA uses American base grain, 2 row - should have a high hop bitterness and use American hops - more citrusy, piney, fruity, and resiny. Malt flavors and aromas should be less than English IPA's. Wyeast 1056 or Safale US-05 and Mash at 149 for 90 min.
OG: 1.065
FG: 1.012
IBU: 64
Color: 7 SRM
60 min boil, preboil volume 7 gallons, preboil gravity: 1.055
12.75# American 2-row
.75# Munich Malt
1# Crystal 15L
.25# Crystal 40L
Horizon 13% 60 min 49.7 IBU
Centennial 9% 10 min 6.9 IBU
Simcoe 12% 5 min 7.6 IBU
Amarillo 9% 0 min
Mash 149 for 90 min
Then there are Imperial IPAs with insane amounts of hops (well
) they have less crystal character than the American and English IPA's and they need to finish at a gravity between 1.012 - 1.015 ... Imperials have sugar added to them in order to get the gravity up... not only do they use a lot of hops but it is important to use the correct kinds/combinations of hops.
OG: 1.080
FG: 1.013
IBU: 100+
Color: 6 SRM
Boil 90 min, preboil gravity 7.74 gal. preboil gravity 1.062
15.25# American 2-row
.5# Wheat malt
1.5# Corn Sugar
.5# Crystal 40L
2oz Warrior 15% 90 min
2 oz Chinook 13% 90 min
1 oz Simcoe 12% 45 min
1 oz Columbus 14% 30 min
2.25oz Centennial 9% 0 min
1 oz Simcoe 12% 0 min
Use Wyeast 1056 or Safale US-05 make a 2L starter if you use 1056
Mash @ 150 for 90 min
Hope this helps