To work out the appropriate IBU's for an all grain beer, you can use software such as the online beer recipator program, promash or beersmith, etc etc...
The level of IBU's depends primary on the gravity of the wort during the boil, the Alpha Acid percentage rating of the hops, how long the hops are boiled for and the amount added. Glen Tinseth has a handy calculator
here... but you need to convert metric to imperial. For more info on International Bittering Units (IBU) you might want to read the relevant section in John Palmer's book on brewing -
click here for the Chapter on Hop Bittering...
For a partial, you should be doing a 60 minute boil - not unlike the allgrain brewers do.
As a very general rule - The hops added at the start of the boil will contribute to overall bittering, hops added at around the 20 to 30 minute mark will add flavour compounds and hops added in the last 5 or so minutes of the boil will contribute the aroma profile of the beer. You have Cascade hops which are excellent flavouring and aroma hops for a pale ale. I'm not all that keen on them as bittering hops but I suppose you could use them at the start of the boil if you have nothing else. I'd recommend you visit the brew shop and grab some bittering hops such as Northern Brewer / Nugget / Perle etc and use these hops to bitter at the start of the boil and then add some Cascades at the 20 minute and 2 minutes remaining mark of the boil for some flavouring and aroma additions, respectively. Without knowing your exact preboil gravity and volume, it's hard to say exactly how much hops to add, but you might want to start with the following hop bill and adjust to suit your tastes for future brews:
Start of boil - add 16g of Northern Brewer (assuming it's around 7% A/A)
20 mins to go - add 16g of Cascade, and
2 mins to go - add 12g of Cascade.
**Note - this is assuming that the boil is a concentrated boil and not an all grain boil and I haven't got access to Promash at this time, so don't flame me, I'm making a semi-educated wild assed guess!!
In the case of a partial, adding hops without prior experience can get a bit tricky, especially when you're probably doing a concentrated boil - by that, I mean that the boil gravity will be much higher than the target gravity you hope to achieve at the start of fermentation and so the isomerisation extraction efficiency of the hops will be reduced by the higher gravity of the boil. Obviously I'm assuming that after the boil and chill, you add the wort to the fermenter and then fill with fresh water to achieve the desired target gravity and/or volume.
If you use a kit, you only add it to the boil if you want to remove the flavouring and aroma properties of the kit. So, normally you'd add the kit at flameout, stir though gently and then start the chill - this way you preserve most of the flavour and aroma properties of the kit. Adding a cooled kit will also help drop the temp of the boiled wort too. One other point - adding a kit at the end of the boil will logically help hop extraction efficiency because the wort's gravity would have been much higher if you'd added the kit at the start of the boil, so it helps you get more out of your hop additions by holding back on tossing in the kit...
Also remember that you are now in the post-boil world and the wort is vulnerable to infection from now on so make sure that you don't use some filthy spoon to scrape the kit contents into the wort. Use the relatively safe stirrer you used when you boiled and stirred the wort to stop if from burning the bottom of the kettle...
BTW, if you plan on using yeast other than the generic yeast that came with the Coopers kit, then empty the sachet of Coopers kit yeast into the boil in the last 10 mins to add some cheap yeast nutrient to the wort - yes, it's killing the yeast, but the cells are a source of proteins and amino acids for the fermenting yeasts to feed off! It's a dog eat dog world in the fermenter, you know!
h34r:
Cheers,
TL
