techniques for lightest possible color: reduced boiling

i'm getting started on a kolsch this afternoon and i'd like to reduce the color as much as possible. to this end i want to reduce the boil to 45 min. i need some help in figuring my efficiency to make up for less boil off. my usual numbers are as follows:

90 min boil, 8.75g in to boiler, boiled down to 6g, efficiency is consistently 80-85%. i've already figured to reduce my volume into boiler to 7.75g. can anyone help me figure a new efficiency % to make up for less volume!?

TIA!

I would not do that. A Kolsch requires Pilsner malt and pilsner malt requires atleast a 60 min boil to get rid of DMS. Im guessing you would rather have a slightly darker beer (4 srm) than one that tastes like canned corn of veggies.

If you have an immersion chiller you can get away with a 60 minute boil. Be sure to get it under 120*F quickly. Me, I'm still happy with the color even with a 90 minute boil. I'm not trying to clone Bud Light.

Get the best fruggen Eff% you can...very low mash temp for very long time..maybe add soem rice or corn to up the fermentables without color and then cut it with water to get back into the OG for the Style.

thanks for the replies. Rev- as soon as i posted i realized exactly what you said! i've decided to return to the 90 min boil. getting it done today is more important than droping a few tenths SRM. in the future i'll play around with the corn idea. thanks!

Check out Designing Great Beers by Ray Daniels as well. There is a whole chapter about the myriad of items that affect beer color.