Scaling a recipe for boil time

i have a pretty tasty american wheat beer that i just tapped but there are a few things i'd like to change. i'd like to lighten the color and drop the OG a bit. i moved some of the grain ratios around and decreased the total but that only got me so far with color. i usually do 90m boils, so i think that the best way to decrease color is to cut the boil down to 45m to avoid caramelization and reduce maillard reactions. my problem is i can't figure out how to adjust my grain weight / efficiency to make it all work. the only way i can cut my boil time in half and hit a specific OG at the same volume as before is to decrease my boil volume and thus my efficiency. i know what boil volume i need, but changing that and boil time doesn't do anything to efficiency or grain weight. maybe i've been tasting to long tonight, but am i missing something obvious? using beersmith.

What was your original recipe/process?

A 90 minute boil seems like a long time for a wheat. The only time I boil longer than 60 min is when I need to extract a buttload of hop bitterness for a double IPA. (Or for high grav beers when I have to sparge a bunch then boil off).

Decreasing your grain/extract bill will lighten both color and gravity. Be sure to reduce hops as well to keep everything balanced.

I agree that a 60 minute boil should be all you need for just about any beer. Without your recipe or, at least, your specs, we cannot know what you want to achieve. However, if you are trying to lower your OG, you should be able to get by just fine on a 60 minute boil.


TL

You will only make light colored beer using malt that is light to start with. Look at the SRM for each grain (grain charts on the internet). A 2 SRM is very light and so if you only used grains that were 2 SRM it would be very light in color. White Wheat can be used to lighten color. Rice can also be used (whole or flaked or rice syrup). If you boil 1 hour you will not darken the beer if you cool quickly it will maintain the color but if you just let it cool in ambient temperature it will darken (not recommended).
Obvisouly the more malted barley grain you use the darker the yellow color will be and so then other adjuncts I mentioned above can be used to substitute for the barley and make the beer lighter and lighten the yellow color if that is your intention.

The BeerSmith program can show you the color of beer that you design and I highly recommend it.