What am I missing?

[Koop]

It's time to ask the experts.

A while ago I posted my woes about missing the OG on Jamil's Amber Waves recipe. I decided to make my own recipe using his as a base, so I paid for BeerTools and downloaded the ProMash demo and started playing around. Here's what I came up with:

1 lb Crystal Malt 40L
1 lb Weyermann light Munich
0.5 lb American Victory
0.5 lb Crystal Malt 120L
0.2 lb UK Chocolate
3 lbs Munton Dry Amber Extract
4 lbs Briess Light Liquid Extract

The predicted OG for a 5 gallon batch was 1.069 (BeerTools) or 1.067 (ProMash) On BeerTools I input a start of boil volume of 5.5 gallons and an ending volume of 5.0 gallons. On ProMash I input an ending volume of 5 gallons and it said I need to start with 5.88 gallons.

I brewed this today, I did a partial mash at 154f with grains in a grain bag and a round Igloo cooler. Temp dropped to 150 after 30 minutes. I started with a little over 5.5 gallons (getting too close to 6 gallons is asking for a boilover with my 7.5 gallon kettle). Everything went as planned. After I cooled the wort I transfered into the fermenter. I only had about 4.25 gallons (1 - 1 1/2 qts left with the trub in the bottom of the kettle). BTW - I hopped with pellets so not a lot of loss there.

I checked my gravity and it was 1.069 - as predicted but at the wrong volume. Topping up to reach 5 gallons will drop the gravity and upset the hop balance. Adding a 2L starter will make up some of the loss but why am I missing the OG so badly?

[Petedadink]

just by guessing, how much did you loose from the kettle? Id guess you would loose a little due to trub. depending onthe type of heat sourse and length of boil will also change your loss from evaporation.

[Surgeon General]

First off, your hop balance is already slightly off from what you had planned because you planned to boil with a certain amount of sugar in solution, but you didn't hit that amount of sugar in your wort. Your beer will be a little more bitter than you had planned because your utilization was higher than you planned, so adding a little water wouldn't be a problem there- dropping your gravity by 10 points is the problem.

If you really want to hit your numbers for this beer, I'd boil 1.25# of DME with a little under a gallon of water for 10 minutes, then add it to the wort, & you should be at your gravity & volume.

As to why this happened? Well, if you are very confident in your volume measurements, then there are a couple possible problems.

-Have you used this mashing system before? You may be getting a lower efficiency than you expected.
-Have you used these extracts before? All extract will differ a couple points one way or the other from brand to brand.

I get the feeling, however, that you might not be accurately measuring your volumes here. Just a hunch. BTW, you're boiling off about 22% in your kettle, which while not directly contributing to this problem, is probably a bit on the high side. I would suggest boiling a little less weigarosly in the future.

[Koop]

If you really want to hit your numbers for this beer, I'd boil 1.25# of DME with a little under a gallon of water for 10 minutes, then add it to the wort, & you should be at your gravity & volume.

Thanks for the suggestion. I'm on it!