Low Pre-Boil Gravity

[yipp]

I'm new to BIAB and this is the 1st recipe I've tried. I made 2 attempts at it and not having good results.

My first attempt last weekend I mashed at 168F for an hour in error and I thought that may have messed with my pre-boil gravity.

I tried again tonight keeping a close on on temperatures. I heated 4.25gal of water to 156F, removed it from the heat and slowly added my grains making sure to avoid doughballs. With the 4.25gal of water and almost 5lbs of grain I was right near the top but didn't have any loss. When I added the grain it brought the temperature down to 154F and then I made sure to keep it around 152F for 75 mins, adding heat when needed. I stirred the grains a few times during the 75 minutes.

Both attempts I ended up with a pre-boil gravity of 1.022 when the sample was cooled to room temperature. The estimated gravity was 1.035.

I boiled it vigerosly during the ended up with 1.036 as the post boil gravity.

My grains are from my local brew shop and I ran them through the mill there twice. I weighed the grain at the store and again at home to confirm the scales were accurate. I'm using regular tap water, which is good in my area and have never had a problem with it when brewing extracts. I brew on my stove using a 5 gal SS pot 12 inches in diameter. The recipe is from BeerSmith and adjusted for my setup.

I thought I had done enough research into BIAB but can't figure out what going wrong. I'm also new to BeerSmith but have gone over the recipe step-by-step and can't see a problem there.

Does anyone have any suggestions as to why my pre-boil gravity is 13 pts below estimated?

 

[RM-MN]

It might be time for you to get a grain mill of your own. Poor efficiency is almost always from a poor crush. Doing a double crush and still not extracting any more sugars than you seem to be says that the LHBS mill is set way too wide. I'll bet that the people who use a conventional mash tun never have problems draining the tun though.


For less than $30 you can get a Corona style mill delivered to your door. Tighten the setting down as tight as you can and then check your pre-boil gravity.

 

[chrishanson]

Did you squeeze the bag after you pulled it? Odds are there was a gallon or more of high sugar wort still in the bag. If you did, it's probably the crush just like RM-MN suggests.