Low OG Readings

[EastBayBrewing]

I recently added a counterflow wort chiller and March brew pump to be homebrewing setup. Since I started using those two pieces of equipment my OG's have been consistently low by about 10 points (or 0.01) in my last three batches. Before using these new pieces of equipment I would pretty consistently hit my OG with an efficiency of 75%. In my last batch I even reduced my recipe efficiency to 70% and it didn't seem to help.

I've checked hydrometer calibration and that doesn't seem to make a difference of more than a few points.

Any suggestions on what could be leading to the low OG's?

 

[RM-MN]

Do you mill your own grain? Most of the time the change in efficiency is due to a change in the quality of the milling.

 

[IslandLizard]

^ +1

A chiller and pump have no impact on your OG. Efficiency wise, you can have some wort trapped in the chilling system if you don't purge it.

It's usually first milling, and then mashing/sparging related.

 

[EastBayBrewing]

Thanks for the feedback guys. My grain is milled at my brew shop and I've been milling it the same way there for a few years at least. I wouldn't have expected the pump/counterflow to impact the efficiency.

I have been targeting lower mash temps lately for pale ales and saison styles. My mash tun is just a cooler so controlling the mash temperature isn't an exact science. Maybe I've just been a little low on mash temp resulting in less sugar being created?

Any tips for improving on mashing in a cooler?

Haven't made any changes in the sparge process.

 

[IslandLizard]

Your brew shop may have "adjusted" the mill or it has slipped. Look at the crush and you'll know. You could ask them to re-adjust it or run it through twice. Small grains like wheat and rye really need their own narrower gap setting. Adding a pound (or 2) of base malt is an easy insurance to reach your OG. Your LHBS may count on that

Milling your own is the best way to have full control. A Corona mill or a generic spin-off is fairly cheap (< $50). Or save up for a roller mill if you brew enough. I bought a Monster Mill and just love it.

Tips for mashing in cooler:

• Preheat the mash tun with your strike water 5-10' before mashing. That water needs to be hotter than your target strike temp of course, and you have to find out how much hotter depending on your system and methods. Add grains when the temp has dropped to the right point.
• Use online calculator (e.g., Brew365, BrewersFriend) to calculate temp and volume of strike water. I've found I need to start at 4 degrees higher, since that's what I lose when stirring in the grains, break up dough balls, and mix it all up. I typically use 1.25-1.33 water/grain ratio. The larger the mash volume, and higher the ratio, the better it keeps its target temp (more mass inertia). But don't go too thin.
• Cover the grain bed with aluminum foil. Stick your thermometer through the foil.
• Every time you open the cooler you lose heat, so minimize doing that as much as possible.
• Have a gallon of (near) boiling water ready to raise the mash temp if it's dropping too low. Again you stand to lose a degree or 2 when opening and stirring, so count on that or you keep chasing your own tail, so to speak.
• Some people stir at the halfway point, others let it ride.
• Stir well before lautering.

I guess you're batch sparging, which is the easiest and should give you a very decent efficiency (mine is around 80-85%). Calculate the total sparge water volume needed, and do 2 sparges of equal volume. Stir well, let rest for a minute or 2, and lauter. Repeat. I sometimes catch a bit of 3rd runnings, and steep my dark grains in that, separately, or boil it on the side.

 

[EastBayBrewing]

Thanks for the feedback here guys. Excellent, technical responses. I don't think milling the grains was my issue. I've captured my thoughts on my blog. Let me know what you think. Thanks.

http://eastbaybrewing.blogspot.com/2014/07/low-og-reading-and-evaporation-during.html