Efficiency and F.G. issues

I am battling a chronic high F.G. problem. It isn't high by much, maybe 5% attenuation on average. But it is enough to irritate me. I make good starters and use O2 aeration, and the hydrometer is good.

My system efficiency into the carboy is pretty reliable at 82-85%. But most of the recipes I have been using are done at 65-75%. So I have been adjusting the base malt in Beersmith to hit the O.G. But maybe this is wrong, and I am extracting more unfermentables and this is causing a high F.G.

Should I be adjusting the specialty malts as well to correct for differences in efficiency?

Typically, the specialty malts stay the same unless you change the size of the batch, 5 to 10 gallons.

What % attenuation have you been reaching? If it is not within the range, it may be your fermentation temps. Try raising the temp a few degrees the last couple days of active fermetation before transfering to secondary to help keep the yeast from going to bed.

Scaling the specialty malts vs. only bumping up the base malt depends on where you are getting the better efficiency. If your mash is better and you are getting better conversion, then lowering the base malts only sounds like the way to go. If the improved efficiency is because of better lauter efficiency, you want to scale all the grains by the same factor. But it is difficult to determine what is the case here. I’d start with scaling all the malts the same.

Given that your attenuation ends up lower than expected I suspect that your scaling of only the base malt is the cause for that. You basically increase the percentage of unfermentables in the wort which lowers the attenuation.

Give this a read: Understanding Attenuation. And maybe try the Fast Ferment Test to determine if it’s your mash or fermentation that gives you high attenuation.

Kai

I think scaling all the malts is the way to go. What I'm going to do is side by side batches with base malt scaled and all malt scaled using US-56. That should give me some idea.

Have you looked at how you take your mash temps? You might at least rule out accurate mash temperature-taking.

I'm pretty consistent about that. I use an RTD plus a lab thermometer and stir the mash every 15 min when I take my temp.

The other possibility I have been investigating is my steam mashing. It's possible I'm locally overshooting my mash temp when hitting the MLT with steam via the manifold. Even though I stir rigorously, it is still possible I guess.