I had my first encounter with beer stone recently. My fermenter chiller coils have been collecting a residue that does not come off easily. Normally, to clean them, I run a Scotch brite pads along the coils with some Barkeepers. Then I rinse well and dip in a StarSan solution and let air dry. The coil looks clean while wet. Afterward it dries I notice the residue. At first I thought it may be residual StarSan that dried up but the last time I used the coil, there was a lot more residue.
This is a close up of my chiller coil I put in my fermenter to keep temps with glycol. I have seen this residue on the coil before but not near this much. The picture of the coil is after cleaning with a Scothbrite pad and Barkeepers.
Upon swirling the cup, it did not act like yeast, which would make the solution milky. It acted more like miniature grits or something and quickly settled out. So I took a sample an eyedropper and put it on a slide and checked under the microscope. The microscope picture is at 430X.
Next, I tried soaking the coil in a BarKeepers solution for two hours. That didn’t seem to help at all, so I soaked in a standard StarSan solution for 30 minutes. That seems to help a little the the residue is still stubborn.
Now the residue on the coil looks a little whiter and when rubbed with my finger would create some powder. The residue flaked off a little easier with a knife blade to get a sample for the microscope.
Here is a picture under the microscope at 430X:
After talking with some folks at my local homebrew club, we determined the residue is beer stone, or more scientifically, calcium oxalate (C2CaO4). So, I ordered some Five Star B.S. Remover and will update here with results.
Follow up: I soaked the coil in the recommended solution of BS Remover for ten minutes per directions. There was still a good bit of residue on the coil. So, I let it soak for another 3-4 hours. That did removed a lot of the beer stone, but there was still a good bit remaining. I went over the coils with a Scotchbrite pad and got almost all of it off. There is still a very little bit on the coil. I was hoping to be able to soak it and have the beer stone get eaten off, but some mild elbow grease was required.
