Gushing - Calcium oxalate?

[brundage]

We are beginning to see some gushers in our canned beer. Not sure where it's coming from.

• The beer shows no microbial contaminations from in-house HLP tests (anaerobic) and White Labs tests (anaerobic, aerobic, wild).
• There are occasional calcium oxalate crystals visible at 40x.
• I'm shooting for 100 ppm calcium in my mash water using a combination of CaSO4 and CaCl additions.
• Gushing beer tastes fine

Next steps

• Verify calibration on our Zahm (we're putting together a rig to do this)
• Figure out if calcium oxalate is causing gushers
• Have a beer

Questions

• How do I figure fermenter calcium concentrations?
• What other causes should I be investigating?

Thanks

[TGTimm]

Definitely calibrate the thermometer and pressure gauges of your Zahm. If it's an older unit and has the MIG thermo, you only need to calibrate it--or rather check the calibration--once, them compensate if needed. MIG themos don't change after they're made (unless the column separates). Dial thermos need regular calibration. The Zahm pressure gauge is nice in that is easily calibrated, but problematic otherwise. Particularly, it's prone to getting beer in it and sticking. If this happens, remove the crystal (1/4 turn CCW) and rinse the dial out with lots of warm water. Carefully blow it dry, then give the innards a quick shot of a light oil. I got this procedure from Zahm. I have to do it about once a month, at which time I also check the calibration.

[brundage]

Definitely calibrate the thermometer and pressure gauges of your Zahm. If it's an older unit and has the MIG thermo, you only need to calibrate it--or rather check the calibration--once, them compensate if needed. MIG themos don't change after they're made (unless the column separates). Dial thermos need regular calibration. The Zahm pressure gauge is nice in that is easily calibrated, but problematic otherwise. Particularly, it's prone to getting beer in it and sticking. If this happens, remove the crystal (1/4 turn CCW) and rinse the dial out with lots of warm water. Carefully blow it dry, then give the innards a quick shot of a light oil. I got this procedure from Zahm. I have to do it about once a month, at which time I also check the calibration.

Good information, thanks. Our Zahm has dial gauges for both pressure & temperature. We have parts on order to rig up pressure calibration and will report back what I find.

--Dean