Ever since I added a sight glass to my spike conical I believe I’m tasting some oxidation in my beer if it sits in the conical for more than a couple weeks. There is no direct Sun on the sightglass but it would get some diffused through a window and blinds. Has anyone else had this issue? It could obviously be something else in my process so before I start wrapping it in tinfoil or something I wanted to ask the question. Seems like there are enough sight glasses out there that others would have similar issues if it was really a thing. Theoretically it’s possible, but does it happen in practice?
Oxidation from sight glass
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Mix of silicon and PTFE for the tri-clover gaskets. Not sure what the o-rings in the spike sampling valve and sight glass are. Why, is there a know oxygen permeability with one of these?
One can drive a truck between "oxidized" and "skunked", as their characters and causes are completely different from each other.
Wrt "skunked", that's light-struck hop compounds. If you're recirculating hopped wort through your sight glass I suppose there's a risk of "skunked" but I have to say unless you're brewing under blue<->UV light or outdoors in bright sun I doubt that's in play.
Wrt "oxidized", well, there is some attenuation of desirable character induced during the brew if one doesn't adhere to low oxygen brewing, but most folks would be unlikely to notice. The worst of "oxidized" is usually a post-fermentation oxygen exposure problem. I would look there for that...
Cheers!
Wrt "skunked", that's light-struck hop compounds. If you're recirculating hopped wort through your sight glass I suppose there's a risk of "skunked" but I have to say unless you're brewing under blue<->UV light or outdoors in bright sun I doubt that's in play.
Wrt "oxidized", well, there is some attenuation of desirable character induced during the brew if one doesn't adhere to low oxygen brewing, but most folks would be unlikely to notice. The worst of "oxidized" is usually a post-fermentation oxygen exposure problem. I would look there for that...
Cheers!
This is during fermentation in a pressurized conical not during brewing. At 5-7 PSI I really doubt I'm getting any significant oxygen ingress. After fermentation I tend to pull off one keg from the conical (closed system co2 transfer), a week or two later I'll pull off another keg and it'll taste a bit off but not so much that I can tell what side of that "truck" I'm on. The beer is kept cold in the conical during this time. The only variable that changed in my last few batches where I've noticed this is the addition of the sight glass so that I can see the yeast/trub that has accumulated at the dump valve.
What kind of tubing is the sightglass made of?
Glass and stainless
You can get TC gaskets made of different materials, each with their own advantages/disadvantages. Silicone is good for its high temperature range, so it makes sense on a kettle. But it is not as good at keeping oxygen out. So longer term seals like fermentors and kegs should look to use alternatives like EPDM.
I did some research/investigation on this for a review I was doing a few months back and it's hard to find good comparison data out there. I was able to find one research paper that was from the commercial brewing world and they measure oxygen uptake of the beer when they used Silicone vs. EPDM gaskets on their large (5"?) TC fittings. They found Silicone allowed in 25x as much oxygen as EPDM. Silicone tubing in fact is used in some medical applications specifically because of its ability to pass oxygen through it.
Now all of this being said, you'll probably say that you always had the TC fitting on your fermentor and you didn't change your gasket when you added the sight glass, so is any of this really relevant? Maybe not directly, but if you are looking at ways oxygen can get into your beer while sitting in your fermentor, you should seek out TC gaskets from a material other than Silicone.
Your sight glass will have some kind of caulk/sealant between the glass and stainless parts. Both glass and stainless themselves are great oxygen barriers, but maybe the sealant they used between these parts is the weak spot for oxygen ingress (a lot of caulks are silicone).
To get around this, you could look for a TC end cap made 100% out of some clear material like acrylic or glass (but I have no idea on the oxygen transmissibility of acrylic, so that's definitely worth some research). I didn't find much of these on the web, but did find this: Tri-Clamp Sight Glass End Cap | Sanitary Fittings [Buy Online]
Stout tanks and kettles sells them too: Buy End Cap Sight Glasses | Stainless Steel Parts & Accessories Store
I did some research/investigation on this for a review I was doing a few months back and it's hard to find good comparison data out there. I was able to find one research paper that was from the commercial brewing world and they measure oxygen uptake of the beer when they used Silicone vs. EPDM gaskets on their large (5"?) TC fittings. They found Silicone allowed in 25x as much oxygen as EPDM. Silicone tubing in fact is used in some medical applications specifically because of its ability to pass oxygen through it.
Now all of this being said, you'll probably say that you always had the TC fitting on your fermentor and you didn't change your gasket when you added the sight glass, so is any of this really relevant? Maybe not directly, but if you are looking at ways oxygen can get into your beer while sitting in your fermentor, you should seek out TC gaskets from a material other than Silicone.
Your sight glass will have some kind of caulk/sealant between the glass and stainless parts. Both glass and stainless themselves are great oxygen barriers, but maybe the sealant they used between these parts is the weak spot for oxygen ingress (a lot of caulks are silicone).
To get around this, you could look for a TC end cap made 100% out of some clear material like acrylic or glass (but I have no idea on the oxygen transmissibility of acrylic, so that's definitely worth some research). I didn't find much of these on the web, but did find this: Tri-Clamp Sight Glass End Cap | Sanitary Fittings [Buy Online]
Stout tanks and kettles sells them too: Buy End Cap Sight Glasses | Stainless Steel Parts & Accessories Store
I’m skeptical, but I do find this interesting and some of my seals are probably due for replacement anyway. Thanks for the info.
Just to debunk the myth, pressure is not the key factor, but partial pressure, which considers also the gradient of the particular gas component.
While you have 5-7 psi of CO2 above atmosphere, you have -3psi of O2 inside your conical (-14.7psi x 21% O2 concentration). If you have O2 permeable materials, the O2 gradient will push through them into fermenter, but only at the rate of permeability and the exposed surface into head space / liquid.
But since you clarified it is skunked and not oxidized, then UV is your primary vector - why not just break out the tinfoil (hat) to test it?
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