I have always relied on a good Starsan dunk, followed by O2 pressure, to keep my oxygen wand's sintered stone clean/sanitized. But I had read about heating to 375F for an hour in an oven to sterilize, and since my O2 rig is many years old, why not try that for insurance? Couldn't hurt, right? Check out the brownish areas that suddenly appeared, particularly in the area near where the wand and stone would have been bonded (welded)? Somehow, the heat made this happen. Is this stainless steel "rouging?" Or something else? The stone looked pristine before baking.
Interesting. Not knowing how far the wand is inserted into the stone, first thing that came to my mind was residual wort that wasn’t pushed out by O2 pressure and then got burnt/scorched in your 375° oven. Would you consider lightly scraping to see it’s only on the surface? From ROUGING: WHAT IT IS AND HOW TO AVOID IT (https://www.enerquip.com/2017/08/18/rouging-what-it-is-and-how-to-avoid-it/) "Understand common causes of rouging Though rouging is not always predictable, there are certain conditions that are more likely to cause it than others. For example, elevated temperatures above 140 degrees Fahrenheit for long periods of time are known to cause rouging. Additionally, extreme pH levels and surface damage are all common predecessors of rouging. In many cases, high temperatures and solutions with a specific pH are necessary for the processes in a manufacturing plant. In these situations, it’s important to periodically check the equipment for beginning signs of rouging or surface damage. Rough surfaces encourage rouging more than sleek ones. Electropolishing gives stainless steel a smooth surface where rouging is less likely to occur, according to BSSA. Electropolishing also provides an ideal environment for the passive layer to form and helps it maintain stability."
Interesting theory. If wort had been absorbed by the stone in an area where O2 pressure would not push it out, I suppose it could have expanded as well as scorched when heated. Right now I have it soaking in starsan solution, and will see if that softens it up at all, in case it is biological rather than metallurgical. if it does, I'm not quite sure how to scrape it away without also pushing it down into the pores. Maybe a PBW soak, though I don't really know what that would do to the pores themselves.
Reason I asked "would you consider scraping" is because I personally would be hesitant to scrape for fear of damaging the stone. Maybe boiling in distilled water would loosen it, if it can in fact be loosened. If it does soften it up I have an idea for pushing it out. It's a longshot and I'll hold it in reserve until it's softened (better to remain quiet than to open my mouth and remove all doubt, at least this time).
The Starsan soak definitely softened it. Followed by an O2 push, it's confirmed that little if any pressure reaches that upper area.
Some of the wands press fit the stone to the wand (that's what I have) and others have a cancer warning regarding California Prop 65, which I assume may refer to an adhesive used between the stone and the wand. Are you sure that your stone is welded on?
Can you identify the tan looking stuff where the stone meets the wand? If it's not gunk bubbling up from the stone (looks too uniform to be that), I'd suspect it's some sort of epoxy.
If I was in your situation and all else failed, I'd try something like this: For this I’ll assume that the area in question is receiving little if any pressure because it’s blocked on the inside by the portion of the wand that is inside the stone. After it’s about as soft as you think it’s gonna get, work fast and put 3 – 4 wraps of saran wrap around the stone at that ‘blocked’ point. Then make several uber-tight wraps with electrical tape, trying as much as possible to block the end of the stone as well. Then see if any of the gunk will blow out with pressure. Potential inefficacy of this might be because you can’t make a good enough seal, or the gunk will re-harden as soon as it gets hit with O2, CO2 or whatever. But, if you can make a good seal, maybe dip it in warmish water while ‘purging’? The saran wrap is to protect the stone from the adhesive on the electrical tape. Another (and probably easier/better) option for closing off the portion that does have flow-through would be to find some tubing with an ID close to the OD of the stone and secure it with a worm clamp, then figure how to close off the end of the tubing (plug? pinch?). If it's hi-temp tubing the stone could be simultaneously boiled and pressurized. My how things change
I'm big on DIY . . . take pride in making repairs whenever possible. But when an old 10 dollar part that's moderately important to the process goes tits up I just buy a new one. Thanks for the tip to only boil one's stone.
The stone/wand combo was more like $50+, but I see there are similar ones that are cheaper these days.
Never understood the need for a wand. What's lacking if you just attach all with flexible tubing? Because you have fouled your stone, maybe an experiment to confirm it doesn't get any worse in boiling water? Many bacteria would be interested.
My first thought as well was that it's wort that got absorbed into the stone, and well. The oven managed to push it back out. It makes sense that the area furthest away from the end of wgat;s being pushed out would receive the least amount of pressure going out. It might also be where flowthrough happens, and stuff gets sucked in. I'm not particularly concerned about any of the science. I'm just concerned with how the flow manages to pick up residue. Where your gunk occurs on the carbstone, and how it got sweated out manages to make sense of that.
Yep. I always boil my stone, then soak in Star San before use and it looks brand new. Dry heat definitely seems like it could “cook” gunk on there and make it impossible to remove. I would definitely suggest giving that a try and see it it removes your gunk.
