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Post by Vortex on Feb 23, 2019 6:11:44 GMT -8
Yesterday I received some samples of ceramic glass from Neoceram. They were meant to send me two different samples of different coatings but sent two the same: Neoceram-CR ceramicglass.co.uk/neoceram/neoceram-special-coatings About this coating it says: This is it after a single burn on my afterburner chamber. It's actually slightly worse than the Schott Robax was after a single use:   Looks like I'm going to have to redesign the chamber to try and get the surface of the glass farther away from the intense heat. |
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Post by drooster on Feb 23, 2019 6:51:23 GMT -8
I wonder how (and with what compounds) it polishes up to clear again?
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Post by gadget on Feb 23, 2019 12:05:50 GMT -8
Vortex,
Any thought on how much heat is lost from the glass? If you put your hand near it does it feel like a ton of heat? The viewing window is very cool. Just wondering if it take any serious amount of heat from the burn chamber. Its a very nice feature to be able to monitor plus dang I could sit there for hours watching.
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Post by DCish on Feb 23, 2019 12:18:32 GMT -8
Jeepers, that's etching? That's pretty significant!
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Post by Vortex on Feb 23, 2019 13:39:16 GMT -8
drooster I'd also like to know that, as these pieces of glass are going to be pretty useless otherwise. gadget Yeah, there's a lot of heat coming out there. Don't think it's lowering the temp much in the afterburner as all the other sides are heavily insulated and this is the exit. The stove is meant to give some instant heat and the top is 3/4" thick steel, so there's not as much instant heat coming out the top as before. I couldn't hide it now anyway, I'm mesmerized 8) @dcish Yes, I'm kind of disappointed. It looks like the coating actually suffered worse than if there was none at all, either that or Robax has better resistance to heat etching. The coating is only on one side so I will find out tomorrow, as I turned it around for today's burn, but it's still too hot to remove at the moment. How is the piece you've been using fairing, any etching showing?
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Post by DCish on Feb 23, 2019 18:05:46 GMT -8
Mine is basically fine, some minor pitting (one or two every square cm or so). But I've only been using it for periodic experimentation, and often not at the very hottest part of the burn. How hot do you think your afterburner is? In the pic above it looks like there might be some orange on the upper lip of the afterburner chamber exit. Maybe around 1700F / 900C?
- Kiln temps by color: (https://www.paragonweb.com/Kiln_Pointer.cfm?PID=464)
Lowest visible red to dark red: 885 - 1200F (473 - 648C)
Dark red to cherry red: 1200 - 1380F (648 - 748C)
Cherry red to bright cherry red: 1380 - 1500F (748 - 815C)
Bright cherry red to orange: 1500 - 1650F (815 - 898C)
Orange to yellow: 1650 - 2000F (898 - 1093C)
Yellow to light yellow: 2000 - 2400F (1093 - 1315C)
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Post by Vortex on Feb 24, 2019 3:34:23 GMT -8
The uncoated side shows a level of heat etching approx the same as the Robax after a single burn. I'm surprised yours isn't showing more degradation Brian, as it's actually closer to the hottest area. Is there much of an air gap around the edges? This video is the best I have showing the temperature colors in the afterburner: vimeo.com/315068913My IR thermometer tops out at 550C / 1022F so it's useless for this and I have no other thermometer capable of measuring above that. There's some yellows in the hottest parts. I'd estimate the glass is getting up into the 1500 - 1650F (815 - 898C) range. Neoceram's thermal shock rating is 800C / 1470F ceramicglass.co.uk/neoceram/key-thermal-and-other-properties that would explain the damage, so it's no fault of theirs. |
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Post by peterberg on Feb 24, 2019 3:57:55 GMT -8
The top window of my DSR2 development heater do consist of very old Robax. It isn't etching to date, only some very light soot that's burnt off and leaves a uniform greyish haze. This can be removed easily with a wet rag and some wood ash.
Maybe this absence of staining has something to do with the fact that the exhaust opening on top is well away from the glass, about 4". The flames aren't reaching that far although it tends to get awfully hot at the front. I'll do some temperature measurements coming week and see what the level at the inside of the glass is like. After all, I have a digital thermometer lying around and two thermocouples rated 1000 ºC.
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Post by DCish on Feb 24, 2019 12:07:19 GMT -8
Well, I've used this same piece of glass in a bunch of different positions over the past five years. At one point I was using it to look in at the spinning vortex from the side (also a very cool look, incidentally!). I think it is Neoceram, but it was an ebay purchase, and the transaction is no longer in my purchase history, so I'm not 100% sure. This latest build has only had the flame in direct contact for a burn or two, but even then, the fact that the flow of the flame front is away from the glass may be helping me. That burn had secondary air intentionally venting in along the edges of the glass, so that definitely protected it on that run. Other runs have had the slot start 2" downstream from the glass, likely providing some buffer. Your layout has the entire accumulated heat of the afterburner focused directly on the glass, seems likely to get the highest amount of heat possible focused directly on it. I don't know how different the temperature difference would be between the gasses and the glowing sidewall, but I took a look at the video you posted and compared it to this slightly more nuanced kiln firing chart, and I wouldn't be surprised if it was in the yellow-orange range, which matches temps Peter has previously reported in the 1100C (2000F) range. Peter, I'll be curious to see what your high-temp thermocouples report, that 4 inch gap might do a lot to bring temps down to a safe range for the glass. |
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Post by DCish on Feb 24, 2019 12:18:17 GMT -8
Random thought on temperature... know anyone into pottery / ceramics? A couple of kiln cones might be a relatively cheap way to get a temperature reading.
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Post by peterberg on Feb 24, 2019 13:48:47 GMT -8
There should be some mini-cones in the house, from a potter as a gift ten years ago. But for the life of me, I don't know where I left them.
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Post by Vortex on Feb 24, 2019 14:01:19 GMT -8
I've bought a thermocouple thermometer that goes up to 1300C, and some cerium oxide powder and felt polishing disks. That seems to be the industry standard for polishing scratches out of glass. Normal glass is 6 on the hardness scale, compared to Neoceram which is 7, cerium oxide is also around 7, so it might take a bit longer than regular glass.
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Post by peterberg on Feb 25, 2019 0:51:59 GMT -8
I think it is Neoceram, but it was an ebay purchase, and the transaction is no longer in my purchase history, so I'm not 100% sure. Look at the colour of the glass edge. Robax before a certain date is purple on edge, Neoceram is amber coloured. |
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Post by Vortex on Feb 25, 2019 4:57:15 GMT -8
I have a nice edge-on picture of all the different ceramic glass colors: Neoceram, Old Robax, New Robax, and old Pyroceram, but unfortunately I cant post it as I've had to change my web hosting service, so all my pictures on the forum will not work now until the migration is complete. Apologies for that.
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Post by DCish on Feb 25, 2019 5:36:09 GMT -8
Mine has a definite amber tint - thanks for the tip!
Trev, what service are you switching from / to?
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