Applying Zircon coating to ceramic fibre blanket

[woodrascal]

Dear All

I'm having to replace my heat riser in my 5" Sidewinder batch box RMH. I'm looking to employ a '5 minute riser' using a 7 or 8" steel tube lined with ceramic fibre blanket. The existing riser is approx 850mm tall. I've read that the blanket can break down under extreme heat and give off carcinogenic particulates so I was planning to coat the ceramic blanket in the riser with a Zircon coating : see here Zircon Coating

What would be the best way to apply this coating? I was thinking of applying the Zircon to the flattened blanket BEFORE placing it in the tube and installing it in the tube when the coating was still wet - has anyone any other ideas or suggestions - what do you think?

Any help or advice gratefully received as always.

[martyn]

I dont think many people have tried what you propose, I have used up two of those Vitcas tubs, but I have not actually used it on a fibre blanket riser.
The product goes on beautifully as it is smooth and thick, I have coated ceramic fibre board in my J tube burn tunnel, it worked Ok for a 10-15 fires but then stared to peel away.
I do burn that particular stove continuously for 7-8 hours at a time.
I have also used it to coat vermiculite with similar results however I do wonder if it will last longer on actual ceramic fibre mat as it can penetrate into the material.
If I was to attempt to coat a riser, I would cut the material exactly to size and spray on a watered down coat (mix 25% water in a pump up sprayer) and them apply a thick coat with a foam roller and fit it in the tube while wet.
I dont know how your design will look or if the riser is accessible but you would need to check it and possibly replace it when necessary.
So in summery from my own limited experience, the product does not seem to adhere long term to vermiculite or ceramic board but I think it may fair better on matting.

[woodrascal]

Thanks Martyn.

I have been following your experiments with the Zircon coating with great interest and thanks for sharing them with us all.

I think the 'paint it on flat and coax it into the riser tube' is the best way to go. I'm modifying the brick 'bell' on my RMH to have a removable steel panel, so to allow me to monitor how the replacement riser performs.

It's going to be quite a major re-build (unfortunately...) so it may be some time before I get round to the job. However, I will post my experiences on the forum in due course.

Thanks again for you help and advice

[marthale]

Jun 23, 2023 7:25:06 GMT -8 woodrascal said:

Dear All

I'm having to replace my heat riser in my 5" Sidewinder batch box RMH. I'm looking to employ a '5 minute riser' using a 7 or 8" steel tube lined with ceramic fibre blanket. The existing riser is approx 850mm tall. I've read that the blanket can break down under extreme heat and give off carcinogenic particulates so I was planning to coat the ceramic blanket in the riser with a Zircon coating : see here Zircon Coating

What would be the best way to apply this coating? I was thinking of applying the Zircon to the flattened blanket BEFORE placing it in the tube and installing it in the tube when the coating was still wet - has anyone any other ideas or suggestions - what do you think?

Any help or advice gratefully received as always.

I have made ceramic risers and the coating I tried was sodium silcate.     it did stiffen it up but did not give me long term protection.

if I was to go that way again I would choose a product called "Satanite"      This product has been used in kilns, and is proven for high temps.

www.youtube.com/watch?v=Vi_OnuJKeN0


I would also not use ceramic wool, I might consider switching to Morgan superwool

2" SuperWool Plus 12x26" Ceramic Fiber Blanket ALTERNATIVE Thermal Ceramic 2192F


That would remove the dangers with ceramic fiber altogether...

[martyn]

Hi marthale, what makes you think Morgan super wool is any less dangerous that any other ceramic fibre?
All European ceramic fibre products will have been tested in their raw form but the issues start when the fibres get super heated, I am led to believe that super wool is exactly the same in that respect?
Although I know about Satanite’ i did not know it can withstand repetitive high temperatures for cycles, if that is the case then yes definatily worth looking into….

[marthale]

Jun 25, 2023 7:31:09 GMT -8 martyn said:

Hi marthale, what makes you think Morgan super wool is any less dangerous that any other ceramic fibre?
All European ceramic fibre products will have been tested in their raw form but the issues start when the fibres get super heated, I am led to believe that super wool is exactly the same in that respect?
Although I know about Satanite’ i did not know it can withstand repetitive high temperatures for cycles, if that is the case then yes definatily worth looking into….

Well,  that is how it is advertised, I am no expert on that matter, but I am offering it as an alternative.

www.morganthermalceramics.com/media/4917/superwool-boards_global_eng.pdf


Environmental & Health Safety
Superwool low biopersistent fibres manufactured by Morgan Advanced Materials are not classified as carcinogenic by
IARC or under any national regulations on a global basis. They have no requirements for warning labels under GHS
(Globally Harmonised System for the classification and labelling of chemicals).
In Europe, Superwool fibres meet the requirements specified under Note Q of European Regulation EC/1272/2008 (on
Classification, Labelling and Packaging of substances and mixtures). All Morgan Advanced Materials Superwool low
biopersistent fibre products are therefore exonerated from classification and labelling as hazardous in Europe


I have never tried it myself, but in building my next stove, i was comparing it to the other options and thought I would put it on the table to consider.

[martyn]

You can have a look here for detailed explanations donkey32.proboards.com/thread/3909/firebricks-refractories-fail-silica-flux but basically the problems start when the product gets really hot and its chemistry changes.
The fibres change into a non body soluble form than could potentially sit in you lungs for years and then come to bite you!
It seems super wool may be even more prone than other ceramic products as it has a lower temp range.
I am not an expert either, it seems that the safety standards are all based on the base product and dont account for any danger once in use?
I can tell you that ceramic fibres will produce millions of air born particles that are very visible as soon as you start handling it, these fibres may not be lethal at that stage but I dont think they are heathy and you should be wearing as mask at all times in my opinion.
I still use ceramic fibre in places where it is completely encased and have done so for many years but please treat any similar product with caution!  

[masonryrocketstove]

@moderator might want to move this thread over to the materials section? Probably fits better there.

Jun 23, 2023 7:25:06 GMT -8 woodrascal said:

What would be the best way to apply this coating? I was thinking of applying the Zircon to the flattened blanket BEFORE placing it in the tube and installing it in the tube when the coating was still wet

Vitcas’s instructions say on the website that you can thin it with water and spray it on to use it as a ceramic fiber sealer. I think they said the water:product ratio too. Vitcas is not as common to find here in the states so I haven’t tried that one. Not sure if using thinned like that works as well as rigidizing with colloidal silica first. I’d guess that you’d get better results using a rigidizer that soaks all the way in and dries to form a solid base first to paint the Zircon over. That’s how most coatings like this work best and prevent cracking.

Jun 25, 2023 5:55:48 GMT -8 marthale said:

I have made ceramic risers and the coating I tried was sodium silcate.     it did stiffen it up but did not give me long term protection.

That’s too bad, sorry to hear that. The sodium in it will actually lower the softening point and speed up the deterioration of your ceramic fiber in a wood burner. Sodium silicate dries to make the fiber good and hard at room temp.. but it also makes it melt go friable at high temps when it mixes with more ash. (There’s lots more vaporized sodium and potassium in wood ash in the riser that deposits into the surface. Those salts makes the ceramic melt, expand, and then recrystallize and shrink. Makes it fall apart a lot sooner.)

Like Martyn said, those biosoluble AES wools like Morgan Superwool are not intended to be exposed to ash on the inner liner of a solid fuel burner. AES wool is intended for oil and gas refineries and outer layer furnace insulation for industries that do heat treat with gas burners or electric resistance elements.

AES stands for Alkali Earth Silicate. The alkali in them is mostly potassium.. that’s the other main salt in wood ash. So when ppl put Morgan Superwool or other AES wool into a rocketstove riser, they’re adding more flux from the ash like that linked thread talks about. When it’s heated with all that flux, the silica changes crystal type and makes it into new chemical compounds that weren’t there when you installed it. ..AES doesn’t do that and stays biosoluble in the petroleum or heat treat industry where they don’t produce vaporized alkali salts in the ash with what they’re burning. Wood puts out a lot of ash and it goes into gas vapor phase in the really hot part of the burn ..so it soaks right into fiber real quick.

if I was to go that way again I would choose a product called "Satanite" This product has been used in kilns, and is proven for high temps.

Just curious if you’ve ever used Satanite before? It makes a very brittle coating on ceramic fiber that likes to crack when it dries and falls away if you don’t use a rigidizer before applying it. It doesn’t sink into the fiber well enough to form durable coating by itself.

A lot of knife maker guys that make little benchtop forges recommend Greenpatch 421 instead of Satanite directly on ceramic fiber because of the Satanite cracking and flaking issue. Some guys swear by Mizzou castable, but greenpatch seems to sink into the fiber a little better and create a more durable shell, at least for a knife forge. The Greanpatch 421 is meant for patching missing chunks and filling holes in refractory so it adheres a little better than a straight castable product like mizzou.

Colloidal silica is the main rigidizer you’ll find everywhere for ceramic fiber, even brand names of “specialty” CF rigidizer that don’t say it on the label. But they all use colloidal silica as the main component. Sometimes with some alumina or fireclay mixed in.

Not sure if anybody else has gone looking for ITC 100 recently but their price has tripled since last fall. Made my jaw drop when I saw the new pricing on Amazon and all the other supplier’s websites. Not just the 100 HT but all their coatings. Just isn’t worth it at that price, no matter how good it is. Looks like I might be trying the Vitcas stuff here soon, too. Or Maybe the Simond store heatgaurd stuff. Amazon reviews on that one say you definitely have to rigidize CF first before applying or it cracks away, too. ..Makes me mad because I used to like ITC. But that price gouging thing has happened a few times before and I’m not gonna buy it again when they keep doing this to their returning customers. 

[woodrascal]

Thanks to everyone for their advice and opinions on this topic - I really am grateful to you all.

[marthale]

Jun 26, 2023 19:22:55 GMT -8 masonryrocketstove said:

if I was to go that way again I would choose a product called "Satanite" This product has been used in kilns, and is proven for high temps.

Just curious if you’ve ever used Satanite before? It makes a very brittle coating on ceramic fiber that likes to crack when it dries and falls away if you don’t use a rigidizer before applying it. It doesn’t sink into the fiber well enough to form durable coating by itself.

A lot of knife maker guys that make little benchtop forges recommend Greenpatch 421 instead of Satanite directly on ceramic fiber because of the Satanite cracking and flaking issue. Some guys swear by Mizzou castable, but greenpatch seems to sink into the fiber a little better and create a more durable shell, at least for a knife forge. The Greanpatch 421 is meant for patching missing chunks and filling holes in refractory so it adheres a little better than a straight castable product like mizzou.

Colloidal silica is the main rigidizer you’ll find everywhere for ceramic fiber, even brand names of “specialty” CF rigidizer that don’t say it on the label. But they all use colloidal silica as the main component. Sometimes with some alumina or fireclay mixed in.

Not sure if anybody else has gone looking for ITC 100 recently but their price has tripled since last fall. Made my jaw drop when I saw the new pricing on Amazon and all the other supplier’s websites. Not just the 100 HT but all their coatings. Just isn’t worth it at that price, no matter how good it is. Looks like I might be trying the Vitcas stuff here soon, too. Or Maybe the Simond store heatgaurd stuff. Amazon reviews on that one say you definitely have to rigidize CF first before applying or it cracks away, too. ..Makes me mad because I used to like ITC. But that price gouging thing has happened a few times before and I’m not gonna buy it again when they keep doing this to their returning customers. 

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No, I have only watched videos on youtube watching others to get ideas of what to do for the high heat in Rocket stoves, so I turned to looking at forges...      Looking from what you have posted it appears you have lots more knowledge of hands on experience than I do,  thank you for your insights.        I sorta want to go raid NASA  which is not too far from me for some of their tiles from their space vehicles ;-) 

[martyn]

Yes I also often think about the space ship ceramic tiles and how they are made!

[masonryrocketstove]

Lol me three. Would love to get my hands on NASA ceramics. That’s the expensive stuff. I think they use a lot of exotic non-oxide ceramics like carbides, borides, and nitrides. Way over my pay grade, but I’d sure love to play with them if somebody wanted to toss them my way for free.