D.Rotblatt

Thank you Frosty! I've been using Reil burners for decades, and never had them backfire when shutting off. Nor do my Mikey burners. I too have some burnout kilns where the outside shell is just 1/4" hardware cloth with 1" of kaowool. Used them for burning out ceramic shells, and have repurposed them as upright heat treat forges for hardening swords. The Zircon/Colloidal silica binder shell is fine for being just bumped. Even if it does crack or is punctured, it's easy to paint a patch on...only a few minutes, no drying time, but paint it on cool and fire the puppy up! ****I've moved the conversation to the Forges 101. Glen just told me to cut and paste it. We can move all this over there.

Mikey - I have no dog in this race! I just want to find out what works, and what works for our situation - so I hope my questions/statement didn't come off combative. Just curious and hoping to rectify a lack of knowledge. BTW: My 3000+ degree numbers are just a best guess based on melting points of the ingredients online - not any real world testing. Speaking of real world testing. Since I was putting the face on my forge today so I thought I'd try some mixes of Fused Silica against Colloidal Silica binder on some scrap pieces of ceramic fiber. RIGIDIZING The Fused Silica solution (FS) didn't soak into the fiber deeply, it stayed on the top unless the fiber was wet first. Even then it tended to stay on the surface. The Adbond II quickly soaked into the fiber quicker than water. Unfortunately when heated to red heat the Adbond II soaked fiber shrunk, the surface where it got hot turned into a solid mass. The FS formed the expected hardened layer on the surface. Another piece of fiber with only the surface 1/8" wetted with the Adbond II did rigidize fairly well. In summation, the FS solution works much better as a rigidizer, Adbond II can work if applied carefully, but if you use too much it will destroy your ceramic fiber. Adbond II is not recommended. ZIRCON/FUSED SILICA VS ZIRCON/ADBOND II A slurry of Zircon and Fused Silica was applied to a scrap of rigidized dampened ceramic fiber quickly dried in the dragons breath of the forge then put inside and brought up to red heat. It seemed to for a nice layer bonded to the surface of the fiber. I then added more Zircon to the slurry until it was the thickness of latex paint. A thick coat was applied to the surface of the fiber to make a thick second coat. This was dried the same and heated to red heat. The surface cracked (like mud) and flaked off when scraped gently. The same treatment was used for the Zircon/Adbond II mix. The second coat did not crack or come off. This was expected, since that is exactly what it is designed for when making shell molds. I even added a third coat ending up with maybe .030 or .040 thickness - like a thick egg shell. It was surprisingly strong, but a good tap with an 1/8" rod broke it. I have tested it in the past vs. flux and it is inert to flux...unless there is a crack. I went ahead and finished my forge with the FS for rigidizing, and the Zircon/Adbond II for the hardshell/emittive layer. Working on rigidized ceramic fiber made it really easy to apply the Zircon solution. I just painted it on. Fired the forge for a few seconds at a time until dry, then brought up to red heat. Let it cool (about 2-3 minutes), then applied another coat. Took me about 1 hour to face the lining. This is a really fine hard shell for surfacing the ceramic fiber, but Adbond II or any ceramic shell binder is really sold only to industry - meaning the smallest amount I've seen is 5 gal. I think I used a no more then a cup of Adbond II to do my forge (7.5" ID x 13" deep). Remet has a division for artists, so someone who is interested may want to call and talk to them and see if they will sell small amounts.

Mikey. You mentioned that the Zircon/Colloidal silica mix would not be as good at high temp as the Zircon/bentonite mix. This made me curious, so I researched it a bit. From what I can find, the colloidal silica binder is Silica Dioxide in suspension with other stuff. Silica Dioxide has a melting point upwards of 3100 degrees F. Bentonite melts at around 2200 degrees F. Seems to me that the colloidal silica binder would hold up better at high temps. It's made to bind a ceramic shell for casting steel and high temp alloys. A thought: Fumed silica is also Silica Dioxide. Since Colloidal Silica binder is expensive and only sold in 5 Gal minimum, I'll try using some fused silica and water as the binder for Zircon and see how that compares to the binder I have. -Dan

Posted this on a different thread, and Mikey suggested that I transfer the information to this thread. In a nutshell we discuss a different coating for ceramic fiber liner using Zircon and a Colloidal silica thats used in making shell molds (the brand I happen to have is Adbond II from Remet). The result is a reflective (or emissive) eggshell thick Zircon layer bonded to the ceramic fiber. ---------- I've been building forges and furnaces since the 1980's. Here's one I designed and posted several decades ago: http://www.rotblattsculpture.com/Articles/buildingabronzec.html. I've been using Reil burners and built Mikey burners as well. Now I thought I'd build a ribbon burner (or multi burner?) with a gun type delivery. I'll post some pics later. Anywho....I've been reading on how you line forges. I've done mine different. In the old days, I just used ceramic wool. When the dangers of the fibers and the wonders of the ITC stuff got publicized, I started to coat the fiber with a straight Zircon and Colloidal silica for shell casting. This was back around 10 years ago and I was teaching Art Foundry Casting at Cal State University Long Beach and got a sample of Zircon from Remet (a foundry supplier). It formed a good paper thin coating on the ceramic fiber. Heated up instantly, and stabilized the wool. I used to do a lot of shell mold casting. The colloidal silica is the binder that is used for building the layers. In shell casting, silica flour is mixed with the colloidal silica. The mold is dipped in the slurry then sprinkled with crushed silica - first layers with fine, then medium, then course. If you are casting iron, steel or a higher temperature material then bronze (I did bronze), then you use zircon flour instead of silica flour so it will take the heat. The colloidal silica is a premix that comes in 5 gallon containers. It looks like a milky water, a little thicker than water (could just be fumed silica in water, but I have no idea). The type I use is called Adbond II, and I got it from Remet. What I used to do is dab it onto wet ceramic wool with a disposable brush then just heat cure (never had the patience to just let it dry). Thickness and feel is like an eggshell (just not so smooth). One or two layers was all I use, basically to bind the outer layers so I won't be breathing in ceramic wool particles and I thought it would reflect (though now I find it's emitive...which I just found out by reading on this forum, thank you very much!). I figured since it was reflecting, a thin layer was all I needed. Seemed to work well, surface got brighter, wool was stabilized, formed a hard eggshell layer. I value a forge that heats up quick, and cools down quick. The only advantage I see of a slow cooling forge is for annealing, but if I want to do that I have an oven. A thicker heat sink liner is stronger so it holds up to more abuse, but will take a longer time to get to heat (thus use more gas). I imagine it would also act as a storage for the heat, so if a cool piece of metal is put against it it would transfer some of it's energy to the metal (but that's an argument for a denser floor rather than a dense layer of liner). The way I used to explain the advantages and disadvantages of ceramic wool vs a cast liner for furnaces is that if you are doing only one pour at a time, ceramic fiber is more efficient since it heats up quickly, but if you are doing a number of pours in a row, a cast liner is better as it holds the heat and you don't have to heat it up as much. As you say, it's really just a matter of opinion. But I think I'm starting to babble....I'll leave it at that for now. -Dan

Sure, glad to share. How? Just copy and paste? Dan

Hey Mike! Nice to virtually meet you! I used to do a lot of shell mold casting. The colloidal silica is the binder that is used for building the layers. In shell casting, silica flour is mixed with the colloidal silica. The mold is dipped in the slurry then sprinkled with crushed silica - first layers with fine, then medium, then course. If you are casting iron, steel or a higher temperature material then bronze (I did bronze), then you use zircon flour instead of silica flour so it will take the heat. The colloidal silica is a premix that comes in 5 gallon containers. It looks like a milky water, a little thicker than water (could just be fumed silica in water, but I have no idea). The type I use is called Adbond II, and I got it from Remet. What I used to do is dab it onto wet ceramic wool with a disposable brush then just heat cure (never had the patience to just let it dry). Thickness and feel is like an eggshell (just not so smooth). One or two layers was all I use, basically to bind the outer layers so I won't be breathing in ceramic wool particles and I thought it would reflect (though now I find it's emitive...which I just found out by reading on this forum, thank you very much!). I figured since it was reflecting, a thin layer was all I needed. Seemed to work well, surface got brighter, wool was stabilized, formed a hard eggshell layer. I value a forge that heats up quick, and cools down quick. The only advantage I see of a slow cooling forge is for annealing, but if I want to do that I have an oven. A thicker heat sink liner is stronger so it holds up to more abuse, but will take a longer time to get to heat (thus use more gas). I imagine it would also act as a storage for the heat, so if a cool piece of metal is put against it it would transfer some of it's energy to the metal (but that's an argument for a denser floor rather than a dense layer of liner). The way I used to explain the advantages and disadvantages of ceramic wool vs a cast liner for furnaces is that if you are doing only one pour at a time, ceramic fiber is more efficient since it heats up quickly, but if you are doing a number of pours in a row, a cast liner is better as it holds the heat and you don't have to heat it up as much. As you say, it's really just a matter of opinion. But I think I'm starting to babble....I'll leave it at that for now. BTW: First name is Dan, my son is Dave - right on both counts! Dan

Thanks Irondragon. I did peruse the "Read This First." Thanks. Partly I wanted peoples thinking on why they do a thick lining and if there are other alternatives. Here's some pics of the forge. The liner is rigidized, but not coated. I will put a bottom of some sort on it. Maybe a half brick or some refractory like Mizzou or Greenlite coated with zircon. Haven't decided yet. That's the first burn of the ribbon burner....puts out some heat! The damper is open 1/4 and I'm running at 2.5psi with three .052 holes venting into the pipe and the needle valve not open all the way. Cranked it up all the way for a moment and it will forge weld....

Never posted before, but been reading. I've been building forges and furnaces since the 1980's. Here's one I designed and posted several decades ago: http://www.rotblattsculpture.com/Articles/buildingabronzec.html. I've been using Reil burners and built Mikey burners as well. Now I thought I'd build a ribbon burner (or multi burner?) with a gun type delivery. I'll post some pics later. Anywho....I've been reading on how you line forges. I've done mine different. In the old days, I just used ceramic wool. When the dangers of the fibers and the wonders of the ITC stuff got publicized, I started to coat the fiber with a straight Zircon and Colloidal silica for shell casting. This was back around 10 years ago and I was teaching Art Foundry Casting at Cal State University Long Beach and got a sample of Zircon from Remet (a foundry supplier). It formed a good paper thin coating on the ceramic fiber. Heated up instantly, and stabilized the wool. Specs on my new forge=> Size: 9-1/2" diameter party helium tank elongated to 13" inside length. 1" inswool with flat bottom. That makes a 7-1/2" ID minus a little from the bottom. Question #1: Now what I see recommended is to first rigidize, then put on a 1/4-1/2" coat of refractory (like mizzou), then a coat of Zircon based wash. That's a massive heat sink - and really heavy. I've done fine with the paper thin coat. It lasts a long time, and if I need to I can just touch it up if it gets damaged. My forge linings last quite awhile. Question #2: Everybody is talking 2" of ceramic wool lining and seem to think that it's necessary for a welding heat. I only use one inch. The skin of the forge gets hot but I weld all the time. I did some calculations, and if the skin of the forge gets up to 300 degrees over ambient temperature, that's still only a few hundred BTU's. Even a Reil Burner puts out well over 100,000 BTU's, so the few hundred lost to the skin is minimal. The only downside is the skin gets hot. Question #3: this is for Frosty if he is around. First, thank you for all your work over the years with burners and sharing so generously! The ribbon burner I just made has 18 holes, so for kicks and giggles, I duct taped a 3/4" Mikey burner to the ribbon burner intake. It burned great! So I duct taped a 1" Mikey burner and it burned great as well. But each time I shut them down I got a huge backfire pop. My theory is that since I attached the burner to a 2-1/2" intake pipe there was large volume of unburnt gas in the plenum chamber and intake pipe that burnt when the pressure dropped. Do NA ribbon burners always do that? With a gun burner the gas is shut off with the air still pushing thus the gas will just go lean and die. With NA, the gas and pressure drop at the same time leaving gas rich air in the burner assembly and pipe. Last: Thank you Mike for your books and your generosity as well. I think I must have purchased your book right about when it came out because I made a few of your burners and was using them while I was teaching foundry back in 2006.