D.Rotblatt

DO NOT USE "Colloidal Silica as powder for adding to Epoxies as a thickener". I tried this, but it is different then the colloidal silica used for making shell molds. It ate up the ceramic wool when heat was applied, like putting glass on the wool. Look for a local foundry that does Ceramic Shell Casting and see if they'll sell/give you a quart of the colloidal silica that they use for their slurry - it comes as a liquid. As far as I know in the USA you can only buy it in 5 gal amounts from the distributer. The Zirconpax is fine. The colloidal silica comes as a liquid, so keep adding zircopax to 3-4 oz of the colloidal silica until it just starts to thicken. Thin enough to easily paint on, thick enough so it leaves a bit of a layer. A little thinner then latex paint. Takes 2-3 tablespoons zircopax to the 3-4oz of liquid. Mix it often with the brush as you are painting it on as the zircopax settles out and cakes on the bottom. Here's Remet page on Colloidal Silica in the UK: https://www.remet.com/en/remetproduct-category/shell-room/colloidal-silica/ Yes. I'm quick drying it with a hand held 1/2" burner for a couple of minutes, then turning on the forge until red inside. Let it cool and add another layer and repeat. 3-4 layers is good. Depends on how thin/thick the mixture is. Thicker mixture for 2nd and third layers. The whole process takes about an hour.

Hey Tink! Enough zircon flour to make it a little thicker then water...kind of like thinned out latex paint. You have to keep mixing it as you use it as the zircon is really heavy and quickly collects on the bottom. You are essentially making a slurry like you would for dipping a shell mold (if you have ever done that). The colloidal silica I use is Adbond II from Remet (a company in the USA which sells shell mold making supplies), NOT FUSED SILICA IN WATER. I tried that and it ate the ceramic fiber up. I used to do shell casting in my studio, so I have a gallon or two of old colloidal silica left over. I use only a couple of ounces of liquid and a few heaping tablespoons of zircon to . You might be able to get a quart of some colloidal silica from a foundry near you - that will last you many forges. Whatever type they use to make their slurry will probably be fine. Dan

I use mizzou for ribbon burners and 1/2" layer for forge floor over an insulating brick. I have also used Greenlite-45 (a 2500F insulating cartable) for furnace bottoms. I'm using Mizzou now just because I have a couple of old bags and I'm playing with ribbon burners (See the thread on "Naturally aspirated ribbon burner photo heavy" for some pics and videos). The Mizzou is working fine for my burners, it's just a bit course for the experiments I'm doing now. It has no real insulation properties, but I use ceramic fiber for that. The Greenlite-45 has some insulating properties, but is not as strong as the Mizzou. I'm also doing something which I think is unique to what others are doing. I use a zircon eggshell coating on my ceramic fiber which both protects the fiber and acts as an infrared "reflector". Using a mix of zircon flour and colloidal silica (the type used for building up ceramic shell molds). Takes only an hour or so to build up 3 or 4 layers which is a 1/16-3/32" shell over the ceramic fiber. Heats up instantly, pretty non-reactive to flux. If it's hit hard it will break or crack, but easy to paint another coat on and it seals the crack (and I'm making mostly knives, which are easy to put in and out of the forge without hitting the sides). The information is confusing because many different products work, and different ones are the "best" for different needs, but those needs are often subtle and until you've used it you don't know which is best for you. For those making a first forge, it doesn't really matter which one they choose since it will probably be rebuilt or a new one built within a year or two anyway as you use it and get to know your specific needs, and the choices which are important to you. For example, I built my last forge and after reading these threads put a 1/4" layer of Mizzou on the inside of the ceramic fiber. I couldn't believe how long my forge was taking to heat up! I ripped it out, and replaced it with my eggshell zircon/colloidal silica mix. Now it's 5 minutes to full heat. That is important to me. To someone else, the stronger structure and retained heat of the 1/4" shell would be more important. Neither is better (well, actually my way is, but....). I have babbled, Dan

Just rigidize and put satanite on the outside edges. You can put a piece of paper or masking tape on the forge bottom and edge of the top shell so it doesn't stick. The paper/tape will just burn away leaving a perfect seal (way better then the doors on my forge).

Judy, Another option: Just cut a 1" or so wide piece of ceramic fiber and just put it between the two pieces like a gasket. Rigidize it, and then if you want to change the top for a different shape you can! That is the beauty of this type of forge. OK...not Judy, just had too.... Dan

Possibly. The inside is probably really rough. The mizzou was too course to pour between the wax sprue rods - a real pain, I had to push bits down with a knife blade. Also, I'm getting a similar sound (though much less and more intermittent) on my other burner, and that has a baffle above the outlet holes. On the forced air I have to get the right mix (neutral to slightly oxidizing) to make it sing, don't know about the NARB yet til I get home. I think your first guess was closer, a little blowback forming a resonance. JHCC - thanks for that post! What a wild invention....somehow glass tubes and explosions seem a bad combination.... MOSUL - Frosty is right on. Don't get discouraged! Let us know first what you want to do and I'm sure we can direct you. As an optical engineer, please understand this is not rocket science, building a furnace is a simple thing - don't overthink. We'd love to help, the place to start is looking at the end point - what you want to do. TINK - Thanks! It does make a beautiful sound! Loud enough for any orchestra. I like the idea adding anvil percussion! Possibly. The inside is probably really rough. The mizzou was too course to pour between the wax sprue rods - a real pain, I had to push bits down with a knife blade. Also, I'm getting a similar sound (though much less and more intermittent) on my other burner, and that has a baffle above the outlet holes. On the forced air I have to get the right mix (neutral to slightly oxidizing) to make it sing, don't know about the NARB yet til I get home. I think your first guess was closer, a little blowback forming a resonance. JHCC - thanks for that post! What a wild invention....somehow glass tubes and explosions seem a bad combination.... MOSUL - Frosty is right on. Don't get discouraged! Let us know first what you want to do and I'm sure we can direct you. As an optical engineer, please understand this is not rocket science, building a furnace is a simple thing - don't overthink. We'd love to help, the place to start is looking at the end point - what you want to do. TINK - Thanks! It does make a beautiful sound! Loud enough for any orchestra. I like the idea adding anvil percussion!

Gradient, I'm curious, why use a ribbon burner for a furnace? Generally with a furnace the burner flame is coming in at the bottom, parallel to the side of the crucible and swirls around the furnace around the crucible. I'm curious what advantage you see in using a ribbon burner? Here's a couple of examples of furnaces I built over the years. The bottom one will take a #30 crucible (90 lbs of bronze). The downside of a furnace that big, is that it uses propane so fast it freezes a single cylinder (I have to couple two together or put one in a tub of water). http://www.rotblattsculpture.com/Foundry Pages/furnaces.html The #30 furnace is basically the same construction as my smaller furnace shown in this how to article. If you want more information let me know. http://www.rotblattsculpture.com/Articles/buildingabronzec.html Dan

Thanks Frosty! Works great! Out of town tomorrow, so I won't be able to try it till next weekend. It's a very resonant sound, much like an organ. It's really loud! Could be a slight bit of burn back, but it stops when it gets hot rather then getting worse. Some sort of resonance is being set up. Odd thing is that my other burner (standard build, crayon sized holes/gun powered) also does it a bit when starting up, seems to sing at around the same pitch. It's the same sized plenum (2" x 3" tubing) but it's longer by 3". The plenum is not getting hot, that's just a bit of steam or smoke from the wax burning off and the refractory curing/drying. The plenum never got so hot I couldn't touch it. At 5lbs the forge got to about 2000F. With the Reil burner in that forge I would weld at around 15lbs. With this I think 10 lbs will do it (same burner is being used as the injector assembly). Dan

The AMAZING MUSICAL FORGE!!!! Ok, I finished and got the 1/8" hole NARB set up and installed. Here's a video, works great with a few surprises! Definitely gets to heat with a really even flame.

I’ll let the forge know you’re interested, it takes care of its own posts.

Putting so close to the rear may restrict/slow the gas or air flow. The whole point of using the tapered MIG tip is to accelerate the gas speed which, I believe, then pulls air along with it. Perhaps your larger air chamber is allowing too much air in...maybe slimmer slots and only 3 instead of 4. You could try that on your next and always make them bigger if you like to tinker. Just a thought, it's working as is, so if it ain't broken...

I've got a few Mickey burners, so I have a question about the jet placement since your burner is working so well. Looking at the 4th pic, I don't even see the jet and the choke is most of the way up. Is it all the way back aligned roughly with the rear of the air openings? I always thought the jet should be further forward, just before the front side of the air openings. So my questions is; is this a function of the small size of the burner? How does it work with the jet further forward? thanks

Head slapping only if you find it entertaining I'm really excited about giving this a try though! Unfortunately I'm heading out of town for a few days next week, so It might be a few weeks until we see how it works in a forge. Hopefully it'll be setting up while I'm away.

BTW - the flames I can see in your videos look slightly green, which is a little reducing. I like that as helps prevent forge scale.

Look for the amount of flames coming out of the forge mouth (the "Dragons breath"). From my experience; none means oxidizing, just a little is around neutral and a lot is reducing, yellow flames is very reducing. That's all assuming a clean forge with all refractory cured well. I'll try to take some pics, but it never shows on camera the way I see it in person...

That’s just wood burning, I painted it with zircon/sodium silicate to try to get it to last longer. I’ll cast one up this week so we’ll see how it works soon!

OK...here's one with 123 holes. Really nice flames, plus the holes are so close together it might work to cool the block so preventing blowback. Wont' know that til I try it. Take a look!

Thanks! That'll help. It's pretty much what I'm getting, just that they're off the burner a bit. Buzzkill suggested that it was better to have them off the burner, thus keeping the burner block a bit cooler - I know from the little experience I have in ribbon burners that once in the forge it's a whole different ball game. The Joppa burners are ceramic, and look like honeycomb - very small holes close together. I don't think that would work with Mizzou (which is what I am using), as it is too coarse. Even so, the small holes seem to work well on my test...knock on wood! Weren't we talking about that a few pages back? I believe I suggested it would be easy to make a 2 part plaster mold for the waxes. Just soak the plaster in water until no bubbles are coming out and then pour wax into the mold to make tapered forms. I used to do molds like that all the time for sculptural pieces. Still do for guards and pommels if I'm doing a re-creation. In my case, I think the smaller holes, close together will also help in cooling the burner block. I'm thinking about thinning the block itself, but I haven't figured out what to put as a form - maybe build a wax box to pour the mizzou around. The idea of tapered forms for the nozzles might be easiest. ___ One last question. The flames toward either end of the block where further from the face of the block, getting closer toward the middle. Would a baffle help that...or does it really matter either way? I do notice on my gun ribbon burner that the flames toward the ends of the block are not as hot as the center...that burner does have a baffle and is 8" long. Mine is powered by a 3/4" inducer (burner) rather than a 1/2" one. But frosty suggested more holes...I'll try it and post and we'll see!

Thanks Frosty! I was thinking about the Joppa Glassworks burners. I read about them years ago and have his book on building glass furnaces (I used to do a bit of glass blowing). I'll give more a try and see what it does. Exactly what should I be looking for in the flames? As to sprue was, it's $18 for 2 oz, and 25 or so for 8 oz. Don't know how many that is, but 8oz is plenty.

That sounds logical. I have a gun ribbon burner on my other forge (first one I made, 19 normal crayon sized holes), and it doesn't hold a flame in open air, but works like a charm in the forge - my observations are consistent with what you are saying, but I have no comparison. One thing I can say, is both numbers of holes were incredibly stable. It was a complete guess as to the number of holes and it was my first try. Using crayons to burn out is a great idea, but looking at all the commercial burners out there, it seems the holes are much smaller. BTW: I have some old sprue wax, but you can buy enough for a lot of burners at amazon - not too cheap though, around $18-25 a box. Just look up 8 gauge sprue wax.

Listen to the others, but just for comparison; my plenum never gets so hot that I can't touch it....even at welding heats in the forge. The flame should never enter the plenum (except maybe a blowback when shutting off).

Hmmmm.....well let's try a link: https://youtu.be/-Y48CsDaAVQ https://youtu.be/2ZT-Re1jjzI I also changed them to public. I was trying unlisted...cause I don't think the general public is interested in this.

Frosty - need some help here! (and serendipitously, this is an example of using wood blocks to test!) Had a few hours to play so I threw together a NA ribbon burner using a DIY hybrid style burner I had around. I thought I'd try using smaller holes since I have a lot of 1/8" sprue wax I can use and I wanted it for a small forge (I figured the flame face would be shorter). So here's 2 videos of test blocks burning; one with 36 holes (first), and one with 72 holes. Its a 1.5" wide x 5.5" long block (I'm using a 2x2 for the test). Question: how do those flames look? 72 holes are definitely more stable. Is the ox/propane mix solely from the burner, or do the number of holes effect the mix as well? Thanks in advance! BTW - I've worked a lot with molds (used to teach a mold making class). In this case Vaseline is your friend. It will prevent sticking even to wood. In addition, I found an old container of A&D diaper rash ointment (my son is 16 now), and it works great as a mold release since it is thicker than Vaseline and won't get rubbed off as easily. Probably better then Crisco...

I would imagine no more than any 2" ceramic fiber shell. It's basically the same as any ceramic fiber forge, just doesn't have a layer of sheet metal around it.

A hypothetical conclusion? I guarantee it'll either make it worse or better (or the same). The only way would be to try it (we have no way to collect data on how the heat absorbs into the block), and that means actually making the burner since we have to run it for a an hour or so before we get blow back. I just looked at Joppa Glass (JLPservicesinc reminded me of them - thanks!), they have dimensions and looks like they have about a .5-3/4" thick area where the holes are. Giberson does mention that this allows the head to stay cooler. I believe these are made of ceramic. So maybe a thinner face to the block would be the way to go! Might be worth a try! It's an interesting shape for the nozzle. Wouldn't be hard to mimic and make molds for. But from your pic I see two ways to look at it. Either 1) the large chamber is the plenum, and each hole is just a tapered nozzle, or 2) each hole has a larger tube, which constricts in the end to a small tapered nozzle. It would take some experimentation to get right.