Daguy

Preferred Refractories for Chamber vs Ribbon Burner

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So, just to bring a question to the beginning of a thread that I've had to dig deep into several threads to find any info on (and I'm still not satisfied I've gotten all the info I need for my build), let me ask a question or two.  Which castable refractory would our senior members recommend for the ribbon burner, the forge body, and the forge floor, if one decides to cast it rather than brick or kiln shelf it. And why?  If a particular brand is not recommended, what properties should one look for in the material one chooses for each of these components?

The internet has such a confusing glut of conflicting information (and even here, threads wander), I'd just like to get some opinions from experienced guys. I apologize to those who have addressed these questions before, but I think future questers (Not to mention myself, now)  will appreciate having these particular questions addressed early in a thread.

Let me also say that the reason I am asking these questions here is that, as my personal curiosity has moved into this area, Iforgeiron forums is where I have found the most down-to-earth, basic "guys who are just interested in this stuff and VERY willing to share with other guys" people.  I appreciate that. 

Your expertise and our locations do not lend themselves to an apprenticeship type learning relationship, so there is nothing we newbies can give back to the "Masters", though we would if we could.  If you would all just indulge us, especially after all that flattery, please just let us learn this particular bit of info for our early builds so our learning curves can benefit from the "learn from each other" method rather than the "Do it all yourself" method.  If you're not willing to pet puppies, why bother being here?

We thank you when you are willing to share your work and knowledge here. It makes you good folk

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I have to agree with the basic premise of this question.  I’ve read essentially the entire gas forge section, some threads multiple times and still I have some blank areas in my understanding.  I have two pages of notes and quotes of specific posts with links to them.  Still, one basic question bothers me.  Okay...a few questions... :)

   Every IR reflective material like metrikote says in the directions that it should not be applied on top of another castable refractory and yet all the directions I have seen suggest a layer of kastolite 30 and then ITC 100 or similar in a thin layer.  Is this layer for the entire inside of the shell or just the floor?

Im also curious about how people get a tight fit between the ribbon burner and the wall of the forge.

Also, is a kiln shelf a must if you follow the above directions for castable and IR reflective?

Okay, I know this is annoying because this has all been said in small bits here and there.  But conflicting ideas and cutting edge options have also been mentioned in the same threads.  It has been seriously hard to piece together a happy medium between making a solid forge and making a cutting edge forge.  I just want to make something that is proven and reliable.  I’m still unclear after many hours of reading on how my forge floor should be constructed.  This is no,demand and I’m willing to make some mistakes and learn the hard way.  I’m even happy working with my coal forge indefinitely,  

Once I struggle through the process myself I fully,intend to post my experience with an attempt to boil,down the complex issues I struggled with.  Sadly, by then, it will likely be out of date as the pros learn newer and better techniques and materials.  I think that is the dilemma in its essence.  We new guys want to make something as up to date as possible but that is a moving target.  It’s like jumping into a moving vehicle.

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If cost is no object I would use Greencast 97, or similar high alumina cast refractory for the ribbon burner, forge floor and a patch directly opposite the burner flame.  There are other options for a forge floor (like Mizzou or bubble alumina) or Mizzou can also be used for the burner, but these are compromise choices as far as I'm concerned.  Note that the forge floor should also have an outer layer of blanket insulation.

I like a minimum of two material layers for the forge body.  The outer layer of around 2" of high density (6#) 2600 deg refractory ceramic insulating blanket (sealed of course) then somewhere in the 1/2" - 1" thickness of a high temperature insulating refractory castable like Kastolite 30 (with an inner facing of IR radiator material like Plistex or Metricoat).

There have been a lot of posts discussing this.  Try the google search function on the Iforgeiron site to access them.

3 minutes ago, Lou L said:

Also, is a kiln shelf a must if you follow the above directions for castable and IR reflective

No

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To begin with, most of us recommend a refractory that we have a long history with. I built all of my early casting furnaces with Kast-O-lite 3000 (now called Kast-O-lite 30). Back in those days I wasn't even concerned with Kast-O-lite's ability to insulate, which is remarkable in a hard refractory.  Its toughness and crack resistance were what I was after. I also found it easy to do a good job with because it changed slowly from the state of green-ware  to the hardness of structural concrete, allowing me to smooth out edges by scraping them with straight edge tools. In eighteen years I have never had a singe crack in a piece of heating equipment.

I will not even compare my choice with those of other guys; I don't think it leads to helpful discussions. I would much rather hear others speak out based on their long acquaintance with a favorite product, and what they like about it; that brings out helpful information for beginners, since you need to bridge the gap from our considerable experience and your lack of it.

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6 hours ago, WayneCoeArtistBlacksmith said:

Check out the Build a Gas Forge attachment  and the Ribbon Burner attachment at the Forge Supplies page of my web-site.  

 

Actually, I think that those files are where I read about using different refractoriesfor forge and burner.  I know you mentioned which you liked for which, but I couldn't figure out where to go on your site to purchase them.  

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Has anyone tried LOUCAST?  The maker says it compares to Mizzou.  How well?

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I am looking for a castable refractory with a smoother consistency than kast o lite which can withstand the heat.  I am experimenting with ribbon burners.  I have looked around but most refractory talk is about it's insulative quality or how to mix it.  Has anyone tried sifting kast o lite?

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I've sifted it through a screen colander on a couple occasions. That's vague, I've sifted the aggregate from Greencast 97 and Kastolite 30.

I did it with the Greencast to see if I could make a smooth floor with 2 pts.Zircopax in it. What I tried was so so finish. It worked but it wasn't really very smooth and I didn't want to experiment till I figured it out. I also tried it as a rigidizer by mixing it till it looked like muddy water. It made Kaowool really stiff but I think it cut down on the insulating properties.

I sifted the Kastolite 30 for the same reason in the newest forge and it still didn't come out as smooth as I wanted. I applied it like a thick kiln wash, 1 pt. Kastolite - 2 pts. Zircopax again it worked but I wasn't happy with how rough it turned out.

I sifted the Kastolite for the second ribbon burner block. It poured much easier and finished more smoothly. However it has the only crack of the pair. It's a small crack in an unimportant place but it has a crack.

Frosty The Lucky.

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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

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Hi Dan,

"Using a mix of zircon flour and colloidal silica". 

Was this a 50:50 ratio of some other combination?

I'm interested in doing some "Tinkering".

Tink!

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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

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Hi Dan,

I can get some Zircopax (Zirconium Silicate powder) in the UK, and I've found Colloidal Silica as powder for adding to Epoxies as a thickener.

It's not clear from your reply how much or what ratio I might mix these two, before mixing up a slurry with water.  

Also it sounds like you are accelerating the hardening of each coating with heat. Is this just putting the propane on low for a couple of minutes every 15mins or so, or do you have a different method?

I'm happy to take my time and have a play, but don't want to ruin my ceramic blanket before I get to use it in anger. ;)

Tink!

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On 3/10/2019 at 10:33 PM, Another FrankenBurner said:

I am looking for a castable refractory with a smoother consistency than kast o lite which can withstand the heat.  I am experimenting with ribbon burners.  I have looked around but most refractory talk is about it's insulative quality or how to mix it.  Has anyone tried sifting kast o lite?

Harbison Walker makes a moldable version of kastolite that can be applied by hand (with gloves) or troweled on.  It can be applied smooth.  But, in truth, kastolite can be quite smooth if you use forms.  I used metal flashing (with a release agent in case) and the parts that were controlled that way came out very smooth.

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55 minutes ago, Irondragon Forge & Clay said:

Not even going to go there, we'll leave it for Frosty.:lol:

You're NOT picking up on good vibrations? 

Frosty The Lucky.

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11 hours ago, tinkertim said:

I can get some Zircopax (Zirconium Silicate powder) in the UK, and I've found Colloidal Silica as powder for adding to Epoxies as a thickener.

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/

11 hours ago, tinkertim said:

accelerating the hardening of each coating with heat

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.

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6 hours ago, D.Rotblatt said:

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

Interesting.  I used exactly this type of silica powder mixed with water as a rigidizer and it worked great for me.

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This is the thing that was confusing me a little, as numbers of people appear to be using "Fumed Silica" powder mixed with water as a rigidizer on their ceramic blanket, and heat it up to set it, before laying on their insulating refractory coat.

 

Dan, are you saying that when you have tried this it ate your ceramic blanket, or only when you mixed Zircon flour and colloidal silica powder, added water and then coated your blanket it ate the blanket?

Hmmm.

Tink!

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24 minutes ago, Latticino said:

Interesting.  I used exactly this type of silica powder mixed with water as a rigidizer and it worked great for me.

Ditto.

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Colloidal silica seems to be straightforward, but the more I get into it the less simple the whole material becomes, I believe the man is serious about the problem he found, and If we look a little  closer at the situation we may come up with another valuable onsite into ceramic interactions. 

As with powder metallurgy, size matters; colloidal particles are very small indeed.

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I know that others here have spoken about hydrophobic and hydrophilic versions of colloidal silica; I wonder if that might be part of the problem.

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I used the fused silica and powder for a rigidizer on several of my forge.  Worked great, but I only heated it enough to dry and set it.  Then I covered it with a high temp coating of the zircon and colloidal silica for slurry casting (Adbond II).  That combination works great.  In my first ribbon forge the burner points right at the wall which gets quite hot (I weld in it), but doesn't seem to be degrading at all.

Because Adbond II type colloidal is hard to obtain in small amounts, I decided to try to test the fused silicon/water/zircon against the colloidal silica/zircon to see it it would work so other people could use this kind of coating.  My test was as follows. I mixed up a batch of each and painted them on one side of a rigidizied 2" square of ceramic fiber (yes, Frosty, I buttered). Dried them with a torch then stuck them in the forge under the burner.  Within a minute, the fused silica/zircon sample ate away at the ceramic fiber when at orange heat, while the adbond sample formed a hard shell and the rigidized blanket under remained pristine.  It tried the test with varying ratios of fused silica : water : zircon and got the same result.  I seem to recall that I removed the zircon and used just fused silica/water and got the same result (it was some months ago and as it was a total fail I didn't record the results).

My conclusion is that the purchased fused silica works great as a rigidizer as long as it is covered, but when subjected to the full heat or atmosphere of the forge it melts the ceramic fibers.  Reading discussions in this thread, I believe the way it rigidizes is by melting and holding the fibers together.  My guess is that at higher temps it reacts with the fiber and just melts it away.

The whole purpose of Colloidal Silica is to mix with either a silica or zircon powder to form a slurry.  A wax mold is dipped in the slurry and then sprinkled with varying grits of powdered silica starting with layers of fine and going to layers of coarse to build up a shell mold.  The mold can be used to cast anything from aluminum, bronze, iron, steel, to ultra high temp alloys.  Obviously the Colloidal silica was developed to take very high temps and thermal shock without melting or fracturing.

Dan

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Hi Dan,

It sounds like you've done some really useful comparative tests, and following your reasoning & observations, I agree with your conclusions.

I've found somewhere I can buy small amounts of colloidal silica slurry, as well as Zircopax and the fumed silica powder, so I'm going to get some of each. As you and others have done, I'm going to use the fumed silica powder & water for the rigidising, and then use the slilca slurry & Zircopax as the hardened hotface.

Thanks for clearing up my confusion with the different types of Silica products. I feel I can source the right kinds of materials now.

I'll keep you posted when I start my new small Butane tank forge build (once I can find where I put the empty tank!)

Cheers,

Tink!

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