Preferred Refractories for Chamber vs Ribbon Burner

[D.Rotblatt]

1 hour ago, tinkertim said:

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

No problem!  Your confusion means I didn't explain well  Love to hear about your build!  You're the first person besides myself to use this (I've been using it for 20 years).

I'm curious, for the sake of others trying to do the same, where did you source the colloidal silica?

Dan R

[tinkertim]

Hi Dan,

I like it when someone gathers experimental evidence, with for & against examples, and gives reasoned analysis and logical conclusions.  It ticks all my nerdy engineer boxes!  

It's quite difficult to find companies who will sell smaller amounts of materials and stock in or ship to the UK. (Kastolite-30 being my biggest headache!).

Here are the [Google searches I used to find] the materials I can get shipped in the UK that I'm going to experiment with:

 

GOOGLE: mbfg fumed silica

GOOGLE: scarva en gb zircopax

GOOGLE: ulster ceramics morisol x30

 

It's not clear whether the Morisol-x30 is in powder form or a ready-to-use liquid, but as it does come in 1Litre, 5Litre, etc. I think it should be liquid.

Catch you later,

Tink!

Edited March 15, 2019 by Mod34
External links replaced with Google search terms at poster's request

[D.Rotblatt]

I never thought to check ceramics supplies for colloidal silica!  Good job!  It also states that Marisol can be used as a Rigidizer for ceramic blanket for glass slumping molds. I imagine it would work for our forges as well. 

I’ll check pottery supply places here in the USA so I can pass on that info to local forge makers!

Dan

[tinkertim]

When they talk about a colloidal silica slurry, I believe it contains more that just Silica & water, as it also frequently mentions "binder" in various slurry descriptions.

I think what confused me originally is where various products refer to colloidal silica, but some are referring to a pure dry powder and others are referring to a suspension of colloidal silica (potentially with other chemicals/minerals also included in it).  They are definitely not the same thing.

When I place an order and start my build I'll take loads of piccys for reference purposes.  It probably wont be for a few weeks though.

Thanks for the help Dan, I'll keep you posted.

Tink!

[D.Rotblatt]

My bad.  I misremembered some of the results from my eggshell experiments.  What I said works works, and what didn't didn't, but it was a little different from what I remembered.

First, the Colloidal Silica (Adbond II) used alone without zircon flour melted the ceramic blanket rather then acting as a rigidizer, so use fused silica as a rigidizer.  This may not apply to what you bought, since the colloidal silica's I'm seeing sold at pottery supply houses are for rigidizing ceramic blankets for glass slumping and such.  You'll have to try yours on a piece of scrap ceramic blanket.

Second, the fused silica/zircon mix didn't melt the blanket, it just didn't bond and form a shell, but rather flaked right off.  The colloidal silica (addend II)/zircon mix forms a hard shell as previously stated.  

My original description is on Page 35 of the Forges 101 thread.

[Mikey98118]

On 3/14/2019 at 6:42 AM, tinkertim said:

It's quite difficult to find companies who will sell smaller amounts of materials and stock in or ship to the UK. (Kastolite-30 being my biggest headache!).

I am a long time fan of Kast-O-lite 30, but purchasing problems are the hardest problems to deal with; so why not deal without? There is nothing magical about their formula. Just use another alumina based refractory and add glass micro bubbles to it; "presto chango" and you have all the substitute choice you need

[tinkertim]

Hi Mikey,

I had come to the same conclusion. I have seen sites selling many of the individual constituents, and I believe its the glass micro bubbles that make the refractory an insulating refractory.  If I can find places that will sell small amounts to experiment with, then I'll have a play.

I'll post up my findings, as and when.

Tink!

[Mikey98118]

If you can't, we used to do the same trick with Perlite; that also works quite well

[tinkertim]

Interesting!  I bought a small bag of Perlite in a garden center last weekend, to use as an insulating bed for slow-cooling of blades, annealing, etc.

Would it be up to welding temperatures if mixed with a high alumina refractory?

[Frosty]

Not going to tell him where to find bubbles, (evacuated silica spheres) Mike? The common use is in light weight concrete it's commonly available at your local sand and gravel supply or concrete batch plant. Take doughnuts and they might just give you a broken bag. Yard guys are like that you know. 

Frosty The Lucky.

[tinkertim]

Thanks for the suggestions Frosty, I'll do some local hunting.

Tink!

[Lou L]

There is a Harbison Walker outlet in England.  They make and sell kastolite, green cars, mizzou, Inswool and a number of others.  I realize the country is larger than a two hour drive but they may deliver if you aren’t close.

HarbisonWalker International Limited
Dock Road South
Bromborough, Wirral CH62 4SP
England
Contact: Erik Bachman
P: +44 (0)151 641 5901
F: 44 151-6415910

[tinkertim]

Cool!

Thanks Lou, I'll look into that.

Tink!

[Mikey98118]

5 hours ago, tinkertim said:

Would it be up to welding temperatures if mixed with a high alumina refractory?

It doesn't matter that Perlite melts at 1900 F; It does the same job that micro bubbles, or sawdust does. All three leave convenient air holes in the refractory. The only difference I see is how tidy the results are; not how practical any of the three choices are

[tinkertim]

I thought the Silica micro bubbles wouldn't melt as long as they were not on the flame face.

I guess either silica micro-spheres or voids where micro-spheres used to be are both going to have pretty much the same effect; they make an insulating refractory.

I just need time and bits to play with.

Tink!

[Mikey98118]

Silica is the most common binding material in refractories. It is a mistake to only consider melting temperatures and forget chemical interactions in refractories. Also, how small, or in this case thin, the silica surface is, which is interacting with the other refractory materials has much to do with what becomes of it during firing. I would be very surprised to find anything more than trace amounts of silica left in the interface between micro holes left from the bubbles and the alumina content surrounding them; or I could be completely wrong about this whole scenario 

In any case, whether dissolved or not during firing the whole point of these micro bubbles are in the voids in they leave behind in the refractory matrix. Perlite will certainly melt during firing, leaving voids behind where they rested in the refractory matrix.

Sawdust will turn to charcoal, and then to ash, leaving behind voids.

The desired end product is voids in the matrix, however we get there.

[tinkertim]

Hi Dan,

A question for you. What does your Colloidal Silica liquid/slurry look like?

I've got some of the Morisol X30, and it looks like a cloudy, translucent liquid. It seems quite watery, but you can feel the Silica if you dip a finger in and rub it with your thumb.

I guess I was expecting something grey and opaque. Is that what your Colloidal Silica liquid looks like?

Catch you later,

Tink!

[D.Rotblatt]

I recently bought a different brand so I have two examples. I imagine they are different based on additives. Nalco 1144 and Adbond II. 

Adbond is opaque white, consistency of water. 

Nalco is nearly clear with a slight white tint. It seems a little thicker then water. 

What you have sounds right. Test it on a little piece of ceramic fiber first to see if it works. It seems there’s lots of different mixtures for different purposes. 

To make slurry mix in  zircon until it’s like latex paint.  It takes less liquid then you think, maybe equal amount by volume. Then just paint onto wet ceramic wool with brush. 

Dan R

[tinkertim]

cool! Thanks Dan,

I was a bit worried I didn't have the right stuff.

Just waiting on the Zircopx to arrive and I'm good to go.

Cheers,

Tink!

[tinkertim]

Hi Dan,

Bits have arrived and I've been busy, and I have the Forge lined with 2 x 1" Ceramic blanket and have rigidised both layers successfully.

So now comes the Heat-face layer.

I have the Morisol-X30 Silica base, Zircopax flour and glass bubbles.  I know you suggested adding the Zircopax until you get the consistency of Latex paint, but I wondered if you had any insight about how much glass bubbles to add, to get a suitable mix to apply.

Any suggestions regarding ratios?

Nearly there.

Cheers,

Tink!

[BartW]

I think I know why this issue is US-only. 

Previously, I went to a metal recycling firm, and asked for a couple of bag of repair cement for melting crucibles; and they gave me about 100 kilos of Intoval Repa SP10 (google that  ) . 

I used it for pretty much everything that involved high heats - firepots, lining of gasforges ... and of course, making other smiths happy as trading stock.

Then I ran out of the stuff, and the metal recycling firm doesn't deal with private people anymore. So no more good stuff. After talking to a fellow German smith, he told me he just orders it off amazon, so he didn't understand the problem. Just search for "Rath Carat D 1800".

Rath Carath technical specs

So that's what I do these days, I buy it in bags of 25 kilo of amazon. It's essentially the same stuff; 98 % Al-oxide fine powder, and some stuff to hold it together. Mix it with water, and you can make smooth porcelain like white surfaces that handle 1700°C (3000° F) easily. Also, if mixed correctly, it will stick to almost any metal. Once dry, it's more like grainy white ceramic; and acts like that too. 

Doesn't even crack is you pour water on it while it's red hot

[tinkertim]

Hi Bart,

Sounds useful stuff, but as a hobbyist I cannot justify the ~£240 for a 25KG bag delivered to the UK.

I'll continue on with Dan Rotblatt's Silica investment slurry + Zircopax technique. 

Although it might not be as strong as Kast-o-Lite, but with a lower thermal mass & IR re-emissive Zircopax, it should make for a quicker & cheaper forge heat-up for a hobbyist's use.

Tink!

[tinkertim]

Hi Dan (D.Rotblatt),

Had some issues with my Colloidal Silica slurry / Zircopax mix.

I had tried to mix it 50:50 by volume, but made the mistake of adding Zircopax to a fixed volume of Silica slurry, to try and double the volume of liquid.

This gave me a mix with much more Zircopax in than I expected.  It coated pretty well for the 1st coat of the Ceramic blanket and the IFB floor as it was so thick.

The downside was when I came to re-use the rest of the Zircopax Colloidal Silica mix for the next coat, was that the majority of the Zircopax had set solid in the bottom of the jar!  So I've probably wasted ~1/3 of my Zircopax! 

Ho-Hum, at least there was plenty that would come up in suspension, so I could recoat the inside of the Forge and the top of my IFB raised-floor inside the Forge.

I think next time I will measure out a dry volume of the Zircopax to match the wet volume of Colloidal Silica slurry. Its all about learning!  

 

Here are some pics of progress.

My new Forge with a raised floor made out of IFBs, coated in Zircopax / Silica slurry.

 

Firing up the NARB to finish the curing of the Zircopax / Silica slurry coating.

 

Ramping up the gas for initial testing.

 

The raised flooring worked really well and with the whole inner lining glowing bright yellow, the centre of the raised floor was running just slightly hotter than the rest, and you could see particles that I assume are Zirconium Silicate just glowing a little brighter.  The flame also circulated really well and gave a really even heat everywhere else.

Overall I'm very pleased with the results of using the Zircopax / Colloidal Silica (ZCS) mix to coat the inside of the Forge. It is hard, but as it's not very thick I would expect it to crack a little if bashed by accident, but as you said, just patch up with a couple of coats of ZCS where the crack is and all will be well again.

I also found that with the raised floor, I had to adjust the jetting of the AMAL propane injector and the 110 sized jet was giving me too much Dragon's Breath (DB) when I turned the gas up.  Going to the default 90 sized jet gave me a more neutral flame with only a little DB.

The most useful thing is how little gas pressure I need to get the Forge up to hammering-steel temperature. The inside all radiates at the same level and the heat is really even. It might not be so useful if you need a hot-spot, but I can accept that if it runs more efficiently.

Thanks for all the suggestions and support Dan.  I'm a convert to your forge lining technique!

Tink!

ps. I've dug out an old digital camera with a decent zoom, so I'm going to see how well it captures high-heat pictures.

[Frosty]

Glowy YELLOW! Oooooh PRETTY! Looks great Tink.

Frosty The Lucky.

[D.Rotblatt]

First, that's looking great!  Lots of burner for the size of forge you have, looks like you'll be able to weld easily in that puppy!

On 5/8/2019 at 5:11 AM, tinkertim said:

I had tried to mix it 50:50 by volume, but made the mistake of adding Zircopax to a fixed volume of Silica slurry, to try and double the volume of liquid.

This gave me a mix with much more Zircopax in than I expected.  It coated pretty well for the 1st coat of the Ceramic blanket and the IFB floor as it was so thick.

Tink, answered your PM, but thought I'd put some of the same info here for others.

1) I mix the slurry by eye, using much less liquid than expected. I go for a slurry about like latex paint. I mix in a paper cup, only what I think I'll use that session.  I put in several heaping tablespoons of zircopax powder, and add maybe a tablespoon at a time of colloidal silica until it is the right consistency.  I definitely use more powder than liquid to get the right consistency. 

2) The zircon powder will settle quickly and cake on the bottom.  Even while painting it on it will start to cake.  Mix often, and scrub the bottom of the cup with the brush to break up the cake.  If you make more then you need, you can put it in a jar.  As long as there is liquid in the jar you will be able to mix it up, but the cake will be very hard and take a lot of scrubbing to get it back into solution.  Just shaking the bottle will never work.  If some of the liquid has evaporated you can add a bit more colloidal silica.

***Bottom line: mix up only as much slurry as you need to use that session, mix often while painting it on by scrubbing the bottom of the container it's in with your brush.

This is basically the same slurry mix that is used for shell casting.  I used to have it in a 5 gallon bucket.  In order to prevent the slurry from caking, a mixer on a timer is used.  The mixer must run a few minutes every 10 as I recall, and run 24/7.  When/If the power went out (or my mixer messed up and stopped) the slurry would solidify with a several inches of liquid (colloidal silica) on top of it.  I'd have to mix it back up with a drill and mixer attachment.  Took about 30 minutes of mixing to get enough of it into solution to free the propeller on my mixer.

Dan R