# Refactory Mix



## Joe (Aug 27, 2007)

Hi all, I am experimenting with high temp refactory. I am trying the refactory mix on the backyard metal casting site. It calls for cement, bentonite, perlite, and sand. Users report good results. It holds up well and should withstand at least 2,000 degrees. I made a couple of melting dishes using tuna fish cans as molds this weekend. I will test them after they cure. 
I have had trouble finding a bag of bentonite clay, so I bought kitty litter. It is very difficult to powderize even after soaking. I added a little laundry detergent to some wet kitty litter tonight. It seems to be dissolving it. Looks like it will do the trick, but I'm not sure if the detergent will effect the way the refactory bonds.
I have put the torch on some different items to see what happens. Clay sewer pipe---cracks. Terra cotta pot---cracks. Drywall/gypsum---breaks down. Cement fiber board---breaks down and melts although it holds up better than any of the previous items. 
I have a question. Would adding talc to the refactory mix improve it? It's melting point is supposed to be 1,500 Celsius. It has good heat resistance. It is easy to work with. It bonds with clay. It is cheap and available. 
I was going to add some pictures, but it looks like I am having a hardware problem....I will post some along with some kiln experiments I did this summer in the near future.


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## aflacglobal (Aug 28, 2007)

http://goldrefiningforum.com/~goldrefi//phpBB3/viewtopic.php?t=845&highlight=furnace


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## jimdoc (Aug 28, 2007)

Joe,
Lionel from the backyard metalcasting website says
he has dealt with this place for high temp refractory;

http://www.hwr.com/

They have a distribution center near me in Trevose PA,
but I haven't had the cash to go check them out.
Jim


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## Platdigger (Aug 28, 2007)

I have several bags of high temp mix of some type. Came from Hanford.
But, I am in WA and I supose shipping would be prohibitive.
Randy


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## aflacglobal (Aug 28, 2007)

Refractory Castable



Over the last fifteen years this refractory castable formula has been used to create the arch tops of five anagama kilns in Virginia and Maryland. Three arch tops are of similar size, approximately four to five feet interior height, five feet wide, and 18 feet in length. The fourth and largest arch top is about triple in volume; it spans about seven feet in width, up to seven feet in height, and is 35 feet in length. The fifth is a hybrid: a 12-foot long barrel arch in front of two noborigama chambers.

These notes are intended to share our knowledge, but obviously use of this information is not our responsibility--the actual ingredients used, the methods and quality of mixing, and the amount of water added are all critical components.

For one commercial source--which was used for the largest kiln in order to ensure completing the arch in one day--of premixed refractory castable, contact Craig Felton, Director of Technical Services, Mt. Savage Specialty Refractories, PO Box 608, Mt. Savage, Maryland, 21545, Phone (301) 264-3595.

Warren Frederick - November, 2000

[See manual e-mail link at the bottom of this web-page] 

***********************

Special thanks to Bill Knoble of Red Truck Clay Works in Chestertown, New York--one of the original wood-firers--for his initial efforts and experience in researching and developing this castable information twenty years ago. 

***********************



BASIC FORMULA

[Parts by volume, not weight; e.g., 5 gallon bucket is 1 part]



1 part + 25% Calcium Aluminate Cement -

[Do NOT use Portland; doesn't hold up to heat] 

Refcon has been used with good results; was a product of Lehigh which is now Heidelberger Calcium Aluminates, 7660 Imperial Way, Allentown, PA, 18195-1040; Phone (1-800-348-7070). One part of Refcon is the bare minimum; an actual chemical analysis varies depending on the grog size and the type/weight of other ingredients so another 25% would be useful. 

2 parts Kyanite - 

Calcined kyanite is mullite; 65% alumina; expands when fired; needle-like structure adds strength

Mined in Dillwyn, Virginia by the Kyanite Mining Corporation, PO Box 486, Dillwyn, Virginia 23936, Phone (804) 983-2043; only mine in the USA. Can use mullite or commercial variations such as Mulcoa (such as M47-100)-- trademark of C-E Minerals; various grades of 47% to 70% alumina; [C-E Minerals, 901 East 8th Avenue, King of Prussia, PA 19406, Phone (610) 337-7163]

2 parts Fireclay - 

Have used AP Green Missouri and Hawthorn

2 parts Grog - 

A variety of sizes, but large grog (e.g., 4 x 10 mesh) seems better.

+ 3 parts Sawdust - 

For an insulating castable; burns out. Add damp, well-wetted after dry mixing all other (7 parts of) ingredients.





MIXING AND APPLICATION

Dry mix 1.25 part cement + 6 parts other. Have mixed by hand/hoe in wooden trough. Can also use clay mixer for dry mixing only; we have split apart a pug mill by adding water--the castable sets up too fast and the pug mill cannot be cleaned between batches.

Get sawdust ready; try to maintain an even dampness. Add sawdust to dry mixture. Add water to obtain a firm, "ball-in-hand," plastic consistency.

One team applies the castable over a form (which is covered with plastic for good curing) while other teams continue to mix up batches of castable. We have had teams of 10 to 40 people. It is useful to complete the arch in one work session so it cements together as a monolithic unit.

Use castable like structural brick; work with it like clay. Work perpendicular to the form; create slight wedge shapes so that whatever cracking/layer separation occurs is structurally immaterial. In essence, you are really casting bricks by hand and in place. Setup time depends on the weather and the mix; minimum available time between mixing and applying is usually 15-25 minutes.

Normally we make at least a five inch thick layer of good castable. Over this another layer of "junk" castable is added composed of clay, sand, and cement. Have used: 3 parts silica sand; 1 part clay; 1 part cement; and 3 parts sawdust.

Assume 100 lbs of material are required for 1 cubic foot of castable. [So a kiln with 100 square feet of surface area would require 50 cubic feet of material to make a 6 inch thick layer, or 5000 pounds of material.] Don't figure too closely; for instance, assume materials are required for a 6" thick layer even though you might be aiming for 4 1/2"

The kiln illustrated here required approximately 1000 lbs of fireclay; 1300 lbs. of kyanite; 1000 lbs. of grog; 500 lbs. of Refcon, and a pickup truck of sawdust.. Note that Kyanite is particularly heavy, so some 30% more was required when calculated by weight.



TECHNICAL INFORMATION LINKS



An overall, detailed explanation of high alumina cements is in the September 1998 issue of Betoniek from Heidelberger Calcium Aluminates; choose <Bibliography> then <Betoniek> to download a PDF file (readable with the Adobe Acrobat reader) or a ZIP file. 

Calcium aluminate cements achieve 80% of their strength within 24 hours; Portland cement requires 28 days to develop the equivalent percentage strength. 

Technical information on concrete from QCL in Australia; can't link directly because of frames, so choose <Technology> then <Technical>

History and principles of concrete from MAST, Materials Science and Technology Teacher's Workshop, Prepared by the Materials Science and Engineering Department at the University of Illinois, Urbana/Champaign

AP Green is now part of ANH Refractories America; Acrobat PDF files on mixing and using castables from their product page. PDF listing of installers and perhaps suppliers.

Lafarge Aluminates for calcium aluminate cements

Whittaker, Clark & Daniels for calcium aluminate cements (older link with summary table) newer link to individual info sheets on three grades



Refractory castables from Able Refractory Products in Houston, Texas. A discussion about castable installation and curing. Their curing/firing instructions are:

Curing The set times on Able castables, as with all castables, vary from one product to another, but generally the time required for Able dense castables is shorter than the time required for Able insulating castables. Generally, forms can be removed from side walls after twelve (12) hours for dense castables and twenty-four (24) hours for insulating castables. Forms for suspended roofs or arches require double the time of side walls. 

Firing After curing is complete, a minimum of twenty four (24) hours after installation, castable firing can be started. The curing and firing process, once started, should be followed through uninterrupted.

Some moisture will still be present in the cast-able, so gradually bring the temperature to 225 F and hold for twenty-four (24) hours. This dries out the physically retained water. Note, rapid initial heating above the boiling point generates steam pressure within the castable, which destroys the strong bond and causes spalling and cracking. If excessive steaming occurs during this firing process, hold the temperature until steaming subsides. Then raise the temperature 25 F per hour to 600 F and hold for twelve (12) hours. Then raise the temperature 50 F per hour to 1200 F and hold for twelve (12) hours. Then raise the temperature 50 F per hour to the desired operating temperature. Hold at this temperature until the heat balance through the material is established to obtain the ultimate ceramic bond. Heat-up is to be continuous and uninterrupted. All temperatures are to be measured at the surface face of the refractory. Cooling should not exceed a rate of 100 F per hour.

Consult your Able Refractory sales engineer for proper procedures on more rigid cure out and firing schedules for unusually thick linings, and for any questions.

http://www.artistpotters.com/anagama/castable.htm


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## Harold_V (Aug 28, 2007)

Platdigger said:


> I have several bags of high temp mix of some type. Came from Hanford.
> But, I am in WA and I supose shipping would be prohibitive.
> Randy



Please note that the majority of such mixes have a shelf life, and for good reason. The agent that allows them to harden fails in time, so while you get the desired form, it is very weak and collapses prematurely. Shelf life, as best I can recall, is something like only a year. Old stock is, for all practical purposes, useless. My experience in using some that was outdated supports the claim. 

I'd also comment that anything that uses Portland cement in the recipe is a waste of time, regardless of the claims made by those that promote them. Portland cement degrades with heat----and reverts back to its original form, so you experience much the same thing with that as you would outdated refractories. 

The work involved in building furnaces is great enough that you should insure that it is not wasted. Buy fresh refractory from a reliable source. More than money may be at risk otherwise, especially if you're making melting vessels. 

Harold


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## Platdigger (Aug 28, 2007)

True, I am sure. but I believe this stuff lacks the hardenning agent.
Randy


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## Harold_V (Aug 28, 2007)

Interesting. 

I'm no authority on refractories, but if your have no hardening agents, I then question why it would harden for any reason? There are some that require vitrification, but the average furnace falls far short of enough heat to accomplish that task. Any idea how yours hardens? Do you have a trade name of the product? Curiosity is eating me up at this point. I have two furnaces planned for the future, although neither of them will be for precious metals. One must withstand the temperature of molten steel, however, so the demands will be greater than a crucible furnace for refining gold and silver. 

Harold


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## Platdigger (Aug 28, 2007)

I will check tomorrow Harold. Been awile since I looked at it. I am pretty sure you have to mix it with something else. Or, should I say I thought this was how it was used. If it turns out it is something you can use, you are welcome to it. I could even drop some by on my way to Tacoma some time.
Randy


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## aflacglobal (Aug 28, 2007)

:arrow:

Sorry i'm headed out the door, But you are correct the cement does not promote bonding this is done by the growth of the crystal structure from the Calcium Aluminate Cement. Their is very little portland cement in it if any and it is converted or burned off during curing. The amount of Calcium Aluminate Cement present is what sets the cure or harding rate.
Do not over add water or the mix will be weakened

Shelf life is 1 year tops. depends on humidity and temp at which it is stored to. I'll write more later.

Ralph


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## Harold_V (Aug 28, 2007)

Platdigger said:


> I will check tomorrow Harold. Been awile since I looked at it. I am pretty sure you have to mix it with something else.



That would certainly answer the question I have about what causes it to set. 



> Or, should I say I thought this was how it was used. If it turns out it is something you can use, you are welcome to it. I could even drop some by on my way to Tacoma some time.
> Randy



That's a very generous offer, and I'd welcome some, assuming it would work as expected. I'd even make it worth your time and effort. 

No need to wait for delivering any of the refractory. If you'd like to pay a visit, I can show you a lot of samples you might find interesting, and we can talk gold. Let me know if you'd like to do so and I'll give you driving instructions. If you drive highway 12, you are within a few miles of our address, and in the right direction towards Tacoma, so it doesn't take you out of your way. Just alters your course. 

Harold


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## Platdigger (Aug 29, 2007)

Mighty fine of you Harlod,
 I am sure I would enjoy it immensely.
I was looking at that stuff today, it is made by Resco Products. Seems like there were a tag or two when I put it there. I can call the company tomorrow to see if I can figure out the ingredients. all I have right now is the letters and #s "REF 060".
Randy


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## Platdigger (Aug 31, 2007)

OK, not sure if you could use this stuff or not, but I found out the breakdown on it today....this is it...
Chemical Analysis (%)
Al2O3 15.3
SiO2 76.7
Fe2O3 1.0
TiO2 0.4
Alkalies 0.9
LOI 5.7


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## Harold_V (Aug 31, 2007)

Judging from memory, it's not looking too good for me at this point. The lining I'd need for one of the furnaces would have to be low in silica--which is readily absorbed in iron. A high alumina content is quite desirable in that instance. 

If your material has a trade name included, or the maker is known, it might be easy enough to determine the shelf life. I'm of the opinion that your material falls under the same category as those we discussed that won't set well, if at all, after they've aged. Is it possible to provide the name of the maker, or the trade name of the particular product you have? Their manuals will usually disclose the needed information. Likely would be found online, too. 

Assuming it would set, it could well be used for a crucible furnace, which is the second furnace of concern for me. Such a furnace would be limited to a heat range under 2,200° F. , used primarily for melting copper alloys. 

Harold


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## Platdigger (Aug 31, 2007)

Sure thing, and they are online. This is were I found out what I did. It is Resco Products inc. and the name of the product is PYROFRAC 1004
I still think you may have to add a hardenning agent of some sort....not sure of course. There must be more than a ton of this stuff out there.
Randy


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## Joe (Sep 5, 2007)

Thanks for all the help everyone! I learned a lot. I tested the portland, sand, clay, and perlite mix. I put a layer about 2 inches think in the bottom of a cast iron 2 quart pot. I put the oxy-acetalene torch on some copper. It started to melt into the mix. Some small cracks developed. I'm sure the torch got hotter than 2,000 degrees. The tuna can melting dish cracked and broke apart with heat on it. That mix might hold up for a while with a thick layer in a furnace if temperature was regulated. It seems like it would make a good insulation---build up layer around some higher quality refractory cement. 
I looked at the different options. I ordered some Rutland Black Furnace Cement. I am going to mix it with 4 parts perlite and see how that works.


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## Bernie Foley (Nov 3, 2008)

Hi Joe&friends,
I use Rutland stuff.If you have trouble with the black try the buff colored
cement. I like it much better than the black...good luck..Bernie


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## n3vrs0br (Nov 20, 2008)

Is this a viable plan? http://countryplans.com/vintage_farm//foundry/Furnace.pdf

It uses just fire clay and "grog" in the liner.


mike


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