Crucible Stand Advice

[MJP]

New guy here. Wanting to build a foundry using a 33 gallon drum. Prefer using a combo of kaowool, rigidizer, and ITC100. Seems like the most fuel and time efficient setup. After reading numerous websites of guys building foundries, I cannot find anyone addressing the method used to raise the crucible off the floor or what they use for a floor on a foundry with kaowool lining. I've read that you need the crucible off the floor for even heating. I've read that the crucible should not be directly in the flame. If both of those is true, something must be used to raise the crucible off the floor. The other issue is that a kaowool floor doesn't seem sturdy enough to me to support the weight of the crucible and content. I've seen guys cast a table to rest the crucible, but I would think that this would compress the kaowool leading ineffective insulation.

So what's the best solution? Do you cast a solid bottom and use the kaowool only for the sides? Can insulating bricks be used on top of the kaowool bottom with a cast stand to raise the crucible?

Buying the fewest materials is preferable to save money and I don't want to start buying stuff until I have a pretty good idea of what I need.

Thanks for any help.

[Buzzkill]

My casting experience is limited, so take this for what it's worth.  Yes, the crucible should sit on something solid (normally referred to as a plinth).  The bottom of your foundry should have a hole in it for when your crucible fails inside.  That will save you a lot of time in cleanup afterwards.  Typically the plinth will cover the hole when in use, but there will be a couple small channels which will allow the molten metal to run under the plinth and out the hole in the bottom of the foundry.  Below the foundry should be a bed of dry sand or something similar to contain any molten metal that exits the foundry.  Insulating fire bricks are a reasonable solution for the bottom of a foundry if they are supported by something else.

In general it's best not to aim a burner directly at a crucible since that tends to maximize thermal shock and cause premature failure.  Try to aim the burner between the crucible and the foundry lining.  If the outer envelope of the flame happens to graze the crucible or the walls it's not a problem.

[Frosty]

Welcome aboard MJP, glad to have you. If you'll put your general location in the header you might discover how many members live within visiting distance.

How much casting have you done? Have you read about how inherently dangerous handling any molten metal is? 

In all honesty having to ask how to lift a crucible out of a melter tells me you don't have much if any experience. Like most folk new to a craft you're looking to build a melter that'll last years. It's a common beginner's mistake in all trades. 

Are there classes offered close to you? You REALLY need to learn casting from someone with experience. Casting even low temp metals like lead or zinc can put you in the hospital with 2nd and 3rd degree burns with one slip. Aluminum can maim and cripple you while burning the: shop, shed, your house to the ground. One mistake.

Just adequate PPE is expensive and a must.

I'm really hesitant to tell you how to do something so dangerous until you've taken a class or done some real research. I want to be able to look at myself in the mirror and not feel guilty.

Frosty The Lucky.

[MJP]

I found and visited a local supplier today who sold me Pacocast 28LI castable for the bottom and gave me a ceramic fiber blanket that is more than enough for the sides. Your advise to include a hole in the bottom with the plinth above makes total sense. And thank you for supplying the correct word "plinth." Now that I have the thing pictured in my mind, I know what I need. What wasn't making sense was building it entirely with ceramic fiber and there weren't any detailed diagrams on the construction of a foundry using ceramic fiber sides showing the bottom. I can bring the torch nozzle in at plinth height, so no direct flame on the crucible.

I think you misunderstood. My question was not about how to lift a crucible out of a foundry. My question was on what to use to keep the crucible off the foundry floor to avoid direct flame contact and promote even heating.

Your admonitions are appreciated and certainly not ignored. Consider that one could know how to safely operate a foundry, but not know how to construct same. Similarly, many people can safely operate an automobile, but few know how to build one.

[gwynlaredogranger]

you are referring to what is called a 'crucible block' there are two, one inside the furnace and usually one on the floor(inside the ring of the pouring shank) to place the crucible on when you use the lifting shank to place it there. great care should be exercised when transferring a crucible or ladle to and from a furnace. the crucible blocks are sold in varying sizes form about 1 inch thick to about 6 inches thick and usually about 6-16 inches wide. they are made from silicon carbide,or you can simply cast your own from a high alumina refractory. the blocks should always always be on a level surface when being used for a crucible to land on. foundry supply will sell them for standard furnace sizes.

[Nobody Special]

Yah, crucible block, or plinth.  Refractory tends to be fairly brittle, use caution.  Molten flux can eat firebrick.  And you need to have a coating over your kaowool, or you will be breathing friable bits of kaowool with every breath, nasty, nasty, nasty silicosis.

I second the seek experienced aid, unless you have a fair amount already.  I learned casting the stup...hard way, and I would recommend to anyone as something not to do. Got the funny looking scars to prove it, and glad that's all I have.  That's a very, very large home foundry.  How are you set for burners?  You might strongly consider lump charcoal, it's a lot faster, and a bit less frustrating, especially in something like a 33 gal foundry.  I would strongly suggest considering playing with much smaller melts until you get some experience under your belt.

One might know how to drive a car, but if they came in asking how to change tires, oil, or air filters, I might be suspicious, especially if the car would explode if you took a turn too fast.  Casting is really really fun, until your crucible or your mold explodes in your face or you get zinc poisoning.  It doesn't happen often, but once is enough to cause a really bad day.  We see a lot of people come in asking construction questions after watching incredibly dangerous and foolish methods from youtube.  Where ya at? Might be able to find someone experienced in your area for you, if ya like.

[MJP]

Thanks guys. I appreciate the info. I live in Indianapolis. I found a local supply house since my last post. They provided the castable refractory, a free remnant of ceramic fiber, and some setup advice. The ceramic fiber remnant was 1" x 24" x 10'. Hardly a remnant to me, but it was to them. I bought some rigidizer online along with ITC100 directly from ITC. Buying direct from ITC was cheaper than the usual online options.

My foundry consists of two cut down steel drums with a 14" diameter. I thought it was 33 gallons, but it was more like 20-25 gallons. One drum was used for the body and the other for the top. The reason I used two drums was so that the I could use the stronger top and bottom rings at the opening and avoid any raw edges. The floor is 3" of castable with the suggested hole in the middle. I also cast a plinth using a 4" PVC union as a mold and included a path for molten metal to find the hole in the floor. The walls and lid are a double layer of the 1" rigidized ceramic fiber. Both fiber and castable are top-coated with ITC-100. The lid is hinged with an angled 3' handle to allow opening without getting too close. Heat is provided by homemade propane torch similar to the examples found online with my own personal touch. The heat chamber is approximately 12" tall x 9 1/2" diameter. The foundry is mounted on a welded angle iron frame and raised high enough to place a steel bucket underneath to contain spills.

The one tip I would pass along to anyone using ceramic fiber on the walls is to cut it at an angle rather than a square cut so that the two edges of your vertical seam overlap. Having the edges overlap prevents any potential air gaps along with a more stable base for coatings that will reduce the risk of cracks at the seam.

I have fired it up and melted about 50# of aluminum so far. The good news is that it will start melting within 15 minutes from startup! I have not attempted to cast anything other than ingots while I learn. One of my melts included a radiator and ac condenser, which made for an interesting experience. It turns out that the dross included magnesium and my foundry was hot enough to catch the magnesium on fire. It didn't appear to be burning when I spooned it off the top of the crucible. However, after sitting in a steel pan for a couple of minutes I started to notice a bright light developing. It got as bright as a mig welder. I used a steel spoon to try to smother it in the aluminum oxide. Unfortunately, I only had half a spoon when I pulled it out. It was hot enough to melt the spoon. I brought it under control with some sand.

Another tip for pouring ingots: My first pour was into a brand new dollar store steel bread pan. The aluminum stuck to the pan! I spent 30 minutes with pliers ripping the steel off the ingot. Before my next attempt, I used a propane torch to burn off whatever coating was on the pan. I then carbon coated the pan with my acetylene torch sans oxygen. The ingot slid right out on the next pour. Not sure if one or both steps were necessary, but that is what worked for me.

Pictures will be posted once I am satisfied it is done and safe.

Some questions did arise during my test runs:

1. There is about a 12"-18" flame coming out the top of the foundry when the torch seems to be at its peak. Is this normal?

2. The torch will flame out if I go to maximum immediately after lighting. In order to get to maximum, I have to do it slowly and not close the lid too soon. It seems that the heat inside the chamber helps the torch function better. Could this along with Q1 be a sign that the flame is oxygen starved?

3. I already accumulated about 5-8# of dross, which contains a significant amount of aluminum. I'd like to reclaim it, if possible. Is a mixture of NaCl & KCl the best way to separate the aluminum from the dross? Is there a rule of thumb on how much to use and when to add it? I am using a steel crucible for aluminum melting, if that matters.

[gwynlaredogranger]

ok so its called a 'blast furnace' NOT a foundry an foundry is where the blast furnace lives along with the sand line and the rest of the tools. it drives me insane when people refer to the blast furnace or just the furnace as 'the foundry' so get your terms straight! (hahah pet peeve that i see more and more online these days) the flame starts lean and then can get rich, the prpane torch might work but is totally inefficient and lacks the proper stochiometric balance. you need air.

[Nobody Special]

Good evening,

That's a  considerable amount of aluminum.  Not sure what you're using for a crucible, but general rule is preheat everything, furnace, mold, stock, etc before using.  Cuts down on those nasty steam explosions.  And yes, despite the stupid youtube videos, they absolutely do happen.  Also, aluminum is kind of funny.  With the pure stuff, sometimes the slag goes to the bottom and sticks to the crucible. And it eats some crucibles, much shorter life in a steel crucible for one.  Not to mention you get inclusions from the iron scale.  I usually used to use either crushed shell as flux, or charcoal, and charcoal was easier tell the truth...especially after I put some CaCl in a forge to see what would happen.  Turns out a forge gets to limelight temps just fine.  First time I ever got a welding burn forging.  Reducing atmosphere and lids are nice for cutting down on slag too. 

I dunno, one to six ratio seems kind of high for slag, I never was able to recover a lot, but usually didn't end up with that much either. Are you fluxing?

Flame - easiest is post video or at least pics.  Sounds like you're having "dragon breath", but hard to say without seeing it.  Could be burner set up, mix, too much pressure, or not running with a proper venturi. Important to adjust everything with the burners installed.  With them out of the furnace, completely different back pressure.  Venturi or too much pressure would be first guess. 

Might look up Sculpture Trails, in Indiana, not sure how close, and I know the Indianapolis Art Center has iron pours sometimes, might be able to point you towards other casters.

Oh yes, and for ingots, angle iron troughs, or sand cast will be a lot less frustrating than muffin tins.  Sand cast is what I prefer, but honestly, I switched to forging 10 years ago and have done very little casting since.  Favorite now is to inlay pewter into a handle.

[pnut]

3 hours ago, Nobody Special said:

general rule is preheat everything, furnace, mold, stock, etc before using.  Cuts down on those nasty steam explosions

Yes indeed, nothing like an expanding vapour explosion to ruin an afternoon. Be careful. Also not pre heating the stock can cause it to do some other weird things.

Pnut

[MJP]

NS:

I have not used flux. I'm using a spoon to stir it a bit to bring up anything stuck to the bottom followed by skimming the top. The ingots look good to me, but I am sure there are impurities. My thought was to get something that could be refined further in a future melt when I am ready to make something. It's not fuel efficient to melt the same metal twice, but this is part of my learning process to break things into smaller steps to see the results of each step. Fluxing and degassing have been left for future investigation.

It seems like there are a lot of flux options. I need to find a list of fluxes with uses explained. Perhaps a different flux would be used for recycling a radiator versus a cylinder head. More research is needed.

My perception of the flame is unburned gasses are exiting the furnace due to a lack of oxygen. The gasses burn once it exits. Since the furnace is getting plenty hot, I have to conclude that I could use less fuel. There is probably a formula to calculate the ideal pressure based on the size of the orifice and the size of the venturi. Pressure adjustments don't help. Lower pressure makes the flame unstable. Would a smaller orifice at same pressure be worth testing? Or, a bigger orifice at lower pressure? The draw of air would seem to depend on gas velocity, so I would think a smaller orifice at the same pressure would increase fuel to air ratio.

7 hours ago, Nobody Special said:

Might look up Sculpture Trails, in Indiana, not sure how close, and I know the Indianapolis Art Center has iron pours sometimes, might be able to point you towards other casters.

I live 1 mile from the IAC, so I will definitely check it out. Funny how a resource so close can be overlooked.

[Nobody Special]

Depends on a number of things, as I said, if you can post pics, easier to tell, some of the propane forge guys will be able to tell you faster than me.  It's getting hot in the furnace, so I assume you have fire in the furnace.  If it burns almost entirely out of the furnace, you can count on overpressure, and venturi issues.  You'll get some flame out the top a lot of the time regardless, dunno, can't see your set up.  The point of the venturi is that it allows the gasses to slow and mix as they exit they burner, if they don't, then the furnace acts as your venturi, which works poorly.

Common easy fluxes include crushed shell, and charcoal.  They make a chicken feed additive that adds calcium and is mostly crushed shells.  I used to use borax too, but I like it better as forging flux.  Silica sand and dirt dauber nests (yes really) work well for forging, but I have no idea what they would do in a crucible.  I would think the sand at least would make weird inclusions.  Aluminum needs either a lid and reducing atmosphere, or flux, or both, or you'll lose a bit.  It oxides extremely easily.

[gwynlaredogranger]

i posted a reply about your mixture and stochiometry, if you buy ingot you dont need to woory about flux or gasses, unless youre pouring out castings that need to be certified and x-rayed, which you wont be anytime soon. you need to build a real burner system if you ever want to melt other metals.

[Soar2c]

On 9/26/2019 at 11:19 PM, Nobody Special said:

...Molten flux can eat firebrick.  And you need to have a coating over your kaowool, or you will be breathing friable bits of kaowool with every breath, nasty, nasty, nasty silicosis.

I second the seek experienced aid....

 ...until your crucible or your mold explodes in your face or you get zinc poisoning. 

...  Where ya at? Might be able to find someone experienced in your area for you, if ya like.

Nobody Special: 1st and foremost, you're most definitely Special, cause i know i am  and together, as an entirety, we are 1. Thus proving you are Special :-)

 Ok now, just wanted to see if that offer extended to others as well about seeing of someone may be local? Id love to network with someone close that has experience, etc.

Ive been self teaching everything there's to know about minerals, ores, vms, chemistry, classify, concentrate, chain mill..sluice..and blue bowl diy builds, smelting builds, roasting builds, fume hood builds, flue gas condensate, nox, sio4, sulphides, oxides, smelt, cone mold, welding, slag, dross, matte, button, electrum, cupelle,  Flux recipes, assay calculations, crucibles, refractory material, plinths...

 

Like wholey moley! Humbled and thankful  but right now im ready to prepare the charge. And once that gas is ignited, id love to know now that this way or that way is much easier and perhaps no near death or dismemberment chain of events happen, and the tiny little tricks that get shared at this point is   >=   the thousands of hours of a very inefficient self educated attempt to learn just the very small scale portion of this process. It is the catalyst to finance my entrepreneurial empire. Ive sacrificed, endured timeframes only very few are still alive who know the that. And ive been humbled never to allow any of this to ever be used in excess for a greed stricken motive. I have been lead to the water, it was up to me to learn how to drink it and not get sick. 

 

I surely cant afford to repay the universe by creating my own demise based on ignorance, or the demise of innocent, indirect affected neighbors. 

 

Any kind of knowledgeable resource would be a Godsent at this point. Pa...eastern central. Sch co. Pville shhh.

[Frosty]

Soar2c: Normally I welcome folk to the forum and suggest they add their general location to the header so they have a chance of meeting members in person.

However, reading your first post leads me to think you aren't connected to reality well enough to do any of this stuff safely. I say silly things but as jokes and I have a good idea of when to stop pushing the set up and drop the punch line. Not seeing a punch  line leads me to believe you think the drivvle you just posted is somehow relevant or consequential.

Unless you're rattling Nobody's cage and haven't let us in on the joke you need to find something to pursue that doesn't include, hot, hard, sharp, heavy or powered. 

Honest I don't want to dis or drive people off but I'm seriously concerned about the safety of you and those around you. If you talk like that in person I wouldn't let you in the door of my shop.

Please let us in on the joke, you may have pranked me a good one and I love a good laugh, especially when I'm wrong.

Frosty The Lucky.