Aluminum melting

[unfy]

Crucible tongs / rod thing.

The concept was based off of the paint can furnace video I linked on first page.  I've seen videos of other folks who use eye bolts and try to hook rod hooks through the eyebolts - but that never seemed all that great to me.  Even in one of the videos, the guy only hooks one of the eyelets while on the other one the rod is hooked under *under* it and slips out later.

First pic is pretty much what I got now.  I don't have the lower eyelet for hooking to lift the ass up to pour... but that's not the point.

The second pic is the same, but I horrendously drew on a suggestion of the bends I've talked about.  With hooking from the inside of the crucible - if you attempt to tilt the crucible on the holder thing, you bump into the edge of crucible with the long straight part of the rod.  I assume with the bends suggested, you wouldn't have to tilt the holder rod so far forward during a pour.  Kinda needs more pics to explain, but.... maybe you get the idea.


Since I've gone through a few crucibles, perhaps time to discuss dross / detecting failed crucibles.  Aluminum dross is far different than lead, mostly due to how light Al is and how rigid it cools to.

With the soda can source, the dross is fairly light, kinda 'burnt/expended wood' in a way.  The Al doesn't necessarily just "fall through it" like lead does It will try to, but it's weight makes it not as forceful about it.

Due to the heat, it's got a weird texture, too.  Kinda like a rubbery muffin.  Or bread maybe.  It's very light, very sproingy too.

When there's a huge blob of it down inside the crucible surrounded by molten Al and you're using spoon or something to get stuff out - it's got a very jello like look & feel.

When a crucible has failed, you've basically got a pot full of really hot dross.  It kinda acts like the jello.  When you try to press into it with spoon or whatever - it kinda acts like a wet stack of card board or a wet phone book.  There's not a whole lot of give like there would be if it was floating on top of Al.  Nor do you feel it kinda breaking up as you make it " V " as ya press into it (if it was in Al, that is).

Obviously there not being as much in the crucible as you think there ought to be is a no brainer

Al dross / flakes are quite sharp and can be surprisingly rigid.  Just something to think about.


Lastly, and off topic.  An ex-coworker came by, and we've both noted the smell of pineapple when melting cans.  The sugar, maybe ?  The cans in question are all soda cans.  Pepsi, no name 'cola', and rootbeer.

I'll re-iterate that this furnace / crucible setup really prefers uncrushed cans.

[unfy]

A second look at the crucible while explaining stuff to coworkers (who are interested as well)...  we were all in agreement the failure was exacerbated by how I was grabbing the crucible with grill tongs etc.  We'll work out a new system before the next melt.

The furnace and lid are very empty sounding.  Kinda like old bread heh.  And no, they don't have the 'earthen crucible' ringing sound to them.

I dunno if I posted this before or not, but the off center air inlet pipe really worked out well.  It was definitely whipping the flames around the crucible with that 'swirl' folks talk about.  So that's a huge suggestion / plus / change from the video.  While other builds all suggest it, having actually seen it in action, I concur even with charcoal as a fuel source.

Heads up about the air gap.  I was originally using a tiny blob of aluminum to hold the lid off the furnace for air movement.  It melted heh.

And about the handles on the lid.  It's obvious, but yeah - they get f'in hot!  Everything was cooling for like 30-45min and the U bolts still burnt me when I tapped them.

[unfy]

Sadly, the two crucibles from coworker won't work.  He was in a rush... they don't even hold water.

I dunno if I'll attempt stuff Sunday or not.


In other news, was looking at the furnace and lid.

Lid's cracks seemed to have gotten worse.  It also had a "feel" between pound cake and angel food cake.  Decided to flex it gently just to see if I should even remotely trust it or not.

It crumbled heh.  (first pic).

Looking at the pieces, there was a color difference between really hot and not hot areas.  See the second pic.  I post processed the picture just a tad to increase the color saturation a bit (the color difference is more pronounced than original picture showed).

Ran to menards, grabbed another plastic pot pan thing, and mixed up a new lid at 10PM heh. (last pic)

[unfy]

Oh yeah.

Picked up some fire place tongs, a couple flat furniture braces (to run bolts through to make a stop point so i can't crush crucibles).

Also grabbed a 50lb bag of 'resco goldart' clay from the paint / ceramics place near 84th/78th and Harrison in La Vista.  It was $20.  It's prolly not quite what I want, but it'll do for experimenting probably. 

As far as "what it can do", this seems to be a relevant page:

http://digitalfire.com/4sight/material/goldart_198.html

The above has an boogie woogie amount of cursory information about a lot of clays.  I'd suggest a bookmark.

[unfy]

Coworker redid the two crucibles.

Melting today.

Eyelets help a lot for control and stuff.

Not keeping count for can turn over etc.

Just a quick pic .

[unfy]

Welp... next melt after the pic had a blow out.  I really should start to go with my gut feeling on if the crucible is fine or not. 

Everything is cooling down atm.  I'll note that after I decided the crucible was failed - poured out the contents into 2 mini muffins.  Started picking charcoal out of the furnace.  Even after 10min of killing the oxygen and leaving it open and having removed a bunch of charcoal, the AL inside was still molten.  Which means as a furnace material, the PoP and sand is doing okay for AL.  Oh, and the mini muffins were glowing red / stayed molten for a long time too.  Soooo yeah, that thing was hot.

Will wire brush and take more pics later... but an initial glance seems to show a hole opposite of the eyelet in the wall of the crucible.

Taking shooter up on his offer to look for a crucible seems to be the logical next step.  Might look on ebay for chinese crucibles / tongs as well.

Will also eye ball propane furnace builds with more proper clay etc.  Charcoal has been great as experimentation, but I'd like to move on to something cleaner as well as easier. add: consistent

Some other thoughts: did the charcoal get way too hot ?  I know folks say propane gets hotter, but when it's "gettin it", charcoal seems to really be abusive heh.  I have done some "gently scrape the sides with stainless steel spoon" stuff as part of getting rid of dross/slag.  Is it possible that I'm taking crucible material with it when I do this ?  I know steel crucibles will flake with AL temps and contaminate the AL - is it possible that even though I'm not putting any pressure on the wall when doing my scrape, that I'm making it worse ?

To repeat last post: eyelet is ****ing awesome for pouring etc.

To repeat a comment earilier: the offset air tube for swirl flame action is awesome.


I'll be doing more tomorrow.

Even though you're wearing welding gloves, be aware that if you cook them, they'll get hard / rigid.  Especially at the seams.  I've now cooked 1.5 "right hand" gloves heh.


First pic below shows a crack that has developed in this 'new second lid'.   Everything seems fine, though.  Not entire sure what that thing line originating from the bottom is.  I'll eye ball things more later.  Lastly - the U bolts have started do discolor.  Different gloves ? heat ? I dunno.

Second pic shows the crack as well , but more importantly a peak down into the chamber.  There's a jet of slightly yellow flame roaring out the vent hole that you can't really see.  The "laser" looking things would be flying embers.  The crucible was probably already failed in this pic, btw.

edit: forgot to attach pics

[unfy]

Been melting more today.

The changes:

* well, the lid broke cleanly in half when i lifted it this afternoon before getting started.  since it's a clean break with no other cracks, i'm still using it.

* using a chunk of fire brick as a plinth beneath the crucible (score and break kinda like glass or plexi ... it does but doesnt work lol)

* when removing dross / slag, i'm only digging straight down into the crucible, avoiding the sides.

* on my second melt, I just kept adding cans, letting them stack without caring too much.  did one clean and then just stacking them again.  furnace and crucible all had that nice red glow so i just kept stacking.  I'd gently push the cans down into the crucible to keep making room.  Particularly, i'd try to take my crushed cans in a <> shape and push them spikey end down.  Avoids the wall and I can stop before getting too far down.  Towards the end, a nice pool of AL was formed and I was able to more or less just push cans into the pool repeatedly (much like dealing with molten lead and feeding small ingots).

* dumping the second melt, there was a whole bunch of crud at the bottom of the crucible ... on the reheat i'll clean it up a little bit, but not much.

Pics later.

[shooter]

 it sounds like you are taking what you are using for a pot out and pouring it into the molds, ever think of using a ladle and dipping it out? I would think that disturbing everything to take it out might be hard on stuff

[unfy]

I don't doubt that the thermal changes are prolly causing problems.

Using a ladle is probably not really gonna work.  While lead has a high specific heat / density - aluminum cools so quickly that it's just not likely to really work.  That said, does the stainless spoon I use end up glowing red ? Yes.  The little bit of flat stock I use for poking / skimming ? Yes.  Could heating the ladle to red hot possibly help ? Maybe.  I really don't care to try to ladle 1400F liquid, though.

Coworker wants to try slitting the exhaust pipe down the middle and wrapping it around another section of pipe.  I dunno if it's really gonna help, but it might... so why not.

Charcoal touching the crucible probably aint helping.  Using really dirty / crummy cans probably aint helping.  The slag/dross/whatever-the-****-its-called does like to create a jellied sponge like material.  This will stick to itself and to the crucible walls.  Who knows how many layers of crucible flakes off with it when you break it off a little bit etc.


Don't have much on pics.  Just gonna show the cracked lid after it was used.  I'll make another lid some time this week.  I'll include some wire mesh this time to see if it helps with strength.

Crucible failure was along the walls again.

Using a plinth seems to have really helped.  The stable base for the crucible while the charcoal crumbles is alright.  Due to the refactory and such of the furnace - there's also not a concern about applying direct heat to the bottom of the crucible like the double coffee can furnace.  This also means the base of the crucible isn't necessarily swimming in charcoal dust as time drags on.  The stable base means it aint leaning to one side and all of that jazz.

After each melt, you really wanna take the big burning chunks of charcoal out (and save) and dump all the dust / sand charcoal.  Then repopulate the furnace with old hot charcoal and throw more on top of it.  Billows / air powered charcoal does burn quickly .

Expect a 'normal large' bag of charcoal to last 2, maybe 3 melts.  At least, when doing cans.


So far, doing cans has been interesting as a learning experience.  I really don't suggest doing it as a full time source of AL though.  It's so dirty... such a hassle, etc.

Oh, Sunday's melts yielded a little over 2.5lbs of aluminum, including the puddle recovered from the bottom of the furnace after failure.


I've got almost everything to build a rammed up / harder furnace.  As in something for propane usage.  Gonna double check some dimension suggestions and buy some air ducting for the outside shell.  Yes, air ducting as a crucible or anything inside the furnace is bad because of zinc fumes, but with enough refactory the outside doesn't get that hot.

When I do that build, I'll keep pictures posted here.

Charcoal has been great as a 'get your toes wet', but I'm ready to move on.  So yes, I do suggest the pail furnace as a first go.


That lid picture ... actually... it won't let me upload it.  Or ... will it ? Forum is hating me atm...

[unfy]

It'll be time to try this again. 

I've been saving up diet soda cans over the winter, etc heh.

I have the materials to build a "more proper" furnace from last fall.  Just need to decide on final dimensions.  This will be a propane fired furnace.


Crucible is still a curious question. 

Graphite crucibles aren't terribly expensive from, say, eBay (even those in the USA etc). 

I've found slightly better prices on steel pipe, but still nothing "great" for casual tinkering.

I have grabbed the cheap $70-$80 flux core wire welder from horror freight - as well as parts needed to turn it into a DCEN welder instead of AC.  Final piece arrived today - so hopefully I can get it converted over the next few days.  Note - I'll have to consider myself a complete noob and starting from scratch when it comes to welding heh.  Been far too long.

Does the crucible really have to be round ?  Sure there's strength to round, but ... ?

Also, when moving to propane, would exhaust pipe actually work out fine ?

blah blah blah blah blah.


I've also been building a cheap CNC machine as a 'toy' ... so ... my time is rather split between work / a bunch of projects heh.

[unfy]

Made it the April Gretna breakfast yay!

Been working on some of the last bits of the 'first go around' mechanical build of the CNC.  Needed some 4 1/2 - 5 inch 1/4 bolts so ran off to hardware stores.

While checking things out, decided that I would pick up the supplies to attempt to build a simple propane burner.



I would almost call this the "earliest evolution" of simple propane burners, but it's not.  Probably not at least.

Anyway - parts that I'm aware of:

* 1 x 3/4 x 1 black iron T fitting
* 3/4 nipple, 6 to 6-3/4 long (sch40)
* 0.035 mig welder tip
* 1/4 compression to 1/8 MIP fitting (LFA-22)
* 1/4 compression to 1/4 MIP fitting (LFA-23)
* a 6-12 inch section of 1/4" copper pipe
* optional 3/4 to 1" flare (black iron)

Tools that I'm aware of:

* A drill press would be suggested.
* #3 drill bit and 1/4-28 tap (mig tip)
* 11/32 drill bit and 1/8 27TPI NPT tap (coupler that goes in the back of the T)
* File (if the mig tip is too long)

The 1/8 27TPI NPT tap can be hard to find.  The $40 tap/die kit at menards has one.  The $100 kit from home depot has one (I think).  Dunno about lowes / horror freight / etc.

The youtube video suggest the burner doesn't burn right in open air without a flare.  I've seen the 3/4 to 1" used as a flare in other burners even though it's not quite 'perfect'.

YT video also says the burner tube should be 6-3/4" long.  I grabbed an 8" nipple to cut down (if necessary) and a 6" nipple to try using with the make shift 'flare'.


I also grabbed some propane hoses and a 'high pressure' regulator from Menards (seems home depot on 84th in la vista didn't have any).  The regulator only goes up to 20psi - and it's suggested to hit up some welding supply stores to grab one that goes to 30psi... but for my small foundry, 20psi should be more than enough (I assume).

Even if the burner is a failure, I'll need the hoses & regulator for a pro-built burner (there's some really nice looking ones out there for $100-$150).


addenum: 

Corrected and clarified tap sizes. 

Added 1/4" copper pipe to list.

Added second adapter for the 'other side' of the copper pipe to list.

Most burners have some kind of valve near them for a quick safety thing.  I'm not entirely sure if a generic valve would work fine or if it needs to be a special type etc - so I'm just omitting it 


Grabbed a fresh 20lb propane tank in preparation for a burn test

Z axis on the CNC is being a pain in the ass. GRRRRRR.  I'll be re-making the carriage nut for a THIRD TIME.  After the CNC goes together today (it better, damnit), I'll get the burner built.  I should have some spare 1/4" copper pipe left over from the copper plating days.

[unfy]

First run of the burner attached below .  Should be able to just barely see a tint of blue on the business end of it.

If anyone sees anything wrong / safety problem let me know!

images are broke, so here's an imgur copy of it:




The assembly I took in short:

Pilot hole the T, follow up with 11/32nd drill the T.

Tap the T with 1/8NPT-27.  I had to use a 3/8 bit to slightly countersink the hole so the tap would bite.  Filing the hole / T flatter would prolly work as well.

#3 drill the 1/4 compression -> 1/8th MIP adapter.

Tap the adapter with 1/4-28.

Install mig tip into newly tapped 1/4-28 hole - run it all the way down so it sits flush.

Install mig tip + adapter into the newly tapped T (mig tip points inside the T, of course).

Attach about 6" of copper pipe to the compression side of the adapter in the T.

Attach 1/4" compression -> 1/4 MIP adapter to other end of copper pipe.

For me it's then copper pipe adapter -> 1/4 MIP/NPT hose -> 20psi regulator -> tank.

No, I do not have a pressure gauge.

Seems to work fine.  Flare changed colors due to heat etc.

[unfy]

Here's the burner at night.

Also: shortened the copper pipe and got the 'oh ****' ball valve installed.

Hope to get the furnace body and lid built this weekend.

Also hope to get the welder modifications done this weekend as well... we'll see.

CNC might get more done too.  So many projects, so little time ._.

[SS_N_NE]

Always get a kick outta these posts since I have done a lot of similar tinkering.  Have a paint bucket furnace sitting in the garage somewhere.

For a crucible, I have used steel pipe/tube with 3/16 wall and 1/4 plate welded to bottom and made tongs to fit. Hot things are just soft and need good tong to reduce stress....even on the red hot steel. The steel will contaminate aluminum...but in a lot of cases it is not a real problem and didn't seem to hurt any cast projects I made. There were usually few inclusions since a lot of stuff was cleaned off with the dross or just didn't follow the pour or floated out of the part. Round pipe works since it doesn't have corners for the dross to stick into....your concerns on using square...didn't work on my attempts    It is just easier to use round pipe since cleaning off the dross is easier and pour direction is anywhere instead of a corner.

Didn't catch why you are using pop cans. The resulting aluminum is just scrap.  Aluminum from previously cast items like transmission cases, cylinder heads, etc. will have better casting properties simply because it is a already figured out casting alloy. Aluminum is often referred to as "alloy" simply because it is rarely just "aluminum".  I know this is a kind of elementary statement, but if the intention is to make sand castings at some time, a casting alloy will greatly ensure success.  I worked in an industry where there were a lot of scrap to play with and found salvaging cast items just eliminated a lot of wasted effort.

Great part is that I started my attempts at aluminum casting via a booklet, the internet has since opened way more information than I ever had access to.

[unfy]

Welder project is on hold while I figure out a few things.  The capacitors won't fit in the existing case, and so I need to decide if I'm gonna build a side car to bolt onto the side of the welder to hold the DC stuff, or just try to resell what I've bought and pick up a $180-$200 welder that's already DC etc heh.

Anyway....


Furnace rammed up.  It's ugly.  Which is fine.  First time doing it it, and not using something all that sturdy for forms etc.

I used the refactory recipe from backyardmetalcasting - which is more or less sand, perlite, portland cement, and fire clay.  So far, seemed easy enough to work with.

I did make a few bone headed mistakes.


I started off by assembling the lid.  Put some 8-32 2"'s in the seams of the ductwork to keep it together and as rebar kinda.  Garage door handles with some 1/4 2" bolts.




the body assembled.  more 8-32's and garage door handles.  ran around about 1" from the bottom (it's upside down in the pic) to add some extra 8-32's as support. decided to not have any legs on the furnace.




blurry pic, sorry. sitting in a former.  the former is for 12", so I've got some cardboard wrapped around furnace body as well.  a 1.75" hole was drilled in the side for the burner pipe.




showing these out of order.  rammed up the lid last. but need to show some mistakes and those will be in the next post.  used one of the left over 3" pvc pipe cuttings from copper plating days as the vent hole.  I'll assume the 3-3.5" hole will be enough of a vent.




Now for some of the bone headedness.  I decided to use a 6" round piece of duct work as the inner chamber size / form thing...

And I kinda forget about putting a second former up higher so that the entire height of the body is kept roundish.

Here's the body / base rammed up.




And here's looking inside of the thing.

Yeah, that pipe is gonna make it kind of difficult to remove the ductwork without destroying everything.  Sigh.




Managed to get it removed without too much hassle, actually.  Pulling the seam towards the middle gently managed to get it to break the seam the entire length.  Then continuing to pull the seam towards the opposite wall - it pulled away from the refactory / rolled in on itself a bit.  Some wiggling got it free from the pipe.

The center bit that was near the duct work was a bit higher than the rest, despite my efforts to level everything off before hand.

And look at that round hole (rolling eyes). And how centered it is (more eye rolling).




And the inside with the duct work removed.  Not bad \o/.  Dunno if the pipe sticking that far into the furnace chamber is going to be a problem or not.

Drainage stuff is visible at the bottom (it'll burn out, although i'll prolly push the PVC out ...)




Hey look.  Some of the spacers I had planned on using to keep the center duct work .. well... centered.

I also didn't fill the center duct work with sand like I had planned to.  Oops.




Now it sits for a week to cure.  Hope to fire it gently next weekend.. maybe even to the point of getting a melt in (we shall see).

[unfy]

Always get a kick outta these posts since I have done a lot of similar tinkering.  Have a paint bucket furnace sitting in the garage somewhere.

Then pipe up with any obvious 'duh' things I'm missing

For a crucible, I have used steel pipe/tube with 3/16 wall and 1/4 plate welded to bottom and made tongs to fit. Hot things are just soft and need good tong to reduce stress....even on the red hot steel.

shooter's offered to have us dig through his scrap iron pile to see what we can come with.  I can prolly hit a local welding shop.... etc.

I should try to find a scrapper that would let me walk the yard looking for ferrous material to snag.  If such a place exists...

The steel will contaminate aluminum...but in a lot of cases it is not a real problem and didn't seem to hurt any cast projects I made. There were usually few inclusions since a lot of stuff was cleaned off with the dross or just didn't follow the pour or floated out of the part. Round pipe works since it doesn't have corners for the dross to stick into....your concerns on using square...didn't work on my attempts    It is just easier to use round pipe since cleaning off the dross is easier and pour direction is anywhere instead of a corner.

I've heard about the contamination - haven't actually gotten to the point of casting anything in sand yet, though.  Been just making muffin ingots.

Have seen some crucibles on ebay that aren't terribly expensive - but the tongs for them are like really expensive.  I imagine they're not too difficult to build out of flat stock, though.

Didn't catch why you are using pop cans. The resulting aluminum is just scrap.  Aluminum from previously cast items like transmission cases, cylinder heads, etc. will have better casting properties simply because it is a already figured out casting alloy. Aluminum is often referred to as "alloy" simply because it is rarely just "aluminum".  I know this is a kind of elementary statement, but if the intention is to make sand castings at some time, a casting alloy will greatly ensure success.  I worked in an industry where there were a lot of scrap to play with and found salvaging cast items just eliminated a lot of wasted effort.

Doing work with cans just to get experience with all of it.  They're more or less a free source of material to work with.  As mentioned - I've not done any real casting with it, so look forward to fighting with it in the future.  I appreciate the heads up that the closer to 'pure' AL that pop cans are will cause possible issues later.

Great part is that I started my attempts at aluminum casting via a booklet, the internet has since opened way more information than I ever had access to.

Indeed!

And hopefully this thread is helpful to others as well.

So far what I've learned: it's not too difficult to melt metal.  The crucible is of all importance, though.

I'm curious if the burner I'm using needs some choke mechanism added to it.  Won't know until later.


Furnace continues to cure - hit it with another light spray of water when I got home from work.  Flipped the lid and rotated furnace body on it's side so as to expose the sides that have been on garbage bags the entire time.  In the morning I'll stand it back up, maybe even put the lid on it with cardboard separating it.  I will prolly get one more spray in the morning and then leave it alone from there on out.

I have some concerns about the build.  Dunno if I got the refactory wet enough.  It was more or less on the slightly too wet side of casting sand.

[SS_N_NE]

The steel pipe crucible will work OK for small and less significant parts.

A carbide crucible will not contaminate the aluminum alloy but are fragile. The tongs have to be a very good fit so the red hot crucible full of molten metal doesn't get crushed or otherwise damaged by handling and dump the hot load. Tong are easy enough to make, just have to fit well, and lock in a hold that doesn't squeeze the crucible.  Eventually if you start green sand casting, you may be fluxing, which is a real corrosive process to a steel crucible and is more likely to put ferrous contamination into the aluminum.

Although pop cans are available....it takes a lot to make a small amount of metal....and that metal will not be very usable for casting...just doesn't have the right composition/alloy.

Something like a junk transmission case will yield a lot of casting material. Usually can be found laying around or bought cheap from someone on Craigslist wanting to be rid of the junk. The case can be put on a pile of wood and the wood burned to heat the case. A hammer can be used on the hot aluminum to break off chunks fairly easily (at the right temperature) that can be put in your crucible. Not melting the case, just softening it up a bit. It will be sort of crumbly when hot enough.

The refractory in an oven is a lot like casting sand, you only want it wet enough to hold the materials together while being formed.  After a bit of drying time, you make short runs of heat in the oven to drive out any remaining moisture. Once completely dry, the oven is brought up in a few cycles to operating heat which will ultimately vitrify the refractory sort of melting it together into a porous glass-like state. Each time you heat up the oven, you will need to go slow at first to drive out humidity it collects. If heated without driving out the moisture (from build or air) the heat will steam the water trapped inside the refractory and pressure will blow out chunks of the refractory or turn it crumbly. The effect is usually referred to as spalling.  Sometimes spalling can be fixed somewhat by troweling some refractory back into defects...but spalling is best avoided.

I have plans for an electric furnace...but never went that way. I now generally machine things from billet aluminum.

[unfy]

Crucibles:

This weekend will be the first couple heatings of the furnace.  I may attempt a melt, I dunno.  I plan on attempting to weld up a crucible but we'll see... time may be against me, etc.

I did order a graphite / salamander crucible off ebay.  It's a #4 A shape, which is big enough to drop cans into.  Will be making my own tongs for it.  Part of the "gonna do it eventually anyway, might as well just get one now" ...


I've gathered up a fair amount of ingotized pop cans.  Just looking at how it poured into muffin tins and how the failed crucible stuff looks - yeah, I can see it not doing so well for casting or serious work.  Granted, I did not flux nor degas it when pouring into muffin tins etc.  Not quite sure if can be alloyed with something 'at home'.  It's been useful as a learning experience, at least.

By your description of how wet the refactory should have been during the ramming process, I think I hit it on the head.  Grab it and squeeze - it holds it shape and breaks cleanly.  And while ramming it up, the 'spray' / 'excess' did act kinda dry, but still would clump if squeezed.  Sooooooo I'm far less nervous about things now.

I am aware of the slow starting heat, and pre-heating any metal molds ya might use (ie: muffin tin) to drive off moisture.  I should find that video of a couple high school or college kids that try to pour some molten aluminum into a metal mold that had a drop of water in the corner (thus, subsequent explosion).  Quite dramatic and a solid reminder of safety heh.

I've seen some folks heat up parts in a barbecue grill before breaking them, too.  Also seen others take a skill saw and just chop it up.  I'm not quite there yet, sooooo dunno what I'd do heh.

Electric furnace: I did buy Dan's electric furnace plans... and I am 50% done building it.  In fact, I was working on it the night of the burglary a couple years ago.  Just haven't been able to drag myself back to it to finish it off.


Keep the advice coming <3

[SS_N_NE]

I should find that video of a couple high school or college kids that try to pour some molten aluminum into a metal mold that had a drop of water in the corner (thus, subsequent explosion).  Quite dramatic and a solid reminder of safety heh.

I went to an aluminum extrusion plant in SD that had a good part of it's roof missing. They dropped a load of scrap into a furnace and missed a pop bottle that had been tossed in the load (tried to skip pre-heating a load of clean scrap). Don't even want to know what that experience would have been during the event.

[unfy]

Did the initial cure / test firing of the furnace today.  Was real slow and gentle with it, had it running on as low as I could get it for an hour or two before cranking it up.

I'm happy with the burner.

I'm happy with the furnace.

It was kinda of interesting to watch the furnace 'cry' from a couple of the bolt holes as it drove the water out.

After it stopped forming any condensation on a metal plate semi-covering the top vent hole, started to slowly crank the gas up. 

After turning it off, covering the vent hole with a thin sheet of metal so it can cool as slowly as possible.

I'll get some pictures posted later.

Although no melt was attempted, I will say that so far I am thoroughly impressed with propane / propane furnace.  Is the charcoal furnace worth a go for some early learning ? Yes.  Is moving to propane worth it ? So far a resounding yes.

So far, I'm not entirely convinced that the 3-3.5" hole in the lid was the correct size.  Burner didn't seem to suffer from any back pressure when the hole was 2/3-3/4 covered.  I suppose I could just slap a firebrick on top of the hole in the mean time.  And it's larger size should make adding more metal to the crucible easier... we'll see.