Sanity check before I break things..

[ttabbal]

Hello all, I'm new here but have been reading the fine forum for a while. I am currently looking to set up for casting. I'm looking to start slow, so no I'm not planning to melt steel as the first project etc.. Aluminum to start, possibly as high as copper/brass/bronze later, but I'm not in a hurry. 

I started building a basic furnace a while back but I didn't like the way it was going and decided to read up more and consider the form. It started as one of those little garbage cans, but I think I was trying to stuff too much into it. So I decided to set it aside and go with a larger unit. I picked up a 12kg forge/furnace kit from Vevor. I know commercial links are not allowed, so I won't post one. It is a stainless dual burner setup that you can lay down to use as a forge. I know it's not ideal, the idea is to have a base to start from. It comes with what they claim is 1.2 inches of ceramic wool insulation, maybe in the lid, but the main unit is probably more like 1 inch. I'm tossing around adding another 1 inch blanket in there, but it and the refractory would likely make the crucible not fit. Not the end of the world, I could use a smaller crucible and save the one it came with for the future. Is it worth the bother to make the insulation thicker? 

It came with "refractory cement". Not sure what kind, but from the videos I've seen of people using it, I don't think it's going to get used right now. I have 15lbs Kastolite-30. And Matrikote for the IR layer. Of course fumed silica for the rigidizer. 

The plan is to rigidze the blanket then fire it. Perhaps adding more wool here. After cooling butter the inside and apply kastolite. After setting, which sounds like it needs humidity and time, dry and fire again heating slowly to make sure water is gone. Then another cycle for the Matrikote. I might need to look at building a form for the kastolite, but it sounds like pressing it on the wool by hand is enough. 

I'll also be making some lifting and pouring tongs. The kit included some, but they grip the side of the crucible, which sounds like a good way to break it. 

[George N. M.]

Welcome aboard from 7500' in SE Wyoming.  Glad to have you.

If you add your general location to your profile we will have an idea of where you cast you shadow on this hunk of rock.  This is a world wide forum and we don't know if you are in Lapland, Tasmania, or Kansas.

In my experience crucibles are pretty tough and I can't imagine crushing one with crudible tongs.

I'm sure that you have read the threads about safety and PPE for casting, even for metals with lower melting temperatures.

My only recommendation is to rehearse the movements of picking up the crucible from the furnace/forge and carrrying it to the mold and pouring the metal into the mold cold/empty before going live (hot).  That builds muscle memory of the movements needed and reduces the possibility of a mistake or booble when things are dangerous.

"By hammer and hand all arts do stand."

[ttabbal]

Thanks

I updated my location. 

Good idea on rehearsing movements for moving the crucible while cold and empty. I can see that being helpful and it's something I've done when learning other skills that could cause harm. I'll certainly be doing that, and re-reading safety info before melting anything. I'm trying to take it slow and learn. In that direction, I think I'll make sure I start with small quantities of material. Less molten material at a time is probably safer overall. 

Edited October 5, 2023 by Mod30
Remove @name tag

[George N. M.]

Well, by western US standards we are practically next door neighbors, only 350 miles apart. ;-)

GNM

[Frosty]

Crucible tongs don't have the leverage and the bit end are shaped to distribute force around the crucible, they'd bend before breaking a crucible provided it isn't a home made one. 

Pouring tongs or ring don't apply anything but lifting forces to the crucible.

YES rehearse the actions and get the idea molten aluminum is somehow les hazardous than molten iron! Spill 1/4 cup of molten al on a concrete floor and if you can't rake it over a wide area QUICKLY it WILL "pop the concrete." That means raising the temperature of the concrete above the temp required to break the hydration bonds between the calcites and water in the concrete causing a steam EXPLOSION. The chips of HOT concrete that fly from the floor, called "spalls, the process called spalling," will generally fly up to about 30' and blow molten aluminum along with it. Yea, that is molten droplets and blobs of aluminum AIRBORNE.

And nothing will MAKE YOU drop the crucible like molten metal popping the concrete after a little runs of the mold and then you have a couple few lbs. to be sprayed around your casting area. 

So, what is your casting area like? What are your spill precautions? Are the flammables removed back farther than 30'? How many fire extinguishers do you have and where are they hung? How good is your 1st aid kit? When was your last 1st. aide class? Ever performed serious 1st. aide on yourself? 

How about your spotter? You ARE going to have a spotter, especially for your first pour. AREN'T YOU? How good is hi/her training, been there for rehearsals?

You can mitigate most of the hazards by pouring over a pour box. This is a shallow-ish open top box filled a couple few inches with DRY coarse sand or fine gravel, Kitty litter isn't a bad choice. The sand box will disperse any spilled melt into sparts small enough to cool very quickly and keep it out of the air. 

Casting metal is NEVER a trivial pursuit, it is always dangerous. Bringing the pain and possibly scars to your grave is only the beginning, your homeowners insurance isn't gong to cover it and will cancel you if they find out about it accident or not. That really sucks if you burn the house down.

Be careful, there is nothing that can't bite you, sometimes no matter how well prepared you are.

Frosty The Lucky.

[ttabbal]

Thanks for the info Frosty,

The tongs the vendor included are basically large pliers. I could see them being used for forging to hold the work, maybe loading material into a hot crucible, but I've seen a number of people concerned about crucible damage with tools like that. What I would call crucible tongs as a newbie would have some shape to grip large areas of the crucible to distribute the forces, ideally just gravity. It sounds like what you described with "Pouring tongs or ring don't apply anything but lifting forces to the crucible." is what I want, but what I have would put compression forces on the rim of the crucible to hold it while lifting if I used them. 

I do understand about concrete, having managed to cause spalling with welding. I do appreciate the extra warning though. Safety has to be at the front of the mind when working with things that can hurt you. 

Area... That is a good point. 30' is a fairly large area, more than I expected to be concerned with as a primary work area. I was initially planning to set up a work area with firebrick lining for the "hot" areas. I also like the pour box idea you mentioned. I planned to work outdoors with flammable material removed. Mostly concrete areas, but with coverings for safety/spills at least where the work will be. I'm still evolving the ideas for this area of concern. I plan to buy a couple more extinguishers to dedicate to the area. Probably another first aid kit as well. I have one nearby, but having it right there would be better. I can't say I've had a recent class, but I am familiar with how to use it and have worked on myself. I leave real work on people to the professionals, but I can generally get things good enough to get to a pro. 

Spotter, yes. Experienced, no. Not sure how to find someone that is. The Utah group here is pretty dead. I've been learning online and from books like those from Gingery and other older material. And youtube, but I take things there with a grain of salt. 

I'm reminding myself daily that I know nothing. I don't intend to melt anything for weeks, at best. Initially it will be open molds for ingots and similar. Taking time to learn and fix up the furnace. I'm only planning to light it to do the dry-out of the lining materials and crucible. Since we're in the insulation sub-forum, do you have any thoughts on my insulation plan? 

Edited October 7, 2023 by Mod30
Remove @name tag

[George N. M.]

BTW, pewter (lead free is best) is a metal with a comparatively low melting point which is not a bad starting metal.  If it wasn't for the toxicity issue I would suggest lead but pewter is a pretty good analog.

GNM

[ttabbal]

I might try pewter first, thanks. I've done a little work with lead, but nothing I would consider very useful from an experience perspective. Custom shaped counter weights for a project. Which makes "dump lead in an altoids tin" sound way more interesting than it is. And, obviously, lead has other problems.

Like I said, no big rush to get melting things. I'll get there when I get there. 

[Frosty]

Check out one of the casting forums and do NOT try making what you THINK are the right kind of tongs or other tools. Lift tongs have curved bits thought not necessarily form fitting, that close up smaller then the fat part of the crucible. They only lift straight up.

You aren't going to find a lot about casting on blacksmith forums and what I've seen on knife fora is pretty basic and often pretty iffy. An experienced caster can get away with a degree of iffyness but it's a REALLY BAD idea for a beginner.

Things like a sand box pouring area aren't ideas, they are long established casting equipment. If nothing else an open topped metal or metal lined wooden box. NO, do NOT think the ground is a safe place, ground is seldom dry unless you live in a desert. The chips spalled on concrete are nothing compared to the molten metal they splash into the air. 

Something I forgot to mention safety wise. NO SYNTHETIC clothes! Natural fabrics or leather only. Well, if you have an aluminized fire suit okay. Nomex is only good for temporary flame contact or as insulation under an aluminized fire suit. Fire fighter's Bunker gear is good but bulky.

Synthetics melt on contact with temps about 300f and above above though some melt as low as 250f. The molten plastic then sticks to your hide and deep fries you. This is a B A D N E S S THING.

You and the spotter practice together and develop an emergency plan. In jr. and senior, high school metal shop classes there were one sometimes two safety spotters with pushers. Sort of metal bladed floor squeegee thingies to move the melted al around till it cooled to prevent concrete popping. The class rooms didn't have a metal pour box or sand/gravel but only the instructors poured and the safety guys had to prove they were good for the job. 

The only time we had a serious incident was in high school occupational Heavy Metal shop when one of the "joker" students deliberately damaged a number of the molds. Call him mook lifted the flasks and kicked the bottom knocking large holes in the sand so the molten al would run out and onto the floor. I doubt mook thought about popping the floor with often fairly large volumes of molten al right on top. Large being around 4 cups +/-.

mook's intent was to screw up other guy's castings because he couldn't get even the simplest to work himself. The instructor didn't waste time pouring, usually emptied the first crucible in under a minute, so IIRC 3 flasks were blown a couple few feet into the air, the green sand molds were blown apart and molten al was blown up and against the hot area hood. The entire area, probably 30' square was covered by a steel hood to collect smoke and contain the occasional explosion. 

The instructor bellowed OUT and we ran for it. Clearing the edges of the hood was the main goal but getting farther away was best. Lots of us got splattered. I got hit on the back (Yes, I was running) and the al ran right down my spine on a sheen of sweat. All I felt was a hot streak and it escaped without getting hung up on my belt or pants. A couple of the guys got 1st degree burns but we got off lucky. Well, escaping that cleanly even with class training and occasional drills, was still lucky.

We may have suspected who pulled the stunt but it wasn't until mook started bragging about it and how he did it were any of us sure. He got himself 86ed from any shop class in Cal for a stunt in wood shop a couple weeks later. He lifted the stop on a table saw because he couldn't get a 2" x 6" (maybe, this was the mid/late 60s after all) board to feed. And when the board touched the blade it was ripped out of his hands and launched across the shop and speared the wall above the desk work area. 

Mooky boy had already been forbidden from the paint booth area, he enjoyed sniffing paint, thinners, etc. too much to allow hin anywhere near. Same in auto shop and he'd been 86ed from crafts shops, they worked almost exclusively with solvents, paints, resins, etc. A glue sniffer's heaven.

Sorry for the side track but I've been up close and personal with quantities of spilled al on concrete, steam explosions are amazingly powerful things. 30' was all the farther those went because of the hood. I'd really rather you didn't experience even a small one.

As a kid I used to cast lead fishing weights in the kitchen. Of course casting lead wasn't hazardous in the 60s, almost nothing was.

Frosty The Lucky.

[ttabbal]

No worries about the safety discussion. I don't mind reading more about safety. I appreciate it as so many of the places I see people discuss casting tend to almost ignore it. And videos show things that even as a beginner I know are dangerous. 

I know this forum is more about forging. Just seemed like you had some casters too. And I am interested in forging as well. So I might just keep that here and look for casting elsewhere. Seems like insulation and refractory applies to both, at least for the beginning levels. But if that's not done around here, I don't mind following the rules. 

[Frosty]

Oh there are plenty of casters aboard it's just not a regular subject. I don't know why one of them hasn't jumped in here I'm dredging up jr. and high school memories. I cringe when I hear someone say they "learned" to do an inherently dangerous craft online. The only thing a person needs to be a Youtube expert is a camera and internet connection. The majority are just bad info but some are outright dangerous. The now deceased "king of randumb," was a prime example of dangerously stupid how to videos. 

There are how to videos on Iforge and to be included here they've been vetted by our folk and we're not easy on anybody, especially where dangerous crafts are concerned.

Anyway, your question now. Insulation isn't as necessary in a melter but it's good to have. Rigidizing and covering with a hard refractory is really important for safety and really lengthens the useful life of the machine. 

What's more important is getting the spacing between the crucible and melter wall right. YOU want just enough space for the flame to flow around and up without inhibiting the burner performance. This is one reason lift tongs are shaped the way they are, the bits are curved for fit AND to pass through the minimum space to get to the narrow part of the crucible.

The "plinth" is a small block of fire brick on the bottom of the melter the crucible sits on. It's smaller than the crucible bottom so there is the max flame contact to the crucible and still support it firmly. 

The burner is aligned just above the floor of the melter tangentially to the wall and directed slightly downwards. The idea is to keep as much of the flame inside the melter and between it and the crucible as possible. This transfers the max energy to the crucible and melt. This is the reason the exhaust port is a small hole in the melter's lid. 

Insulation isn't as important as getting the size, shape and flame flow correct but it IS a factor.

Oh, I almost forgot there needs to be a drain hole in the bottom of the melter so if (when) a crucible breaks the melt can drain and not cement everything to the inside of the melter. Talk about a major PITA chipping, prying and generally cussing it out of the melter! In some cases it's bad enough the caster just scraps the melter and builds a new one.

Frosty The Lucky.