I bought a melting furnace to do bronze and brass castings with and need to rigidize and coat the ceramic insulation before I get stared. I have some colloidal silica, specifically west systems 406, to make rigidizer. Is this appropriate for the task at hand? If so, at what ratio should I mix it with water? PS. If anyone knows where I could get brass for casting in small quantities that would be great as well.

 

Thank you

 

After re-reading your question during my final edit I realized what you want to do so I deleted my how to advice. I WILL NOT participate in a young person's almost guaranteed health threatening hazardous activities.

One last word of wisdom. Unless you have a vacuum melter and casting station you can NOT safely melt brass. The zinc in the alloy WILL oxidize and YOU will BREATH it. This is a B A D N E S S thing.

You just do not have the knowledge, equipment nor experience to cast brass. Just asking how indicates you don't know any better. I have a friend who is a professional bronze caster and he will NOT allow brass in his shop. PERIOD

I'm not dissing you, I want you to practice metal craft for decades to come and show us pictures of it all. To that end I tend to come across strongly with people about to make a seriously dangerous mistake. IGNORE what you see on the internet, anyone claiming to cast brass is either lying outright or poisoning  themselves.

Frosty The Lucky.

 

Well that is good to know. What about bronze though? That was my main imputes, so sending brass down the road isn't a problem.

Modern bronze alloys usually contain some zinc but not nearly as much. Good PPE is a must, especially breathing gear.

Frosty The Lucky.

20 hours ago, Frosty said:

The zinc in the alloy WILL oxidize and YOU will BREATH it. This is a B A D N E S S thing.

Assuming that he plans to remelt used brass parts, I would worry more about the lead content than the zinc content 

Maybe you can get your bronze casting friend to jump into the conversation, Frosty.

Yeah, I forgot about the lead content to make the melt flow better in the mold but thinking about it, how about the cadmium to make it stay shinier? 

Pat would be a great addition to the IFI gang but he doesn't use a computer except to place orders and such. His wife is who might reply but she wasn't a metal person, her thing was pottery, painting and wood carving. 

What I do know is he goes through any salvaged bronze very carefully to make sure no brass sneaks in. Anymore he won't use salvaged bronze unless he's certain of it's origin, lots of bronze in the last couple decades is almost indistinguishable from brass. He buys silicon bronze with a guaranteed analysis by the pallet. He does remelt his own but nothing from outside.

There're waiting lists for his classes AND he's the go to guy for bronze monuments in Alaska. 

Frosty The Lucky.

Is this appropriate for the task at hand? If so, at what ratio should I mix it with water? PS. If anyone knows where I could get brass for casting in small quantities that...

The more you mix into water the thicker the solution gets; if it is thin enough to be used in a spritzer bottle, it is fine. If you mix it too thin, the food coloring that you put into the water, will alert you. This is one of those tasks hat you can do sloppy, but you can't get wrong.

Start off with aluminum castings; it is a lot less serious, when you make mistakes.

When you must get serious, employ silicon bronze. You can remelt it over and over, with reasonable safety.

Use the correct safety gear, with the correct fume filters. Work outside; especially while you are learning what to do.

I hope you also purchased a stainless steel, sand filled, container to set the furnace on. When, a crucible breaks, you want a safe container for its contents to run into. 

Aluminum is a good place to start casting but casting aluminum has a pour temperature around 1,100f this is slightly hotter than the liquidus but you want it as close as reasonable. The thing is 1lb. of molten aluminum spilled on a concrete floor will blow molten aluminum 30-40' in every direction.

The safest metal to cast is that in a casting class. Many colleges have casting extension courses where a person can learn to do it right. Regardless casting molten metal is inherently dangerous and mistakes are not just painful they are excruciating for weeks or months and disfiguring for life. Heck, really serious burns can kill you with the shock.

Casting is not a trivial pursuit. Take a class and pay close attention.

Frosty The Lucky.

I’ll see if there are any classes in my area and go from there. I don’t intend on melting scrap to much for the sake of consistency and knowing what alloy I’d be working with. PPE is top of my list, I may meet different respirator filters though. Thanks for the info, don’t hesitate if anyone has any more suggestions. 

23 hours ago, CaribouForge said:

Thanks for the info, don’t hesitate if anyone has any more suggestions.

Since you asked:

(1) Frosty was right as far as he took it, but collage classes are just one avenue. There is quite likely to be at least one hobby casting group in your area. Go on line, and look up home casting sites, to inquire about such a local group; it is likely to consist mainly of guys who retired out of various trades, and took up hobby casting for something to do; they will have learned quite a bit about safety over the years, and learned how to keep safe in their hobby as well.

(2) The level of danger in casting has to do with three things: Melt size; pour temperature; and particular fumes given off by various metal oxides. This is the particular danger of using metal scraps. When it comes to brass in general, and imported brass parts in particular, you will be clueless to what oxides you are dealing with.

  This is why casting aluminum is the path most people take, to get into metal casting. There are metals with lower pour temperatures, but all of them have much more serious fumes, including zinc. Aluminum scrap, from beer cans to wheelium, produce little in the way of fumes. How come? Well, aluminum alloys contain mostly...aluminum, and its oxides do not even melt, let alone boil at the flame temperatures that air-fuel burners reach. In fact, you must add some zinc into the charge, to get the melting process started. Then, those oxidized particles  are chemically converted, to liquefy, rather than be directly melted.

(3) Aluminum and most other liquefied metals (with the exception of some white metals) will cause  concrete to explode upon contact; this will then fling liquid metal all over your shop, and all over yourself.

  Crucibles can eventually crack, spilling their contents into your furnace, and then right out of the emergency spill hole at its bottom. This is why hobby furnaces are set in steel  tubes with three or four inches of dry sand; it will contain the overflow, keeping it off that concrete floor.

  But what about the pour area. You could have an accident, and spill a little bit, or a lot, between the furnace and the molds. The pour area can be contained in a square made of two by fours, filled with sand, ending the need for a tub. The furnace, molds, and the shop space in between, all rest on a layer of sand; it can be swept up into a container between pours, and the wooden square leaned against a convenient wall.

(4) The next steps are all about larger, more efficient, and way safer equipment. I would suggest that you hunt up a PDF of Gas Burners for Forges, Furnaces, & Kilns to see how to build your next burner and casting furnace. There is probably still a couple of pirate site giving away free copies of the book; I seem to remember eight sites at on point 

  Or you can buy a used copy through Amazon.com, learn what you need to know, and then resell it through Amazon.com; dozens of people have. Thousands more won't let go of their copy (just a bunch of hoarders, I say).

All metal casting is dangerous. A little bit of moisture even in a lead melt can be catastrophic doesn't matter the temperature.

I would not consider aluminum to be the best or safest metal to cast. My opinion obviously doesn't mean anything here, but have any of you cast aluminum before? 

Pure aluminum is hard to pour and can only make basic shapes like a cylinder. Plan on machining the heck out of it. 

Have you heard of die cast. Almost all aluminum parts are die cast.

FYI die cast aluminum contains zinc just like brass. 

As for lead you probably can't get it hot enough for vaporization, but the dust left behind is the real danger.

So if we are only talking about temperature then yes aluminum  is safer.

In my opinion bronze is the safest metal to make and pour. Other than the temperature. 

Don't melt any type of scrap. They all have their own dangers.

Make true bronze. 90% copper and 10% tin. 

Don't use pewter buy pure tin and alloy it with scrap copper like water pipes and motor windings. Windings do have a coating on them thou, so burn that off before you add them to your crucible. If you're worried about safety.

There is no safer alloy than that. Cast anything you want. Intricate molds are no problem. 

I would not recommend any novice to cast anything on their own.

 

Florida Man,

 I don't completely agree with all of your views, nor do I disagree with them. Your insights come from doing the work, and things you have seen first hand. I totally respect that.

I spent a quarter century involved with hobby casting groups, both online and in person. And the bottom line I saw with newbies, was their desire to  cut costs by cutting corners. I'm confident that my crack about "beer cans and wheelium" did not slip by you. I don't think that the lower pour temperatures makes aluminum safer than brass; it just seems so to novices. It is the lack of fumes from the scrap pile that those novices want to use, which reduces risks; anyway, that is how it looks to me. If you can show me how my deduces went wild, I will only thank you for it.

Speaking of insight, your advice on mixing copper scrap and tin, to make real bronze, instead of all the junk they lable 'bronze' these days, was sharp; it was so obvious I can hardly believe that I never thought of it...

Please, say on. I know there is more good stuff where that came from 

Mikey

I beg to differ Florida Man, your opinion means quite a bit here, especially in your professional field. I know I've rubbed you the wrong way and regretted it then and now. Unfortunately I get going and part of my method is to take the position of devil's advocate, I learn more from disagreement than agreement. I can take it too far, especially with folks I think of as friends I can argue with without fighting. If that makes sense.

I was glad to see you posting again and read every one.

Thank you for your above post and expertise alloys have changed a great deal since I did much casting. I started casting lead sinkers with Dad in aluminum molds, open and closed. Yes, I've cast aluminum, lots of aluminum all green sand from 2nd semester jr. high (middle school) through high school, 2 semesters a year. We cast some scrap if it was cast aluminum, preferable thin section castings like motorcycle cylinders and heads. 

Aluminum was a much simpler alloy in the 1960s though pure aluminum wasn't available then or as far as I know now except as a specialty. 

Aluminum cans are crappy for casting as it's an extrusion alloy that almost liquifies under pressures and has self lubricating properties so it will flow between the male and female dies. Not considering the anodizing and dies the walls are so thin the % of aluminum oxide per good al. is to high to be worth the trouble of collecting and melting it. Recyclers are prepared to recover al cans folk are better off collecting the deposit and buying ingots for casting. 

I was pleasantly surprised when I checked, to see pure tin is available online, about $28-$30/  lb. plus shipping, etc. I only checked on seller so I'm sure prices vary. 

My question is, were I to want to make bronze what method should I follow? The liquidus of "pure" copper and tin are, about 1,500f different. I can't think of good happening dropping an ingot of tin in a crucible of molten copper. Maybe introduce the copper into molten tin and let eutectics work?

Enough of my speculation. What say you, please?

Frosty The Lucky.

Florida man is no professional or expert anything as the name implies. You folks have much more knowledge than I will ever gain. I'm a one trick pony. 

We are all guilty of getting carried away. Me included.

I'm not saying anyone is wrong or right. Just observations. 

I'm using scrap yard logic when talking about aluminum. My pure aluminum comment refers to extruded aluminum. By definition it can't be reasonable cast that is why it extruded under immense heat and pressure.

As for cast aluminum some yards have a different category for die cast aluminum mine does not.

Take a torch to cast aluminum/diecast and watch all the different colored sparks that come off. Include greenish yellow for zinc. As to the science of cast aluminum and its properties I will leave to those smarter than I. 

As for making bronze it simpler than brass. When making brass you have to first melt copper then add zinc and account for the lose of zinc because of vaporization of the zinc. If you are trying to make an exact percentage it is rather hard because you have to add more zinc than you need to end up with the proper ratio.

For bronze you just weigh out the two metals in the exact amounts you need and put both metals in the crucible and bring to casting temp. Tin in the bottom copper on top.

Tin melts around 350f and copper around 2000f sounds like a world apart. But tin doesn't vaporize till like 4700f. So there is no lose of the tin. What you start with is what you end up with.

Have you guys seen the video of the guy who stick his head in the alligators mouth. He performed shows for the tourist. He did this trick thousands of times until one day the alligator clamped down on his head. He got complacent from doing it so many times. He probably didn't even consider it dangerous after awhile.

He forget the main rule. If anything touches the alligators tongue it would clamp down. 

Guess what his down fall was. A drop of sweat. He forgot to wipe the sweat from his brow on that fateful day. 

That is what I equate metal casting to. Right or wrong all it takes is a drop of sweat in your crucible to end your casting days.

Uh HUH. We actually have a lot in common, be afraid, very afraid. Nobody with the curiosity to look up things that interest them is less than an expert at where to learn specifics if they're needed. 

I read enough about a topic to get a "handle" on it. With a handle I know what to look up if I need the info even if it's just a category it's a head start. The other plus being I don't actually have memory files filled with maybe someday information, just a table of contents, a decent library and the internet. 

It's largely Mother's fault, she rarely told me the meaning of a word, she taught me how to look things up instead. I could tell if she thought I was being lazy when her answer was, "What did the dictionary, encyclopedia, etc. say?" Danged if I didn't turnout to be somebody who loves etymology

I stopped saying much about what's in an alloy when I discovered, "Mild Steel" was a special order. A-36 is NOT mild steel. The steel industry had changed from analysis specs to performance specs. For some things it makes logical sense. For others it's just randomization slipped into the supply stream.

Anymore I get pretty vague about what's in an alloy and spend more time here explaining why you can not trust found steel to behave like a 100yro blacksmithing book says it will.

Then again if it's important, XRF metal identification tools are darned accurate and reasonably priced depending on how accurate or portable a person needs. It' sort of an accuracy vs. portability scale. REALLY accurate XRF is something you don't want t be around or have good shielding when it's operating. Hand helds are pretty accurate but not close enough for much. 

Oh yeah Mr. alligator feed was a classic example of being hoist by your own petard. There was another clown who we used to quote or exemplify as a gene pool self chlorinator. I believe he finally killed himself with one of his home made explosives. 

There was or is an old adage I've used here but has been around longer than I remember. "If you going to the well sooner or later you will drop the dipper." Do anything long enough and eventually it will get away from you. I have dents in my head from one of my experiences with that fact of life. I'd felled literally thousands of trees and that one got me good.

Dad used to say, (until I was sick to death of hearing it) "Familiarity breeds contempt."

Wouldn't have mattered if I'd taken it to heart and observed it with religious zeal. Sooner or later. . . Stupid tree!

There was a high school science teacher who took exception to the metal shop instructor's warning about how inherently dangerous metal casting is. Mr. H. the heavy metal shop teacher held multiple PHDs in metal sciences. To disprove him, the science teacher() teacher cast mercury in a super chilled mold, no fooling liquid nitrogen chilled! Pieces of his PLASTER OF PARIS  mold were stuck to 2 walls and the acoustic tile ceiling, The mercury ran off all 4 sides of the table FAST. That was okay though, mercury wasn't nearly as dangerous in those days. 'Thermal shock, what's that something to eat?'

Fortunately the mold's "USD" (UnScheduled Dis-assembly) wasn't very forceful AND it wasn't in a LNI bath.

Human beings can be fun to watch if they don't do others or themselves a serious mischief.

Frosty The Lucky.