Casting in Brass

D

Dan Zawacki

Joined
Sep 23, 2006
Messages
366
WARNING Don't be as stupid as I am. Don't try this at home unless you KNOW what you are doing! Brass is an alloy of copper and Zinc. When heated to melting temp, and then exposed to oxygen, it will release copious amounts of Zinc Oxide fumes, which are toxic!

Now that that's out of the way, I'm in here, at the computer, waiting patiently to break open the mold on my first attempt at casting brass!

I'm working on a short sword for my son. I had a premade brass guard I had originally planned on using. However, he hole through which the tang of the previous (junk) blade passed was much wider than the tang / or blade I am working on. I tried to squeeze it down, but it broke.

So, to make a long story short, I decided to cast a new one.

Not having the proper tools and materials for this sort of project, I decided to improvise. below are some pics.

Here I am impressioning the guard (taped back together with regular scotch tape) in some Play-Doh to make an impression for pouring wax into:

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Next, I melted some wax, and poured it into the impression:

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The point is to put them together and make a wax reporduction. Unfortunately, this one broke into like a hundred peices when my youngest son took a header in the other room, and I dropped the wax on my way to rescue him!

So I plan B's the thing, and made my own original design.

used as the center cavity of a plaster of Paris mold. Once the plaster cures (24 hours) you burn the wax out, leaving an empty mold cavity.

Then, molten brass is poured in:

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Below, you can see that my little gas forge is still hot 10 minutes after I turned off the flame. I really had to cook to melt the brass. Considering I was melting brass (a bad idea for an amature like me, see warning at top) and doing it in a steel cup rather than a ceramic crucible (scale is generally an unwelcome addition to the molten semi precious metal I'm trying to cast) I tried to keep the flame very rich, while still letting it get very hot. This worked and it didn't

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It worked in that the brass didn't start to burn until after I pulled it out. When I pulled it out, the brass in the cup ignited in brilliant yellow and green flames, and the zinc oxide began to billow. The steel cup also began to scale. Fast.

I'm not sure how much scale is polluting the brass guard I just poured, but it'll be interesting to find out!
 
CRANKY!

ok, pics first:

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The messy top is no big deal. I can grind and polish until it looks all purty and stuff.

But this is another story:

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Yep, a big ol' pouring void right in the middle of the bloody thing!

Unuseable.

There's some smaller voide in the quillions too, but the big one is what really junks this piece.

Here's some more for general idea of the shape I'm going for with the new design:

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So now I need to buy some more house numbers (where I get my brass) and melt them down and try again. My wife won't let me melt this one, as it's my first attempt at casting ant it's almost recognizeable.
 
NONONONONONONONOINONHONONONONONONONO

and I repeat NO!
do NOT risk your health with brass that fumes like that

use casting bronze, or jewelers brass. there are several versions you can get from metalifferous.com I think I paid something like $12.00 per pound for my last order. When you did your burnout what temperature did you preheat your mold to? also how did you sprue it? was it an end pour or a center pour?

-Page
 
Two sprues, one on either end, just inside the little cuppy shaped thing at the ends of the quillions. Each about an eight of an inch in diameter. They both seemed to work ok. I'm not sure if you can see it, but they both have lead ins into the casiting. There' also a bit of brass left in the sprues in the mold. It was a center pour. The big ugly void is directly under where I was pouring.

I'm thinking that the mold temperature is part of the problem I am experiencing. I cheated really bad and used a common propane grill and torch to burn out the wax. I figured I was done when smoke stopped coming out, and I could blow into each sprue and get a clean sound from the main pouring cup.

Insofar as health risks, I'm actually fairly sure I'm not in any real danger. Yes, Zinc oxide is toxic, but if you look at the effects of brass fever (as it's called), you will notice two mitigating factors. 1: The effects, while unpleasant, are not known to be fatal 2: they are TEMPORARY. Unlike lead, mercury, and other heavy metal poisoning, zinc oxide poisoning is temporary. The symptoms, shakes, fever, chills, vomiting, etc, are your body's reaction to the process of expelling the zinc oxide, and when it's over it's over. No links to cancer, madness, or brain tumors years down the line, no mysterious early death from natural causes at 30, just barf your guts out, be miserable for several hours, rinse, repeat!

Also, zinc oxide fumes are quite obvious, being white / blue and thick. This is not something I'm going to be inhaling on accident (or at all if I can avoid it).


However, your advice is well timed and well taken. I will look into some jewlers brass and / or casting bronze. The prices seem reasonable, and not having to tell my wife not to go into the garage for an hour could be an advantage.
 
There are so many problems with what you did that I can only say ....
Get a book on casting from the library and read it.
Casting is fun, but requires the right materials and procedures.


PLEASE DON'T TRY THIS AGAIN UNTIL YOU HAVE READ UP ON IT......PLEASE

You know about the dangers of melting brass without the proper equipment and procedures ( but did it anyway).
One thing I will point out is that a plaster of Paris mold can explode on you ,spilling hot molten metal all around.Use casting sand or real investment. For a one-off guard that will require a lot of filing and finishing, I would make the model about 25% oversize and sand cast it. Then you file away the bad surfaces to get the final shape desired.Sand casting is the most home shop friendly way to go.You can get sand casting kits cheap (try Ebay?).
Stacy
 
Alarion said:
This may be illuminating, as it comes to zinc fumes.

http://www.anvilfire.com/iForge/tutor/safety3/index.htm

Yes, you can die of zinc fumes.
Nuff said.
:(
Click to expand...

Paw Paw Wilson was a very well known smith who died from zinc fumes. the best way to make your knives worth more is to get your name out there, not to die early in your career.
as to the casting, you may be better off with an end pour gated to the ends and middle. For bronze you want your mold to be at 1200 degrees f. for a mold the size of yours you ideally want to do 200 degrees for 2-3 hours, then 500 degrees for 2-3 hours, then 700 for 2-3 hours, then 1200 for 2-3 hours.
-Page
 
Dan, what Stacy said is true. If you are interested in sand casting instead of lost wax, I have a can of Grobet casting sand that I am unlikely to use, as I use a finer sand. If you cover the cost of the flat rate box I will send it to you.

-Page
 
Be extra careful of any moisture in the area also. One of my brother used to cast aluminum and brass and was very luck when he had a little water get to the molten brass. Instant steam explosion and molten brass flying.
 
Yes. Water can be VERY dangerous.
I once put a piece of hot iron on the anvil, where a drop of water lied, and struck it with a hammer. The bang that ensued was not unlike that of a percussion cap. The water was trapped under extreme pressure (hammer blow) and extra-hot steel, transformed in super saturated steam, reached a pressure of various hundreds of atmospheres and then was suddenly released as the hammer rebounded.
I was quite startled... :eek:

If water gets trapped in the mold, and you pour heavy, extra-hot liquid brass on it... You have the same efffect as an exploding pistol cartridge coupled with liquid brass spattering everywhere.

Molten metals are dangerous in more ways than one can imagine.
 
Sweet! thanks for the links!

This had nothing whatever to do with making anything more valuable. The guard I had intended to use on a particular project broke, and, being that I'm such a cheapskate, I decided I could make my own. I was just going to find a big honkin piece of brass to grind one out of, then it occurred to me to try and cast one.

The whole exploding mold thing is a danger that conceptually, I was at least aware of the possibility, in that I understand what gypsum is and how it behaves in relation to water and heat, but that had not actually occurred to me as an issue. Go figure.

Anyhow, I guess I have a lot of reading to do now, because, as stated, that was fun!
 
Also, a couple of things: all brass is not the same. Some brass alloys can be pretty fragile, unsuited for a handguard.
Get the right alloy.
 
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