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Author Topic: Inquiries on Brass Casting  (Read 1450 times)
Merry Maid of Yarnover
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« on: January 26, 2013, 09:52:18 pm »

Hello all, I'm new to the forum, and was wondering if I could pick your brain a project of mine. I want to make a brass version of a toy wand I've had since childhood, and was wondering the best way to go about it. Is there a method of casting that produces a hollow inside? It is my ultimate goal to be able to light the finished piece up, as I've seen in some cane and raygun projects. I've searched through the archives of this forum, and gleaned a lot of information, but I feel it's best to ask directly. If it helps, I'm sure I could scrounge up an image of the part I'm wanting to cast.


Alternatively, would a resin cast be more suited to my purposes? I know there are ways to make the resin appear metal-like. It would certainly be lighter...

Your knowledge and guidance is much appreciated!
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Narsil
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« Reply #1 on: January 26, 2013, 10:19:54 pm »


Drop me a PM
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« Reply #2 on: January 26, 2013, 10:25:58 pm »

Sadly new members can't use the PM functionality to cut down on spam. If you spend a few hours on the forum as a registered member you'll automagically level up to the next rank (Deck Hand I think) and you'll be able to send PMs then!
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DreamHazard
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« Reply #3 on: January 26, 2013, 10:38:52 pm »

What's the issue with discussion in public? Surely it's better to share your information with the rest of the forum?
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Narsil
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« Reply #4 on: January 26, 2013, 11:05:53 pm »


I have no problem discussing it in public Smiley It will just be quite a long post and advice depends a lot on the specifics of the project.

The general outline is as follows:

Brass can be cast successfully but it does have some limitations. One particular problem is that if you get the wrong alloy or overheat it you will release zinc fumes which are highly toxic. With that in mind Brass is not the ideal starting point for learning metal casting. In fact metal casting in general is something which needs to be approached with caution.

In general it is possible to make hollow castings, depending on what the pattern is. There does need to be some opening in the piece somewhere though, you can't cast something with a completely enclosed void, not in one piece anyway.

When you say you want to light the piece up do you mean you want it to glow from the inside or just have internal space to fit wiring for external lights ?

If you want the whole thing to glow then brass or any other metal isn't an option as any metal more than a few atoms thick is opaque to visible light.

Casting in resin would certainly be a reasonably option and most likely the the most practical solution if you want to do it yourself.

There are also a huge number of possible differnt approaches, depending on exactly what you;re trying to make and what resources you have available.





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DreamHazard
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« Reply #5 on: January 26, 2013, 11:34:47 pm »

I have no problem discussing it in public Smiley It will just be quite a long post and advice depends a lot on the specifics of the project.

That's cool because that's the whole point of the topic Cheesy

Sorry if I seemed a little short, I'm used to making forums where private discussion is massively frowned upon, as it detracts from the community spirit.


Personally I'd go with resin, as Narsil points out it's the most practical option.

It's possible to create a "complete" hollow cast using resin if you employ a technique known as "Slush casting", which is where you pour a small amount of thin(ish) resin inside your mould and then rotate the mould to promote even coverage all the way around the mould.
This technique takes practise but it's fairly simple in principle.
The only thing you really have to worry about is wearing a mask if you're using certain resins, and doubly so when sanding, which you'll have to do because there'll be seams from the mould.
A dremel (or similar) is excellent for taking off the initial seam, then grading sandpaper to smooth out the surface should leave a beautiful finish.
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Merry Maid of Yarnover
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« Reply #6 on: January 27, 2013, 12:26:48 am »

Thanks guys, all this feedback is much appreciated. If I went with the brass casting, the hole would not be an issue, as there would be a hole at the top for a big ol' piece of cut glass that will (hopefully) be lit up from underneath, and one at the bottom to meet the shaft. It is my ardent desire to make an updated steamy Sailor Moon wand. I made a regular costume a year or two ago, and that's all well and good, but I feel that it would really translate well into steampunk if executed properly. Here's a pic of the wand, the version I've had since 1996 is on the furthermost left:
http://25.media.tumblr.com/tumblr_ln9em4xia71qivj1oo1_500.jpg

It's looking like I'm probably going to go the resin route, eh? How shiny is the resin that's made to look like metal. Is it comparable to brass?
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DreamHazard
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« Reply #7 on: January 27, 2013, 12:42:38 am »

It's looking like I'm probably going to go the resin route, eh? How shiny is the resin that's made to look like metal. Is it comparable to brass?

It depends on the materials you use, you're looking at painting the thing once it's finished, so you'll need to sand, a lot, but you can have a pretty realistic finish when you're done.
You'll need to sand, prime, sand, paint, sand, seal, sand, buff and polish. It's time consuming but once it's done you'll have a beautiful piece.
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Narsil
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« Reply #8 on: January 27, 2013, 12:58:13 am »

That looks like it should be castable without too much trouble the gold bow just below the crescent looks like it's undercut but you should get away with that with a two part flexible mould. The could be either a latex or silicone skin mould with a plaster counter-mould or a silicone block mould. A silicone block mould is probably the easiest route but the material is a bit more expensive.

You can simulate metals by mixing metal powder with the resin. Two things to watch out for are the metal powder tends to thicken the resin quite a bit so it doesn't always pour that well. What you can do it paint the filled resin onto the inside of the mould and then assemble it before it cures, being careful not to get any excess resin between the mating surfaces to the mould. The other thing is that it takes quite a bit of mixing so it's best to thoroughly mix the powder with the resin before you add any catalyst, allowing it to sit for a while to allow any bubbles to settle out. If you need a lot for a large mould or matching parts it's best to mix the powder and resin in one go and add catalyst to small quantities as required as matching separate batches exactly can be  tricky.

The other option is to use a fairly sticky mould release agent, like vaseline and then dust the inside of the mould with the metal powder and pour the mould as normal (adding a pigment to the resin may help to bring out the metal colour). Thsi is fairly straightforward to do but can be a bit hit and miss on more complex castings and will give a relatively thin layer of metal effect on teh surface so not ideal if you are likely to need to do a lot of clean-up on the casting.

The dusting method should give a decent metal effect straight out of the mould. If you mix the metal powder with the resin you will need to cut back te hsurface a bit with wet and dry paper or similar and then buff to the required finish.

The main part of this piece was made using resin mixed with aluminium powder : http://www.chrisjohnssculpture.co.uk/photo_5814772.html
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« Reply #9 on: January 27, 2013, 06:39:07 am »

Ms. Yarnover has neglected to mention whether she has any prior experience with metal-casting, which is a major factor in choosing a method to replicate cast metal. I don't cast myself, but I've read enough to support Narsil's opinion that brass is not a metal for beginners.

If you want to look into casting, one good starting point (in my non-caster's opinion) is BackyardMetalcasting.com. Mr. Oliver's focus is on aluminum, but that seems to be the place to start. He also has a great many links to a great many other sites.

Finally, since I've found it rather difficult to find, here's a link to a page on K-Bond synthetic-oil-bonded casting sand as developed at Kent State University.
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Merry Maid of Yarnover
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I just want to make it all...


« Reply #10 on: January 27, 2013, 08:26:30 am »

von Corax: I have done metal casting projects before, but with lower melting temp metals, and in a professional forge environment. I certainly will have my work cut out for me if I decide to go the brass route, but I'm well aware of the safety risks, and plan on getting the help of friends who are far more familiar with the process than I.

Narsil: the resin dusting technique actually sounds like my best bet. I'm extremely tempted to go down that path. As for the bow, I was thinking of taking artistic liberties with it and making it a pair of wings instead. There's a later version of it that features wings on the shaft of the wand.

Thank you gents so much for all your knowledgeable responses. I'll be sure to post pics when I get the ball rolling on this. For now, more research Smiley
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DreamHazard
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« Reply #11 on: January 27, 2013, 08:30:09 am »

Why not make a thread to hold your research and work in progress? It'd be a nice way to document your progress and make some friends within the community Smiley
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« Reply #12 on: January 28, 2013, 12:07:00 am »

My first thought on seeing the image you provided was  'Metallic spray paint and a Banana'.

My brain works that way sometimes.

My next thought was that the piece might be easier to reproduce as a fabrication from tube and beaten sheet metal.

The handle would be fairly simple to flair out at the ends over a conical stake and two crescent  shaped plates could be dished and soldered/brazed/glued together.

A bit of searching though the jewellery stores should provide the right sorts of shape for the connecting sections and a few upholstery pins could be added for the domed fasteners.

Me?
I'd go with the Banana.

Yes, and what Mr Dreamhazard said.
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« Reply #13 on: January 28, 2013, 03:02:17 am »

If you go the resin-casting route, you may find that applying a metal leaf or thin foil gives you a much shinier, more metallic surface than powders or paints can. Non-gold alloys, like "Dutch Leaf" are not too expensive. On the other hand, on parts that will take a lot of handling, leaf, even with a clear coat, may have some durability issues. It may also be worth spending a bit of research time to see if some of the metallic fittings can be matched from brass parts available in stores and on line. There are huge numbers of finials, switch-covers, and cable pass-throughs out there, and finding some which would suit your build could save a lot of headache in the long run.
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« Reply #14 on: January 28, 2013, 03:19:55 am »

Being a steampunk maker, I see a copper pipe handle flared out to mate up to an upcycled brass crescent moon (possibly a candle stick found in a thrift store) held together via a threaded rod or solid bar peened over. The decorative bits would be riveted or bolted on...
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« Reply #15 on: January 28, 2013, 08:08:49 pm »

I also think the fabrication route may be the way to go. Could be easier than casting in the long run.
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Narsil
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« Reply #16 on: January 28, 2013, 08:32:11 pm »

I must say that if it was me I would definitely cast it rather than fabricate it and I  tend to favour fabrication.
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Professor J. Cogsworthy
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« Reply #17 on: January 29, 2013, 02:31:17 am »

A cast version is going to be a lot heavier than a fabricated one...... if that matters.
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Merry Maid of Yarnover
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I just want to make it all...


« Reply #18 on: January 30, 2013, 06:09:30 am »

My first thought on seeing the image you provided was  'Metallic spray paint and a Banana'.



Haha, if I didn't so dislike the scent of rotting fruit, I'd go for it!
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Merry Maid of Yarnover
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I just want to make it all...


« Reply #19 on: January 30, 2013, 06:16:31 am »

I also think the fabrication route may be the way to go. Could be easier than casting in the long run.

The only thing I'm really interested in casting is the moon at the top, the rest I think I can pretty easily approximate. Instead of the jewel part on the shaft, I think I'm going to try to dummy up some sort of light up gauge since I'm lighting it anyway. Now that I've been reading all these pages online about resin casting, I really want to go for it. I've got my brother's interest piqued as well, haha.

The metal alloy plan sounds like an excellent idea, thanks Mr. Boltneck!
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