savagenights

Pewter melt/cast question by a new hobbyist

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Firstly, I apologize if this is the wrong area, short time before I head into work and wanted to make sure I got this asked before a day of stress makes me forget about it.

Basically, the question I have is that, knowing pewter can be cast into plaster of paris (provided it's baked enough to drive off moisture), is it also possible to directly melt the pewter into a mold using something that can heat the whole assembly to the right temperature? Ideally using a 3 part mold, where the top is a "universal" section that has a recessed pit of some kind to hold enough pewter for the casting, along with a funnel/sprue? to direct the melting pewter into the main mold, which would be a 2 part mold that the pouring section would sit on. The whole assembly would be tied together in a metal flask of some kind, probably aluminum since it's easier for me get my hands on right now, load it up with just enough pewter, chuck the whole thing into an oven, or similar thing, turn up the heat, and then wait.

 

Would this work? or are there other problems that would have to be resolved first?

(FWIW, I'm near Cincy OH. I'll get that part sorted after work)

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Don't reinvent the wheel here.  Get yourself a good casting book and a lot of your questions will be answered--it's not that you are terribly wrong, but many of the glitches with your plan have already been worked out over the years and reading up might help you spot those.  Books on lost wax casting will overlap a lot and have some good advice about handling molds so may also be worth the read.

"Pewter" means a lot of things...from the old lead based kill-ya stuff to the more modern replacements.  On top of that, there are different melting points to alloys available--even down to melting in hot water so more info is needed there.

As to "plaster"..yea, it's been used but the true casting plaster is not expensive and is worth the slight extra cost.  It doesn't break down easily under heat, is very fine for reproducing details, is compatible with additives to get rid of surface bubbles when making the mold etc.  Typically a mold won't fill well without some outside help like centrifugal force (for small stuff)...or being very well designed with proper venting.  

And..how much is "enough"?  Are you casting tiny "tin" soldiers or a massive tankard?  Multiples or one-off?  Most molds these days for low temperature alloys are actually done in things like silicones so they remain flexible and can be re-used easily.  It's fairly easy stuff to work with, especially of there are fine details to reproduce on multiple parts..

Sorry if it sounds snotty but I think you need to do a little more basic research on casting in general...and then many of your questions might resolve themselves.  

 

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Can you take a jewelry making class at a local community college that includes a casting section?

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14 hours ago, Kozzy said:

Don't reinvent the wheel here.

Dont worry, I've been in your shoes regarding other subjects before, so I do understand the feeling. As for the question I posed, lost wax casting was actually what prompted me to think about it and go "since you melt/burn the wax out of the mold, can you go backwards and directly melt the pewter into the mold?" I do know, and understand, that there's more than just "mold, melt, pour, enjoy" to this stuff, so more reading and research definitely will be done. Though half the time it feels like my brain's just a cat stuck in a room with a laser pointer aimed at a disco ball. So many things trying to get my attention so I often pick something to deal with before I forget about it. 

Regarding the type of pewter I meant, at the moment I've been waffling between the R92 or R98 alloy pewters offered by Rotometals. Both are lead-free with melt points around 470F and a pour temp about 100 degrees above that. They also offer a Britannia pewter as well, but it's melt point is roughly the pour temp of the other two pewters they have.

As far as mold media, plaster came to mind first as something that might be more affordable to use when first starting out, as it's likely to be more forgiving to mistakes, whether because of the material itself, or by the fact that it's not as expensive as silicone molds. Currently planned ideas, for keychain medallions (2" dia, 1/4-1/2" thick), would use roughly 4 ounces each pour, and wouldnt involve much in the way of fine details (like filigrees for example) so much as having simple patterns either engraved or embossed, whichever may involve less work in the end. I'm also thinking of making, or having made, wood positives made to allow easy reproduction of molds if necessary.

11 hours ago, ThomasPowers said:

Can you take a jewelry making class at a local community college that includes a casting section?

It's something I can look into, but for reasons I wont into here, is probably unlikely to happen any time soon.

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Of course the obvious problem with that method is the question of where does the dross go ?

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Simple molds, why not use petrobond?   I once did a run of flat skull plaques in silver for a belt using tuna fish cans for the cope and drag, (and a hose clamp to hold them together). I would ram the bottom (drag) full and then dust it with parting compound and  impress the pattern and ram the upper one (cope) on top of the pattern/base.  I added the sprue and risers to the pattern so so we were ready to pour by the time you have the plaster mixed to start. (I attended a casting class held out of hours at a local university's Fine Arts department that used petrobond for casting brass back around 1983.)

Note that I have transferred finger prints accidentally using clean fresh petrobond.

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You're actually adding a level of complexity while trying to simplify the process.

Frosty The Lucky.

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I have less experience than Mr. Powers, but I would recommend the petrobond too.  You might consider picking up the Dave Gingery books. Some fun stuff on simple casting.  I've found pewter, mostly Brittania metal at flea markets and thrift shops.  Don't fear, I don't melt down any true valuables, it's mostly the folded, spindled and mutilated that find their way into my crucible. Three part seems a bit much to me, I'd stick with the tried and true two part cope and drag. Have fun, and be careful, even low temp casting can still have nasty issues.

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actually, to me it sounds like you have all the knowledge you need to give it a go.  All you need now is a bit of hands on to answer your questions.  

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