I was wondering if you can advise me on the best material for a medal. I believe bronze is normally used for medals, but I would like to know what are the advantages and disadvantages in using brass:
Is it easy to cast in brass?
Does brass have any symbolic meaning attached to it?
Thank you so much.
Roberta
Both are primarily copper, the differences are the alloying materials used to make them. Also, there are many, many different types of both, depending on what the copper was alloyed with, how they are to be used, properties that are wanted in the final product. Most sculpture (bronze) is cast in herculoy or everdur. Herculoy is more liquid thus easier to pour and fill the mold but any welding shows up as the zinc in the alloy mix burns out and the filler metal changes color and shows up in the final product and it is not as corrosion resistant as Everdur. Everdur is a bit harder to pour (easier “freezing so does not fill as well” but welds absolutely do not show up in the final product and it is stronger and often used for marine fittings. There is Ancient bronze (copper and usually tin) that was often used in earlier centuries for casting (they did not weld then but used different methods of connecting). Some patinate differently/harder than others, and on and on.
You can get the same sort of variations in brasses. The list for both alloy types, bronze and brass in very long………….
I cast bronze sculpture so I have Everdur but I also did some custom casting in white bronze (I did NOT like it al all and would not do more of it). Copper is the base/primary metal in these alloys but copper by itself is difficult to cast as well as having other short comings in other areas, and on and on and on………………
Hope this helps a bit.
JD
Adding to John’s excellent comment, the main consideration for a simple, cast object like a medal is the alloy’s reaction to different patina formulae. You should investigate various patinas and then choose an alloy that gives you the look you want. The Colouring, Bronzing and Patination of Metals is an excellent reference and formulary.
Hughes and Rowe, The Colouring, Bronzing and Patination of Metals, The Crafts Council, London, 1982
In the Olympics, Bronze, Silver and Gold medals are awarded. All these metals have alloys that work best for casting, machining, die-striking, etc. If you want to cast a bronze metal, the silicon bronze alloys like Everdur have a lot to recommend them; they cast very cleanly, with little damage from gas inclusion and are easy to weld, since compatible rods are available. But “ancient bronze”, an alloy of copper and tin, also casts well and has a lot of history going for it.
The same cannot be said for brass, a more modern alloy of copper and zinc. When you melt it, it immediately starts emitting a dense toxic white smoke. A heavy layer of flux will slow but not stop this reaction. Zinc has a very strong tendency to combine with oxygen and form zinc oxide (the stuff lifeguards traditionally slather on around their eyes to retard sunburn). The process of forming this material also can cause gas bubbles to form inside the cooling metal mass of your medal. It might show itself right away, or it could wait until you remove a little metal from the surface to reveal a big black hole.
Perhaps that’s why nobody awards their winners a Brass Medal. The difference in the price of the metal pales into insignificance when you figure in the failure rate. You can save money using cheaper metals if you’re producing something in large volumes and you can spend some time tweaking the process until it works reliably. But if you’re just trying to make one - or even a few - of these things, use bronze, not brass. It sounds more expensive and you’ll get paid more for using it.
There have been some great replies to this question and my initial reply. One more to at least consider is some of the “gold” replacement casting materials available from many of the jewelry supply companies. I have never cast with them but my, now deceased wife did to make “sample rings” for some of her wholesale/retail folks as well as for her store (when she had one - before me being in her life). Just another thing that might be useful to the initial question or for others who do not know about this sort of thing.
John
Thank you so much for all your advice. Much appreciated.
Roberta