Differences between Casting and Fabrication of Metals
Both fabrication (making jewelry out of mill goods like wire and sheet) and casting are wonderful techniques for jewelry... but there are differences in the end result.
Almost all jewelry you buy at a shop, especially mass-produced, is cast. The advantages are many: once one has created a good master, and a good mold from that master, one can cast an almost infinite number of that design!
Plus, there are things one can do in wax (or sometimes other materials) that would be difficult or impossible to do in metal itself; that's another great reason for casting.
However, casting has its drawbacks, too. Cast pieces are invariably more brittle than fabricated ones. Metal, like most things, expands as it heats up and contracts as it cools off. That means that the hot metal that fills the mold (which is usually a type of plaster in lost-wax casting, the most common way to cast) develops tiny holes in it as it cools into a solid from its molten state, rather like a sponge. This is unavoidable, although good casting techniques do minimize it. These tiny bubbles, though, do mean that the end result is a stiff foam rather than solid all the way through- and that makes it somewhat more likely to crack instead of bend when put under stress.
Again, good casting techniques minimize this and allow a fair amount of manipulation even of a cast piece, but it's a vulnerability of the process.
(For PMC/Art Clay fans- these are like casting but more so. The organic binder that allows them to act like clay burns off, leaving holes in the fired metals, making it more brittle than castings. This is why PMC rings, for example, are usually overbuilt when compared to cast or fabricated ones; that's necessary to correct for the increased brittleness.)
We metalsmiths usually use "fabrication" to cover making items individually from mill goods (purchased sheet, wire, tubing, and the like). Mill goods are denser than castings, because they have achieved their basic shape by mechanical means such as rolling in rolling mills, and the drawing out of wire. While mill goods start with ingots- which are essentially cast- the manipulation of them into the shapes needed compresses the metal and reduces the sponginess of castings.
Therefore, a piece of metal exactly the same size from a casting and a mill good will be heavier and denser in the mill good.
This can be an advantage in jewelry, because in general, the denser it is, the better it wears (given similar hardness), and the less likely it is to crack under stress.
Also, there are few shortcuts in fabrication; each piece must be made individually, and cannot be mass-produced like castings can be.
Almost all my jewelry is individually fabricated from mill goods. For rings and bracelets in particular, I am just not convinced that cast work holds up as well. For these and other things... well, I'm a metals artisan because I like working with metals! It's important to me to be hands-on with every piece that I make, and my commission work is always made individually for the person who requests it.
I do have some cast pieces for sale, but when it's cast, I make that clear. And I am careful to only cast items for which the increased brittleness will not be a problem. I have myself made all the masters for my cast pieces, and do the finishing myself. (Since I am not an expert caster, I generally get an expert caster to do the casting itself, to insure the highest quality.)
For wedding and commitment rings in particular, I value being able to make each one individually, for that particular person, and keeping them informed of the process (including sending photos of their work in progress). So many things in modern life are mass-produced; I like being able to make people the exact wedding rings they want- by hand- and am always honored when I am asked to do so. I also really love that I can make these rings sturdy, suitable for hard wear for many years of committed life! I've made replacement bands for people whose wedding rings have worn out, and while I'm honored that they asked me to do that- it should not ever be necessary with my rings!