Casting is the step that turns a wax or CAD design into real metal, and it is also the step buyers understand least. The questions below come up on almost every first call. They are answered the way a foreman would answer them on the bench, not the way a sales deck would.
Q: Can you cast directly from my existing ring?
Usually yes, but with caveats. A clean, unworn, simple ring can be used as a mold master. Inlaid stones, heavy engraving, oxidized finishes, or previously repaired sections complicate the mold because every texture is reproduced. The original ring is often destroyed or damaged in the molding process, so most buyers send a copy or authorize a mold made from a new CAD model instead. If the ring has sentimental value, photograph and measure it first.
Q: Why does the cast piece weigh more than the wax?
Because metal is denser than wax, and because investment casting adds a small amount of excess metal around the pattern that later gets filed off. A wax that weighs 1.5 grams will become a gold casting in the 12–14 gram range depending on alloy, and a silver casting in the 16–18 gram range. The exact multiplier depends on the alloy density and the spruing system, and it is something a good factory quotes before casting, not after.
Q: What causes porosity and how do you avoid it?
Porosity is tiny internal voids left by trapped gas or incomplete metal flow. It shows up as pinholes on the surface after polishing and weakens thin sections. The usual causes are: metal too cold when poured, investment not properly vented, wax not fully burned out, sprues too narrow, or contaminated alloy. Good factories control all of these as process parameters, not as guesswork. Surface porosity is usually a sign of process drift; a single pinhole is repairable, a cluster means the cast should be remade.
Q: How long does a casting run take?
From wax tree assembled to castable metal ready for cleanup: roughly 24–48 hours for a standard run, including investment coating, burnout, casting, and quenching. But that is only the furnace time. The full production step — including wax injection, treeing, divesting, and initial cutoff — usually consumes three to five working days. Rushed burnouts are a leading cause of casting failure, so a factory that promises same-day casting is usually skipping a step.
Q: Can I cast gold in a different alloy than I supplied?
Yes, but the alloy choice affects the casting temperature, the burnout schedule, and the finishing work. 14K yellow, 14K white, 18K yellow, and rose alloys all flow slightly differently and require different sprue geometry. Telling a factory the alloy at the quotation stage avoids a casting that freezes before filling a thin channel. White gold alloys with high nickel content also require an extra deoxidation step that should be scheduled before casting.
Q: Why does a cast piece need so much hand finishing?
Because investment casting is near-net-shape, not net-shape. The sprue stubs, the mold witness line, slight surface texture from the investment, and minor flash at joint lines all have to be removed by hand. A clean casting still expects three to six minutes of bench work before it even reaches the polisher. Buyers who wonder why casting is cheap but finished pieces are not should remember that finishing labor is where the cost lives.
Q: Can a casting be remelted and reused?
Sprue, buttons, and defective castings can be returned to alloy, but they have to be refined — new grain added, oxidation skimmed, karat re-tested — before reuse in production. Reusing alloy without refining builds up impurities that show up as discoloration or brittleness in later runs. Ask a supplier whether their returned alloy goes through an in-house refining step or is sent out, because that difference shows up in consistency over large orders.
Q: Why does my cast piece come out thicker than the wax?
Investment ceramic is porous and expands slightly in the burnout furnace, and the sprue geometry adds metal where it is not wanted. A competent caster accounts for this by shrinking the CAD or wax model on screen before printing, so the final piece hits target dimensions. If every piece a supplier sends comes out 10% heavier and thicker than spec, they are not accounting for expansion — and the difference in metal cost comes out of your margin. This is also why weight-based pricing on custom pieces should always quote a target finished weight, not a wax weight.
For the full picture, read our lost-wax casting overview. The pattern across all of these answers is the same: casting is a controlled process, and factories that treat it that way are the ones buyers can reorder from a year later without surprises.
Rhodium plating, which gives white gold jewellery its bright finish, is covered in the Wikipedia article on rhodium.
Related reading: Lost-Wax Casting vs 3D Printed Wax for Jewelry: What Actually Changes , Lost Wax Casting Jewelry Process Explained, Jewelry Soldering: How We Join Metal at the Bench.
Frequently Asked Questions
How do I verify a factory before placing a bulk order?
Request a production video, business license, export records and a paid sample run. A factory that accepts a 50-piece test order is usually a real manufacturer.
What payment terms do you offer?
30% T/T deposit with the balance against the bill of lading. This protects both sides on first orders and can move to net terms after a track record.
What is your normal reject rate?
3–5% under 10x loupe inspection for cast and set pieces. Defective units are replaced free in the next shipment.
Where is the factory located?
Wuzhou, Guangxi, China—the core lab-grown and moissanite manufacturing cluster. Shipments go via Guangzhou or Shenzhen ports.
