A wholesale buyer inspects a batch of signet rings and notices a faint dark line across the shank on two pieces. The factory says that is just the solder joint. It should not be visible. A correctly soldered silver joint is invisible after pickling and polishing — a visible line means the joint was overheated, the wrong solder grade was used, or the pieces were not fitted tightly. Soldering is one of the last bench steps before setting, and it is where most durability failures originate. Here are the joints we run, the solder grades we pick, and the risks buyers should check.
The joints we actually make
On production jewelry, soldering appears in four places: (1) closing a ring shank after the cast blank is formed on a mandrel; (2) attaching a stone head or basket to the shank; (3) joining chain links, jump rings, and earring posts; (4) repairing sprue stubs that grinding left uneven. Each joint needs a tight fit — a gap wider than 0.15 mm will not fill with capillary solder and will show as a line. We fit joints flush under a 10× loupe before flux is applied. The general bench tooling is listed on our equipment page.
Solder grades: easy, medium, hard
Sterling silver solder comes in three melting ranges: hard (740–770 degrees C), medium (700–730 degrees C), and easy (700 degrees C and below). The rule is to use the hardest solder that will flow for the first joint, then step down for subsequent joints — so you do not melt the previous one. On a ring with three joints (shank close, head on, post on) we use hard for the shank, medium for the head, easy for the post. We never use easy solder as the primary structural joint, because it is softer and will deform under wear. Solders are also alloy-matched: silver solder for silver, 14K gold solder for 14K gold, so the joint takes the same finish and plate. Fineness marking rules that cover soldered pieces are set by the FTC Jewelry Guides (see Sterling silver, Wikipedia).
The three risks buyers should inspect
Fire scale. Copper-bearing sterling oxidizes under the torch, leaving a dark copper-colored surface layer that requires pickling and extra polishing. If a ring comes out with a gray bloom that does not polish off, the joint was held at temperature too long. Weak joints. A joint that sweated rather than flowed will look bright but crack under stress. We flex-test every ring shank joint by hand under magnification. Overheated stones. Soldering near a set stone cracks heat-sensitive gems and can discolor moissanite. We do all soldering before setting, and we remove stones for any repair soldering — the same logic we describe in shank repair: weld vs remake.
Flux choice and fire-control
The flux you choose determines how clean the joint stays. We use a borax-based white flux for silver, which melts at around 740 degrees C and flows ahead of the solder to keep the joint oxide-free. A hand-soldered joint with too little flux oxidizes as soon as the torch leaves it; too much flux turns into a glassy crust that has to be picked out with dental tools. We also shield the surrounding metal with a heat-dispersive pad when soldering near a thin shank, so the heat does not walk up the ring and warp the opposite side. Temperature control is the single biggest factor in a clean joint: we heat the whole joint area evenly, then touch the solder to the seam only when the metal itself is hot enough to melt it, rather than melting the solder directly with the flame.
Pickling and post-solder cleaning
After soldering we dip the piece in a 10–15 percent sulfuric acid pickle at 60–70 degrees C for 30–60 seconds to dissolve fire scale and flux residue. A second boil in water removes acid. The piece then goes to the polishing line (see polishing compounds and finishing stages). Skipping the pickle leaves a dark surface that plating will not cover — we have received rejected batches where the buyer assumed rhodium would hide the solder line. It will not. Our inspection log is shared with buyers on request.
Can you solder silver with a soldering iron?
No. Jewelry uses hard (silver) solder with a torch, not soft electronics solder. Soft solder is weak, lead-bearing, and will not survive ring wear.
Will a solder joint show under rhodium plating?
Not if the joint is fitted tight, pickled, and polished flat. A visible line under plating means the joint was poorly fitted or overheated.
How do you repair a ring with stones already set?
We use laser welding (low heat, local) rather than torch soldering, and we shield heat-sensitive stones with wet tissue. See laser welding for repair and setting.
Want to inspect soldering quality before bulk orders? HOLYCOME runs hard-solder joints graded by temperature and pickle-flat. Send us a sample order — we will photograph the joint under 10× and include it in the QC pack.
Frequently Asked Questions
What ring sizes can you supply in bulk?
US sizes 5–12 including half sizes. Send a size breakdown with your order and we cast to that curve; comfort-fit inner bands reduce resize requests.
Can I order a mixed size run instead of one size?
Yes. Mixed runs are standard for wholesale: specify quantity per size and we pack and label by size at no extra labor cost.
What is the MOQ for custom ring designs?
50 pieces per design for existing molds; 100–300 pieces when a new mold or CAD model is required.
How should I price rings for retail margin?
Most partners use a 3–4x markup on FOB cost for sterling and 2.5–3x for moissanite solos, which keeps landed cost under 30% of retail.
