How can I make a fake engagement ring for a proposal decoy?

Most fake engagement rings look exactly like what they are, and for a proposal decoy that is mostly the point. You want a ring that reads as a diamond from across a restaurant table, not something that falls apart in your pocket on the way there.

I've made a few of these over the years. Last March a client named Daniel came in because his girlfriend had found the real ring while hunting for her passport. The real one went back to his parents' house and we built him a size 6.5 sterling silver solitaire with a 9x7mm cubic zirconia. Total bill was $78. The snag: she loved the decoy so much she wore it for two weeks before he admitted the real stone existed.

Start with cubic zirconia, not moissanite

A high-quality cubic zirconia is the right decoy stone. It's cheap, it's bright, and in a simple solitaire it photographs well. Moissanite is double refractive and throws rainbow light that doesn't look like diamond if anyone peers closely. For a decoy that may be handled, examined, and carried around for a week, CZ is the better choice because most people won't question it.

Get one with a 9x7mm or 8x6mm oval, or a 6.5mm round. That's the size range of a typical one to two carat diamond center, which is what most people expect. Don't buy a 4-carat "diamond" unless your partner already knows your budget is enormous. It will look like glass.

Two settings that work

The easiest option is a finished sterling silver or 10k gold ring from a supplier that already has a CZ set. You will pay somewhere between $40 and $120. Sterling is fine for a few weeks of wear, but it will tarnish if she leaves it damp. 10k gold is about $60 more and safer if the decoy might sit on a finger for a month.

If you want something that becomes useful later, have a jeweler set a CZ in a plain 14k or 18k gold band. That costs around $250 to $400, but the mount is real. When the real diamond shows up, you can pop the CZ out and set the genuine stone in the same ring. I've done this twice for clients who wanted a surprise proposal now and a diamond picked together later. It works.

Size it quietly

Steal a ring she already wears on the correct finger. Bring it to a jeweler and have the decoy sized to the same diameter. If you can't get a ring out of the house, trace the inside of a ring onto a piece of paper with a sharp pencil. Most jewelers can get within a quarter size from that.

Somewhere around 60% of the engagement rings I make start with a stone the client already owns, so I know the sizing dance well: men guess, and they guess wrong about 80% of the time.

What I would not do

Avoid gold-plated brass with a foil-back stone. The plating rubs off and the finger turns green, and the foil backs cloud from hand lotion. If the decoy only has to survive a dinner, it's fine, but I've seen too many men hand over a $20 ring that leaves a green line before dessert. That's a tell.

Also don't set a CZ in platinum as a decoy. The labor cost is wasted on a stone worth less than a nice sandwich. If you're spending platinum money, you should be spending it on the real ring.

If the decoy is for travel, keep the real ring at home and photograph it first. Use the photos for insurance, not for showing off at the airport bar. A travel decoy is the one time I'll tell you to buy a cheap silver ring and not think twice.

If the decoy is for the proposal itself, tell her it's a stand-in.