"Can't you just tap it up?" "What about stretching it?" I hear this from customers, usually after I've told them what it is going to cost to size their ring the right way. I'm not sure where they heard it from, but this is not good for the ring. 'Stretching' or 'tapping' just spreads the metal, making it thinner. It will also pull from the weakest point, so if it's not a solid band it will stretch first at those thinner areas. If there are stones set, it can loosen them too as it stretches the metal around them. The only time you should stretch a ring is if it is a solid band that has never had anything done to it, and even then you should only stretch it a maximum of one size.
So if we're not 'stretching' or 'tapping', how do we size your ring?
To size a ring you must first make sure it is clean. Any lotion or skin oils on the ring when heat is applied can burn into the metal. This is also true of stones, assuming it is one that can be left in while you work. Any stones that can't, are removed next. Lightly pass the torch over the shank to see if the ring has been previously sized so you can plan your cut(s). The shank is then cut with a jewelers hand saw. If we are sizing it up, we will be adding metal. If we are sizing it down, we will cut some of the metal out. When sizing down, we always cut from the thinnest portion of the shank (that spot on the back that gets the most wear). When sizing up, you are opening the ring slightly and placing the extra metal in the space. When you size it down you are closing it in. Once that is done, solder and polish your joins. Reset any stones and make sure any that weren't taken out are still tight. Polish the whole piece.
The metal that the ring is made of is a modifying factor.
Sterling is a pain. It conducts heat evenly, so the entire piece will be the same temperature as the area you are soldering. Unless it's a diamond, any stones have to come out before it can be worked on. Unfortunately, these stones have often been glued in as an added security against them falling out. They must be soaked in a special solvent that only dissolves glues, which can take a while (in one memorable case, it took two weeks). Previous solder joins on the piece may flow while you are working, which you will have to go back and redo. The bigger part of your expense with a silver repair is that it is very labor-intense.
Gold doesn't conduct or hold the heat like silver does, making it the easiest to work on. The bigger part of your expense with gold repairs is the cost of the metal.
Platinum has a melting temperature of 3,215 degrees Fahrenheit. Never work on this metal without proper eye protection or you will burn your retinas. (never watch me working on it either) It also has terrible metal memory- which means that when you bend it, it wants to go back to it's previous shape. This adds to the time it takes to reshape the shank for sizing. It has the double whammy of being difficult to work AND expensive. Because we don't add hardening agents to platinum like we do with gold, when you buy platinum it is all platinum. Expect to spend (on average) three times what the same repair costs in gold.