Any handcrafted product made will have noticeable differences between two items made by the same artist. Addressing this issue with copper sinks is a system of grading that helps sort sinks into quality categories. Three primary categories determine copper sink quality: copper purity, copper gauge, and construction technique.
Copper sinks should be 99% pure copper with 1% zinc for strength. Copper can be recycled and melted down repeatedly and reworked into new products. In fact, 80% of all the copper ever mined is still in use today.
Copper purity is important for several reasons. In the Middle East, India and China lead is used in the alloy because lead is inexpensive. The problem is lead is poisonous. No safe threshold for lead exposure has been discovered—that is, there is no known amount of lead that is too small to cause the body harm. Needless to say, you’ll want to avoid a copper sink with lead added to the copper.
Copper Gauge (Thickness)
Copper is a soft metal which is why a sink’s longevity is based upon its gauge or thickness. Kitchen sinks take a lot of abuse and for the sink to last many lifetimes it should be a thick gauge. The copper gauge runs low to high, with low being the thickest. You can find bath sinks made with 20 gauge (the thinnest available) to 16 gauge, but a good kitchen and farmhouse sink will range from 18 gauge to 14 gauge.
A thicker gauge sink will be more expensive but there is good reason to pay a little extra. Lighter gauge copper will always create a noticeable metallic sound when the faucet is turned on and water drums on the sink surface. Sometimes lower quality sinks are insulated with foam blocks in an effort to help reduce the “tinny” metallic sound. Plus, light gauge copper dents more easily, which is a consideration for kitchen sinks that will experience heavy wear.
Hand-hammered products won’t ever be perfectly shaped, but they should not be “out of square” or “out of round”, so you’ll want to avoid any sink that is noticeably misshapen. Misshapen sinks should be sold as seconds if they are sold at all.
You’ll want to inspect the sink drain opening, which should measure the correct size to meet code for your application. Copper sinks can be custom made with the drain where you require, but check that the sink bottom gently slopes toward the drain.