A bar sink(usually 10" by 10") isn't useless, but it is constraining. That's what was in our kitchen for a prep sink when we bought the house. We used it for over 20 years before we remodeled. One can wash vegetables or fit a small colander for draining pasta or whatever in it, but one has to be careful to not splash.

Something like 13 to 15" wide and 18" deep would be more useful. That's big enough that you can have a pot, colander or bowl in it and still use part of the sink for other things.

Ours is about 20" by 20" D shaped.

I don't think the sink needs to match your main sink. You could do a stainless undermount and have a lot bigger choice of sizes.

My prep sink is 18x18 with a 16x16 interior and is 7" deep. For me, it is a perfect size for a prep sink. I wouldn't want to go any smaller.

If a bar sink is usually 10x10, I think that would be frustratingly small for a prep sink, but certainly better than nothing. I personally think 18" deep is way too deep. That would be a back breaker!

Also don't think you need to match the sinks. You could do something cool for the prep sink. I had a round sink in my last kitchen. There are all kinds of cool prep sinks out there.

I have a 14" round 7" deep hammered copper undermount prep sink. It doesn't match the main sink which is SS. It works fine for me for rinsing veggies and such. If I want to fill a big pot, the faucet is a pull out and coordinates with the faucet at the main sink.

I saved $$....got it on ebay for $125 vs. $500+ the plumbing store wanted.

Also, I have a "bernadette" sink...friend of ours, Bernadette, had just built their home and said one thing they regretted was putting the prep sink by the edge of the island which makes it far less useful. So we moved ours in and find it very helpful to have the counter space on both sides....

Okay, poohpup, I accidentally clicked on your kitchen pics in my email notification. My bad. It feels wicked to be so envious on Thanksgiving. ;-)

I can already see based on this sound advice that my prep needs a relook. Annie, on consideration, your friend was right. Thanks for that.

More after the holiday. Thanksgiving wishes to all.

Deep meaning front to back, not top to bottom. 18" top to bottom would be pretty odd. :) It gets confusing when talking about sinks because in the kitchen "deep" often means front to back but for a sink it can also mean top to bottom but "long" doesn't sound right either.

We have our prep sink on the island corner and like it that way. That allows people to use it from two sides of the island.

Cloud_swift, that makes so much more sense. lol I read 18" deep and thought, "Wow! She wants a utility sink for prep!" lol