I dont know what painting technique that you are planning but for a solid color I would use concrete porch paint. They also make it in a stain. You may be able to use acrylic paints and then seal it with some kind of polycoat. But one of the smarter ladies will have to help out on that one. Also try over on the mosaic forum. They do a lot of work decorating concrete step stones.

I would like to hear more about what you want to paint on the step stone. Words? or just color?

Susie

I love stepping stones but I'm extremely picky about the the ones I like. So, I'd be interested to hear what you want to paint on them and how your project turns out.
I'd think that the concrete would soak up any type of acrylic paint? So, you'd have to do many coats or have an aged look or seal the concrete with something before you started painting.
Vickie

When I painted some of my concrete black I used some left over latex paint and added some of that stuff that people use to make paint dry slower so it can be worked for special faux effects. (I had bought a gallon way back but didnt use it all in my fauxphase) Forget what its called. My theory was that would give more liquid to soak in but not change the color. It has lasted very well. My friend just spray paints hers with cheap spray paint, but it sometimes wears off. My has lasted well thru 3 winters so far.
kathy

I also used some black oil based stain that I found in the cellar, really old, and that has not lasted as well as the paint plus the extender. Boy it was hard to get off my arms tho. I was speckled for a week.
kathy