Several years ago, in pre-blog life, I used some as molds for concrete stepping stones. They weren’t super-successful. For example, my favorite shape was a curved fish, but in popping it out of the mold, it broke. I also probably pulled the stones out earlier than I should have- the longer concrete cures, the harder it is, so popping them out early meant they were fragile.
We had a half bucket of concrete mix left, though, so last week while the boy was at STEM summer school, Kate and I got messy.
I had read on the internet (gardenweb has great information about concrete garden ornaments of all kinds) that adding latex paint as part of the liquid to concrete can extend the working time, and strengthen the finished product. I poured in some of the “Amethyst Frost” paint left from the last time we painted Kate’s room into the mix. It totally doesn’t change the color- the concrete is still grey.
Kate was much more persnickety about greasing her molds with petroleum jelly, so the ones she worked on came out much better than mine. We also got some marble gems at the dollar store, and she was in charge of placement. I would have gone crazy and carpeted the stones with marbles, but she was very reserved.
With the curved fish and a sea horse mold, I attempted to reinforce the concrete with mesh from an onion bag. The delicate parts broke anyway, so I glued them with 9001 high strength adhesive. Once they are in place, there won’t be a lot of stress on them, so they should be okay.
I waited several days to pop them out of the molds, kept them covered with plastic, and misted them with water every time I remembered to, all on advice from the garden web forum people.
All in all, I am very pleased with the results- we have some good-looking stepping stone/border edging pieces. You should recognize that you cannot use the molds for food again- the vaseline helps the concrete to release, but there are still bits of gravel stuck to the inside. The molds are about a dollar each at thrift stores (rest assured, Mom, that I didn’t use the copper mold you gave me, with the flower design- it is still hanging on the wall in the kitchen). I have an idea for what I’m going to use the copper molds for now…watch this space.