Are you clearing out your toy cupboards? If your little ones are no longer playing with the old Play-Doh, then use it for trying out casting ideas before you buy expensive molding products.
I work in concrete myself, and when I want to reproduce an object in concrete, I need to make a mold of it. You can invest in a silicon or rubber material sold specifically for this purpose. They are fantastic! Often easy to use, and you get a smooth result, faithful to the original. But…also a bit pricey. Prices differ, but I paid £30 for a liter of the product that I chose.
A fun and easy way to try out your ideas beforehand or make cute tiny objects that you only want the one example of is to make imprints in Play-Doh.
Use a small box to keep the clay in place and press your object into it. Remove it carefully, and then fill the depressions with concrete. The results will most probably be a slight skew, and the surface rough and uneven. But it is instant and very cheap!
I made a necklace out of my Lego imprints! One grey and one painted with ‘Lego’ yellow!! I hung it with some platted fishnet remnants that I found on the beach.