Hey,
I modelled this mold in blender, that you can print out and use it to cast a heart shape from different materials.
You can make a wax candle, or solid object that you can paint (you'll probably paint better than i do)The files are in STL and all of them are ready for printing (you have to option to print both sides instantly or separately). I also added in the raw heart if you just want to print that without casting a mold.
I printed my mold with an Ender 3V2 with PLA material on 0.2MM standard settings.
Hope you like it. Let me know what you think. cherio.