Hi Stefano,
The surface of your resin castings are impacted by the surface of the resin mold. If a shiny template was used to make the mold, then the mold should product shiny castings. If you can, look at the surface of the mold before purchasing to see if it is shiny. If it is, you should get shiny castings. If you are unsure, ask before making purchase.
By the way, our pyramid molds will produce shiny castings. 🙂 You can find them in our store here: https://shop.resinobsession.com/products/pyramid-clear-silicone-mold