An issue with any hot metal is how long is it going to resenate heat after the burning of the rest of the structure. The Scarring of the playa is actually the bisquing of the clay material the playa is made up of. An average fire burns from 1000F to 1500F unless it is being aided by somthing like wind. You could get metling to occur depending on other factors when you burn you work with the brass in it. Other fluxes could be present or material that helps burn the other parts to higer temperatures. For example: When i fire wood kilns, I can reach temps up to 2500F with wood alone if i fire in a specific manner with certain woods. If i get a good breeze the day i am firing hitting the fire ports then it can boost the fuel burn rate and jump the temperature quite fast. If you do have a good layer of sand below you burning work as suggested above then this can help "sponge" up any molten materials. I use sand in the kilns to act in this way when i am using very high flux based clay materials that can melt all over the place it the temp spikes for some reason.
From out of a dream I rode to beyond the Horizon. Got Adventure? The Zen Gear One Meteior Crater surrounded by a lot of roos, emus, Yowies, drop bears and one major flood in the driest desert on Earth... There still was a bottle of red with dinner.