In geological usage, "sand" is a term that relates to the size range of the particles, from 1/16mm to 2mm. Blasting sand would generally be an angular silica sand. If you use silica sand (think quartz beach sand) in the dome you remove the possibility of moisture absorbed by the individual grains, unlike calcareous (limestone, as an example) or mixed sand which can hold moisture in pore space in the individual grains. Of course, there is still surface adhesion of moisture, which is why you want to keep the sand as dry as possible, but, generally speaking, there is less surface area in a clean quartz sand than in a like-sized and shaped calcareous sand. By using a pure, washed silica sand it seems you have half the battle won. I doubt that "black beauty" would be any better in this application.

If you keep your engine inside, open lid on the dome to let the moisture out over night.

Ted Rita
General Manager
Hesston Steam Museum
www.hesston.org