For our wedding we are going for a very light 'alice in wonderland' theme, which includes a 'down the rabbit hole' table where we would like guests to drop their well wishes in. The table will be covered in astro turf for a grass effect. But that actual rabbit hole will be a charity/donation bucket with a sloped lid and slot, which will be sunken into the table.
Now for my usual things like this i would cover the surface in silicone sealant, and press soil into it. Which works wonders and looks amazing. But I'm worried that if I use real soil, when people put the cards through the slot the soil will mark them as it rubs against it and we don't that.
Does anyone have any ideas on what we can use in place of soil that still looks realistic but would leave no marks on things rubbed against it?