i used slate, if u peep my albums u can see what i made. TBH, i just washed the slate and let it dry just regular water and then i siliconed it together with dap 100% rubber silicone sealent, a darker blue tube and let the silicone dry for about 36 hours i think, usually good to wait 2 days or so. no need to wash it again before puttingit in, i would have a nightmare if i had to rewash mine since its so large