you do not have to use vermiculite in such a way as to cause direct contact with the mycelium. i personaly use a coaster to place the birthed cake on and use vermiculite soaked in a 90% distilled water and 10% hydrogen peroxide mix (the hydrogen peroxide helps keep the vermiculite from getting funky smelling) in a bowl in a terrarium with a tight fitting seal and air it and mist it 2 to 3 times a day with the same water mix used above. have had fantastic results with this method and no contact with the vermiculite has ever occurred. good luck