It's gotta be THIN, around 5mm or less. Frankly the thinner the better, it gives it a sort of luxurious melt in your mouth consistency (room temp too). For soy sauce I use Tsuru Bishio 4 year aged soy sauce. It's like 40$ a bottle but it's so strong and rich that I tend to use very little at a time (one bottle lasts me like 6 months).