Touch the loaf and if it feels sticky then it's too soon, wait until it feels smooth and has a dry touch to it and you can pick up the whole loaf in your hands without it denting in. That's about the only way I can explain it, it all comes down to practice and the experience, as you go along you will know when it's ready. For me it's make one day, put it in the frig, unmould the following morning let sit one day and night, then maybe cut the next or wait another day. So that's 3 to 4 days. Just don't get too impatient.