Hi Pam. Those are some very helpful cam details. Thanks!
Wanted to throw in my 1 cent to the discussion. Here are some quick notes of what happens with cam-type bloomy rind cheeses and what can go wrong:
1) This is post mold-forming, when the whey has drained and you have cute cheese wheels. They're either salted, or the curds have already been salted. You either spray on the camemberti or it has been added to the milk. Now, the surface must dry out. This is done by using a normal 55-65 temp, but at lower humidity, around 70-80%. This is crucial. At this point, the mold needs to start growing on the rind. If you've added geo, it will build the foundation for the p. candidum, and your salt levels can't be too high, or the geo will not grow. p. candidum starts when pH is around 5.6-5.8.
2) So, the yeast or mold geo has neutralized the surface. It also has started to eat the cheese rind and has sent little feet into the cheese to get a foothold. This is the point that makes or breaks the cheese with regards to slip skin. Too high a temp (more than 55F) and the geo will liquify a tiny outer layer, making it too wet for the p. candidum to send its feet into the rind and grab a foothold. Too little salt (less than 3-4%), and same thing. The pH here on the rind doesn't matter as much at first. Also, too moist of a rind, and the geo will make it even worse.
3) Assuming your temp was great, you used the proper ratio of geo to p. candidum (1 to 5, IIRC), salt was ok, and you resalted after a few days to retard geo growth, the cheese is blooming. Now it's been 4-7 days at 50-55F. This is the next stage things can go wrong, but by this time it's usually too late. If the humidity is too high (>95), p. candidum will be slow. If the pH was too low or too high, as Pam posted, the rate of proteolysis will be off. What happens with p. candidum is that it actually eats the lactic acid. The pH of the cheese influences both how much lactic acid is there and the rate that the lactic acid moves from the inside of the cheese to the outside. That rate of movement in turn influences liquification as the mold releases enzymes that cause proteolysis and liquification. Too high of a pH, and inside will be too soggy. Too low and outside will be too soggy.
4) Let's say now that your pH was great, moisture was fine, you left the cheese for a day to dry out the rind before transferring it to a more humid room/box, you salted correctly, didn't use too much geo, there's air circulation all around the cheese, and you're now about 2 weeks into it and there's no slip skin. You're almost there. The two things that can go wrong now are temp fluctuations or too high of a humidity. Lower is better here in terms of temp. It will take longer to age the cheese, but 50F is just fine. Humidity should be in the lower 90s.
If you do that, you should get a great cheese. The top two causes of slip skin, like Pam said, is too much moisture early on/not enough salt, so that the p. candidum can't get its feet in and bond to the rind, or later on, the pH/temp is off and liquification doesn't happen properly. Well, or there's not enough air circulation around the cheese and it physically gets wet.