Crystalline intelligence is the accumulation of facts, figures, knowledge, etc over time. This increases with age, and you have to watch out to make sure you don't let this acumulation of things that you know stop you from learning new things.
If you do, then you end up becoming a bit of a fuddy duddy. The worst example of this problem has to be the guy who discovered the data for the oxygen theory of combustion. He published his results, and when the theory was publicised, refused to believe it. In the end, towards his death, only a few people still considered the previous phlogiston theory of combustion as having any credibility at all.
Henry ford disliked this tendancy so much, thatif he heard any of his engineers saying that something couldn't be done, he would fire them, and hire someone who didn't know it couldn't be done. they usually managed to do it.
This contrasts sharply with Fluid Intelligence.