Usually you want a sentence to have no more than 2 commas. Otherwise the sentence gets too long. (Exception being lists) If you speak the sentence out loud, note where you naturally want to pause for breath. This is the use of commas. For long pauses it would be a full stop.
There is more complexity and rules than this for the use of commas, but as getting a basic grasp, you should see improvement in your punctuation.
Second, she explained that although it took ten minutes for wood to catch fire, there are sticky substances in on ships named pitch, which catch fire in seconds.
In order to reduce the commas I would get rid of Second and start with "She then explained that".