title_body: How to judge time between cracks when roasting
upvoted_answer: Distinguishing between end of first crack and the start of second crack can be very tricky. A lot has to do with the variety of beans being roasted and your heat application.
  
  What I think happened to you was that you lost control of your heat. At first crack your beans become exothermic (give off heat) and you didn't reduce your heat. What happened then is that you had too much heat at raced through the "development" time in your roast profile. 
  To correct this you should reduce your heat at the start of first crack and develop the flavor by how much/long  you let the beans go for before taking them off the heat.
  This is a critical time for your roast because your are developing the flavor in your roast by time and roast level. How you apply heat changes from variety to variety and darkness. 
  Take the time to read up on roasting theory.
  
  Here is a good basic guide: A basic roast profile guide for home coffee roasters.
  
  Good luck