Homebrew PCBs

So I took a run at it.  I printed my artwork to magazine pages, then placed
on my copper and ironed away.  The first attempt failed pretty hard

. 5 minutes with the iron and maybe 40% of it was missing.  I cleaned the
board with acetone, printed again and this time went to 10 minutes.
Better.. but still missing bits.  

 

Wondering where to look for problems here?  Paper?  Iron not hot enough?
How do you know?

 

Also.. is there a limit to how many times you can attempt ironing on a PCB?

 

Brad