It's best to use very small amounts (2 pixels at best). It's easiest to use a METL rod (1 pixel) at a distance of 1 pixel like in this diagram: http://cl.ly/1gY2 This is a simple AND gate. the middle conductor is METL, once that has a current, it will heat the NTCT very quickly, despite its distance, allowing the right conductor to transfer electric current to the left. For more examples, see: http://powder.hardwired.org.uk/View.html?ID=2754