Heat that purifies...

Metals like Iron and Gold are found in the earth but with many impurities attached to them. To make these metals useful and look good we got to put them through a hot furnace. As the heat rises, the impurities vanish and we get a very useful, shiny, beautiful piece of metal...NOT a burnt one.
In life, God uses hot furnaces to purify us too! Paul clearly says that we aren't to be surprised to see trials in our life; a Christian life is filled with trials. When these trials come they bring us closer to God - God promises in Isaiah 43 that when we (not 'if' we) walk through the furnace, we WILL NOT be burnt! The heat cleanses the impurities and helps us shine brighter, for Him above.
In chemical reactions, the rate of reaction is faster when the temperature is higher due to faster movement of particles. Likewise, God rises in temperature to purify us quicker and trigger a movement towards holiness.
So next time you walk into a furnace, REMEMBER...you will come out purer, shine brighter and that it will NOT burn you!