What adjustments do I need to make when preparing toffee at a high altitude?

"I live at 5400 feet altitude; what adjustments do I need to make when making toffee?"

I asked Institute of Culinary Education baking and pastry arts chef-instructor Jeff Yoskowitz, who told me he ran into the problem himself when visiting his wife's family in Quito, Ecuador, which is 9200 feet above sea level. He follows the guidelines below as a general rule, but finds he often has to tweak the amount of fat and liquid in the recipes by trial and error.

At sea level:

223-234° thread

234-240° softball

244-248° firm ball

250-266° hard ball

270-290° soft crack

295-310° hard crack

315-350° caramel

For every 500 feet over sea level, drop the temperature by 1 degree. At 5000 feet, for example:

213-224° thread

224-230° softball

234-238° firm ball

240-256° hard ball

260-280° soft crack

285-300° hard crack

305-340° caramel

For more tips on making candy, see The 7 Deadly Sins of Candy Making.

Recipe: Salted Chocolate-Pecan Toffee