Wednesday, 14 May 2014

Temperature conversions

The internet is dominated by North America which continues to use the traditional imperial measurements, although the rest of the world uses the metric system with its length, volume and weight units inter-related. Until North America catches up with the rest of the world, we will continue to need to convert temperatures from one system to another.

The conversion factors relate to the reference points of water's freezing and boiling points.
The Fahrenheit system has these at 32 and 212 – 180 degrees apart.
The Celsius system has these at 0 and 100 – 100 degrees apart.
This means the conversion rate is 9/5 to go from C to F or 5/9 to go from F to C.

Instead of dealing with the fractions, it is easiest to multiply or divide by 0.555 which is accurate enough for kiln forming purposes. Multiply the Fahrenheit by 0.555 to get the Celsius equivalent. From Celsius divide by 0.555. So a rate of advance of 200F/hr becomes 111C/hr( 20*0.555) and a rate of 80C/hr becomes 144F/hr (80/0.555). This works fine for calculating the rate of advance.

It does not work for temperatures. The complicating factor is the water freezing point in the Fahrenheit system which is 32F. To calculate the Fahrenheit temperature in Celsius, you first have to subtract 32 from the Fahrenheit temperature. So to convert 212F to C, you first have to subtract 32, giving 180 which is converted by multiplying 180 by 0.555 which results in 99.9 which is close enough to 100C.

To convert from C to F you divide the C temperature by 0.555 and add 32 to the result, e.g., 515C becomes 960F (515/0.555=927.9+32=959.9)

Alternatively you can bookmark one of the conversion sites and go to it for the calculation, but make sure that you distinguish rate from temperature when this calculation is done.

Some of the common (approximate) equivalents are:
515C =   960F a common annealing temperature
650C = 1200F low temperature slump
677C = 1250F standard slump temperature
750C = 1380F angular tack/ lamination
770C = 1420F rounded tack
800C = 1470F full fuse
830C = 1525F casting temperature
900C = 1650F low temperature pot or wire melt
925C = 1700F higher temperature pot or wire melt