[Boatanchors] carbon resistor wattage ratings

[Dick KF4NS]

Can somebody set me straight on what is acceptable as regards surface 
temperature related to wattage rating of carbon resistors?

After I calculate the proper rating using the standard power formulae, 
I then choose the next higher standard wattage rating and after 
placing the resistor in circuit I use a temperature probe to check it. 
In a recent example, I found P=.196W so I needed a 1/4W resistor but I 
only had a 1/2W and the temp probe gave me a reading on that resistor 
of 50deg C (122deg F). To the touch, that feels too hot. I cannot keep 
my finger on it for very long. I recalculated the I_ squared_ R and 
again it came up with .196W so 1/2W should be fine.

Please enlighten me.
Thanks and 73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!