some radiators don't heat up all the time

john_216

I have a steam boiler that is in good shape. I have 10 radiators through out the house. All have new air valves and are pitched properly. The house heats up evenly almost all the time. Each radiator getting sufficently warm. However, on these cold snap days that we've had in Jersey these last few weeks, 2 of the radiators don't heat all the time. It's the same two.They can stop giving heat for a few days and then start again. One on the second floor and one in the kitchen. The boilers has been cleaned and the pressuretrol is set correctly. Could it be the cold weather? Any ideas? Also if I strip the paint from the radiators, is there any type of paint you recommend that would not have the effect of insulating them.