Here is a repeat of comment from the earlier Steaming At Steve's March 10,
I ran an experment with a new and unknown type of coal. This was coal that is used at Zube Park in Houston for the big engines that run on the seven and a half inch gauge track. I just could not get a decent fire going with this coal. I could not find a way to set the controls to keep steam up with this coal. So --- I ended up dropping the fire and starting over with Welch coal and then got the engine running great. It was interesting to experment but it would have been more fun if the test had been a success. My shed has four burlap bags of the coal that was tested. Clearly, I will stick with Welch coal.
This is another video with really good quality by Art.