White and Black Smoke

[NW Mailing List]

Good morning.

I am not worried about my Arrow not arriving yet and will not be posting when it arrives.

The purpose of my post this morning is to inquire as to why on many of the programs that I watch on RFD TV (Trains and Locomotives) some of the smoke is black and some is white.  What is the cause of this? Have a great weekend and thank you in advance for any responses.
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