getting it down to the bare metal

While my '57 is stripped down to the frame I thought I'd go ahead and remove some of the rust and scales that have grown over the past 50 years. As I started to use the wire brush and then the flapper disc I notice I am removing a black tarry substance.... some kind of coating or sealer, I'm not sure. What is this stuff? Is it adviseable to go down to the bare metal?

 

would it not be someones previous job of undercoating? Cant see why you cant go down to the metal... it may take longer, but it shouldnt hurt anything.

 

heat and a s****er worked for a friend of mine.

 

AIRCRAFT STRIPPER took my 4 layers of paint 62' merc' down to bare metal in two days..warning its messy and smelly so take caution

 

I agree.. sounds like previous undercoating...
we cleaned my old truck ch***is, and under the cab before taking it to the media blaster (if it came to him already clean the rate was cheaper)
Anyway, we took a torch, and a paint s****er... put some heat to it,.. got it hot, and it rolled right off like nothing... very easy.