I am not an expert here but I would appreciate some advice. 

I have a part (actually an airplane wing) . It was originally  an SLTPRT part. I was able to save it without modification as an STL part and I modified its appearance so that the surface looked like stone (or whatever)    The texture of the surface did not save after I did "save new"  in the STL file format. I did go to "options" and attempted to save as "Binary" with the "Deviation" and "angle" set very low or fine. However, the details of the new texture did not translate to the new STL file. But IT DOES SAVE AS AN SLTPRT file.

The bottom line is that the appearance modification did not translate to the STL file format.

Thank You

Tom