Hi Cathy -
Yes, there is completely opaque black glass. Take a look at my website. I just added several pieces. Only one shows any indication of a purple red and that is on the footed compote which has a very small glass tag which is thin enough for the light to penetrate. All the other pieces are too dense for the light to penetrate (which is the absolute definition of black) :lol:
I collect black Fenton glass and you can never see any color than black under normal lighting conditons. I suppose if you were to view the glass under a strong enough light source then you might see another color - red, purple, etc.
Paden City is a distinct possibility for your plate. I can look in my Paden City book later today.