How do I remove this brown staining on the back of this plate?


Hello Everyone!! I got a plate with daisy design on front, but it has brown staining on the back side?? Have no idea ‘what’ it is from? Have tried baking soda, lemons, vinegar, to remove it!! One of the above worked a little, but did not remove it all? Any suggestions would be appreciated!! Thanks guys!!!

q brown staining
q brown staining
  8 answers