I created a frame for a custom fire pit spark catcher I am designing for my backyard.  I created the frome as a weldment part. I did half of the basic frame and then mirrored it to make the other side. I turned the bottom tube transparent so that I  could make sure the angled supports trimmed correctly.  Once I deselected the change transparency the original side became opaque again but the mirrored side stayed transluscent.  I have found lots of resources for simular problems with a face.  This is with a mirrored part.  See attached picture and file. Thank you