Primarily Petroliana Shop Talk Forums Shop Talk Petroliana Forums General Petroliana Discussion Chalky White Porcelain w/nice blue&red overlay?

I have 2 porcelain signs from the 1920s where the white background has lost their gloss and are chalky to the touch, leaving white residue on my fingertips when ran across the surface. But the blue and red porcelain lettering that is overlayed on top of the white, although gloss cracked, is fully glossed and real nice deep colors.

Anything I can or should do to these signs to help preserve them? Would like to stabilize the white without hurting the red and blue.

I usually only have them cleaned and waxed,don't get them overly wet,old white will Osborn water and erodes more ,compromising top coat ,and makes chalky streaks

So I can wax them without hurting anything. That is good. They are kept inside, but didn't know what I could do with a sign that had both chalky porcelain AND very nice glossy porcelain all on the same side.