Expert: Ralph Salier - 12/21/2011

Question
Dear Ralph,

Since this is the Archaeology section and it studies artifacts over time, I was curious if you know which may last longer?

Context for my question:  My mom died, and we are putting one of those photographic portraits on her headstone to make it more personal looking.

There appears to be a debate out there about which lasts longer, the headstone pictures with steel in the center and enameled with ceramic, or pure porcelain all the way through. So I'm trying to get to the bottom of all this.

For example, in the debate those for the steel portraits say porcelain is like dropping a plate on the ground, it breaks, for example vandalism. They say having steel in the center is less likely to break. On the other hand, those for pure porcelain portraits say that although the steel ones are advertised as stainless steel in the middle, they're actually not "pure" stainless steel. It's ASTM A424 steel, or enameling steel. They say if there's any scratching, the steel underneath can corrode and then spread. They say pure porcelain all the way through won't have that issue.

Do you think porcelain or steel coated with ceramic on steel would last longer, as a picture on a headstone? Also another question, since the steel coated with ceramic pictures aren't heated as high as the pure porcelain, does that make the pictures less colorfast? How easily do things on headstones break?

Thank you for your time,
Nick

Answer
Hi Nick,

I've seen ceramic ones that are 100+ years old.  Of course they are vulnerable to vandalism, Steel ones are stainless and A242 is a type of stainless that is solid stainless and since it is stainless will not rust or corrode, even when scratched.  On the other hand the image can fade over time depending on the process.  If it is etched then it will survive longer but will not be as nice an image.  Ceramic on steel is somewhat more durable but it too can be damaged by vandalism in that the enamel can be broken or cracked.  

Personally, I would go with ceramic which is ceramic through and through and then have it covered with a plexi-rosin to protect it from vandalism and it will last a few centuries.  Ot will retain its color and image integrity.