I am needed to know how to protect a photo of my daughter from sun fading. I want to put something different than the normal little oval picture on her headstone. I want to put at least a 5x7 in a metal frame like you would see in a home on her grave next to her headstone. Can anyone tell me the best way to do this so her picture will not fade?
Search for "photo-etching on metal" and you will find many sources. These are not super expensive. Have more than one made so you or your heirs can replace down the road.
There is a technique for somehow etching a picture onto polished stone (granite?). I saw this on a few gravestones in the Rye Colorado cemetery in August of 2016. The polished stone was dark. The etched areas reflected ambient light more, and made a recognizable image when viewed from the correct angle. I have no idea how long something like this lasts, probably a few years. Since it relies on fine detail, I expect that part to weather away more quickly than other parts of the stone that can tolerate more erosion.
I remember wondering how the process worked at the time. Alephzero mentions in a comment that this is probably laser-engraving. That is plausible from what I saw.
This seems to be popular in some cultures. The photos I have seen appear to be fired in a ceramic kiln. A quick web search finds suppliers who will inkjet print the ceramic and fire it into a porcelain photo.
Anything that survives a ceramic kiln will not fade quickly in the sun- the colors that typically fade such as the reds will be inorganic oxides rather than organic dyes.
Normally pictures used in cemeteries are porcelain pictures and they won't fade because the ceramic toners are fired onto the porcelain at high temperatures. They are sold in many shapes and sizes.
You can do a 5x7 rectangle with a frame or a 5x7 oval with a frame from www.photosforheadstones.com. They do the pictures for much cheaper than what the cemeteries charge.
If you are looking for a color photo, carbon printing is about as permanent as it gets, and the image can be deposited on more or less any substrate. The black and white version of the process uses literal carbon (lampblack); three colour separations are made with artists pigments, like for oil paintings, which are known to last hundreds of years without fading.
Unfortunately it's a labour intensive process that has become pretty niche, and probably won't be cheap. A 5x7 might be affordable though; obviously this is a pretty important photo.
If you are looking for a Standard Photo, that wont exist. Even if you use Archival quality acid-free media fronted with UV and IR filters, temperature extremes and moisture will eventually get into the space and begin to act on the paper to degrade the image. Probably even if you were to embed the image in a poured acrylic block the acrylic would eventually yellow. Because of that your best bet for long term stability would be Etching Stone, Steel or Glass.
Depending on how much you wanted to spend, and if you wanted several hundred years of stability, I think Etching a Glass pane and then laminating that pane in a glass block would keep the image fresh for a thousand years or so if it were not broken. Then you would just need to polish the block and the image embedded in it would be visible again.
please check this website. costco has acrylic prints