Unfortunately, depending on what kind of photos you have and how they became stuck together (a condition we call "blocked"), they may be very difficult to get apart without further damage. We would not suggest using water to separate images that are stuck together because the pictures probably became stuck together due to high humidity or contact with water. Also, the very many different processes used for creating photographs can react very differently to water. Water will soften the image coatings and the image itself, and the dyes if there are any, and it can also damage the writing inks that may be on the backs of pictures. These could easily fade or change in water and spread into the other pictures, and also photos become very vulnerable when wet—you could end up separating layers within each photograph.

If you don’t have negatives for your photos anywhere, and the images are unique and precious to you, you should consider contacting a photograph conservator using the American Institute for Conservation’s tool for finding a conservator in your geographic area. A professional photo conservator can tell you if it might be worth testing or not. If very little surface area is stuck, and not in the area of importance (for instance, at the very edges—not in the central area of interest like someone’s face in a portrait), you might be able to do something. Don’t give up hope though, we have our own problems with this, so we try to research and study it. Also, do try and keep your negatives safe, dry, and in clean acid-free envelopes and boxes to avoid this in future!

Thanks for the reply but bad news for me. I have many photographs pasted (by accident) and I see that cannot be separated.

Same problem here..
Any solutions?