I already posted this message in another thread today. But since it is interesting, please allow me to copy paste here! 
When I was young, there were reports of 'sacred ash' falling from Sri Sathya Sai Baba's pictures, in the nearby villages.
And, I HAVE SEEN something like 'sacred ash' which emerged from the heart of Jesus Christ (!!) and accumulated in between
the picture and the glass covering, for a few days !! People thronged the house, which was owned by a lady nurse of our local
maternity hospital in Anaimalai village. Till today, it seems a wonder to me! How is it possible?
'Google search' provided this lengthy video which was amazing! How do these events happen? :noidea:
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SOULJOURNS - HOW SACRED ASH (VIBHUTTI) POURS FORTH...[/TD]
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Our SM is dead against writing about SSB and other Gurus and so I hope this post is not deleted.
I was told that glass reacts with one kind of acid (I forget its name now) slowly and forms an ash-like powdery end-product, along with some moisture. The "ashing" photos of SSB or any other deity/guru/godman can be easily made by gently coating the outer surface of the framed photo/s with this acid and then placing them back in position. Usually such devotees are 'advised' by experts from the relative organization/Ashram to leave out the face portion of the photos. This is because the glass becomes semi-transparent after the chemical reaction cited above, especially if the miracle is to be sustained for months. In such cases the so-called "blessed devotees" have two or more similar (identical) photos and use a new one when the old one becomes too tell-tale, though they try to cover up as much of the photo as possible, with garlands, flowers from "archana", etc.
But this is a very efficient trick which makes very many gullible people (even those living abroad) fall into the net of the relative godman/godwoman/guru cult.
There are a few other methods also but those are little more costly. I quote from
An Indian Skeptic's explanation of miracles By "Anti-Guru" B. Premanand :—
Vibhuti produced from Satya Sai Baba's photographs.: Actually vibhuti does not fall constantly from the framed photographs of Satya Sai Baba. To know if really vibhuti forms on the glass, unless one removes a portion sticking to the glass it cannot be known. What is done is, ash is mixed in starch solution and sprayed on the glass except the face. The man in whose house vibhuti is forming on the photos does not permit any one to go near them or touch them. They say that if any one touches them with an intention to verify the truth the vibhuti stops forming! What is done is the top of the photo frame is hollow and is filled with vibhuti, while the glass is fitted loose. When the ceiling fan is switched on, the ash stored in the photo frame top flies and people think that really vibhuti is falling from the photos. This could be exposed by removing a part of the vibhuti pasted on the glass and see if it again forms there and by stopping the fan. In one house of an advocate at R.S.Puram, Coimbatore where this claim was made, I had to wait for more than two hours as there was power cut and only when power came, I was taken to the prayer room to see the vibhuti falling from the photos of the godman. When I came out the fan was put off, but I suddenly turned around to see if vibhuti was still comming from the photos, it had stopped!
