When during a wedding ceremony is the proper time to do a sand ceremony?

The sand will be thrown at you when you're coming back down the recession.

I think the sand ceremony is equivalent to the unity candle ceremony. Our minister has put our unity candle ceremony in after we have exchanged the rings, said the vows and been pronounced husband and wife and shared a kiss. Then as a newly married couple we are lighting the unity candle and taking communion. After that he will introduce us to the crowd, "May I present Mr. and Mrs. ...."

Generally, the sand ceremony occurs after the readings and vows, but before the rings, blessing, and recessional. I'm not sure how religious of a ceremony you're doing, but it's usually around the same time a unity candle lighting would occur.

Towards the end of the ceremony. After the vows have been said and the rings have been exchanged. Or atleast thats how mine was done.

I usually do a unity ceremony after the vows & rings.

Maybe you should discuss this with your officiant.