I talked to a friend this week who said that
his brother-in-law sealed his pond with liquid
alum by spraying the banks as it receded. Any
of you experts ever heard of this?

Leverne Barnes

There are lot's of things I have never heard of & this is one. I'm no xpert but my guess .. either your friend is pulling your leg or his brother-in-law is pulling his.

BTW I've been to the McMinnville Carrier plant. Nice country!

Liquid alum is available but I'm not sure of its ability to seal walls of a leaky pond. It may work as long as the treated area stays covered with water. When soil dries out the seal is lost.

Aluminum sulfate (alum) is used to clear turbidity caused by clay particles in ionic suspension in a pond. Could be your source is thinking of bentonite, which can indeed be used to seal minor leaks in a clay pond, and can even be added when the leak is below water level.