Efflorescence on Travertine

Q: My travertine pool coping has some salt water damage (sweeping dust) and we want to seal it. What kind of acid should I use prior to use the sealant to eliminate the salt that has already filtered in?

A: It sounds like you are experiencing Efflorescence.

Travertine is a very acid-sensitive material and it's highly
recommended not to use an acid-based cleaner as it could
have a noticeable effect on the surface of the travertine. In some
cases, the affect is not noticeable on a highly-textured surface,
so it's best to test on a small area first. (DuPont StoneTech
Restore Acidic Cleaner can be purchased
here: http://amzn.to/1pR3rYD)

If you'd rather try a different route, you can sometimes remove the
salts using a plain nylon pad and some elbow grease.