effects of saltwater on glass.

[awvil]

how long does it take sea water to effect glass? i am curious to find out how long it takes, and what the process is.

 

[dirk49]

An extremely interesting question. From only a practical point of view, I can tell you that glass is used in marine applications such as sea strainers, which are devices that filter incoming seawater for cooling purposes. Sea strainers have been used on boats for many years. I don't know exactly how long they've been used, but I have personally serviced sea strainers that have been in use for well over 20 years. Interestingly, sea strainers not only "live" below the sea surface, (albeit in an environment with air on one side), they also frequently have a significant flow of sea water through them. Glass in itself is a peculiar material, as, I am informed by engineers, it is at almost all times a liquid. Glass in a vertical application, such as a window pane, will eventually flow to the point that it is thinner at the top than at the bottom. That will take many years to occur, but it can be verified easily with a micrometer and any pane of glass in an older house. Given that glass in it's usual solid appearing state is a slow moving liquid, one does have to wonder what the effects of another liquid in motion in direct proximity has upon it. Does it erode? Does it "Ripple" like a sand dune?
I hope this doesn't raise more questions than it answers, but it is very curious. If it is of any help at all, my experience is that glass in it's "pure" form as well as it's "Composite" form (fiberglass) is as nearly absolutely inert in seawater as anything can be.
So, why do you want to know?
Dirk

 

[awvil]

thank you for the insight. the reason i ask has to do with 'sea glass' the very smooth, sometimes rippled glass found on beached. there is a bit of a debate on how long it takes to get 'worn' into shape. so the glass here is generally from bottles. thank you very much for the info. do you know of and sites i could research this further?
matty

 

[dirk49]

Matty (Awvil),
Sorry, but I don't know of any sites. That means little, as I haven't looked for any. I've also picked up glass shards that have been "tumbled" in the surf zone, so I'm familiar with what you're looking to find out. I would guess that there are many variables involved, and that the role of sea water is probably the least significant factor. Primarily it would be the abrasiveness of the surrounding environment, such as the makeup of the sand and stone in the area. On the west coast, the sand is mostly rock particles, while in the caribean and south pacific the white sand is broken coral, which would be softer. Also, the west coast has generally more violent surf action than the east coast. All in all, it would take less time to affect the appearance of glass in the west. You might try Scripps Institute of Oceanography, or try a lapidary site. Rocks and gemstones are polished by tumbling in a rotating drum with a liquid and an abrasive to give them their luster.
Good luck!
Dirk