Stains in carboy glass?

[jajao44]

I bought a used 5 gallon carboy at a Antique shop and looked in very good shape except for a white filmy looking residue in the bottom but I figured 20 bucks good deal so I got. Let bleach soak over night shaking occasionally next day then scrubbing with a brush. Never came out. Decided to brew a graff and let it go; everything went well very active initial fermentation.
About a week later I get another carboy that has the same problem. So I try the same thing and also oxiclean. Did nothing. I decided to transfer my graff to the new carboy and see if somehow the stain is gone. Transferred and there is still a faint stain but the first carboy I bought overall looks cleaner.
I'm just worried about the new one I bought the stain on the bottom is thicker and the whole bottle was dirtier even with filling the bottle full over night oxiclean and scrubbing and soaking with 90% bleach on the bottom and scrubbing small difference. I sanitized well so hopefully I won't get a off taste or a bad batch.
Anyone have good ways to remove stains or film from glass or had similar issues?

 

[lumpher]

sounds like hard water stains. no hope for that, that i know of

 

[nebben]

Hard water stains are easy to remove. Get some CLR in the store and either let it soak or put some on a sponge or something and just wipe it off.

 

[mobly99]

I second using the CLR. That stuff is great at getting rid of hard water deposits.

 

[CereousBrewer]

I have purchased a few glass carboys at antique shops that have also had the white, milky appearance on the inside. Many times these carboys originally contained caustics or acids (amonium hydroxide or hydrochloric, nitric or sulfuric acid). If the carboys are not rinsed when empty the glass can be etched by the original chemicals, which is permanent.

I have fermented many batches of beer and apfelwein in the carboys and never had a problem. If you make sure you remove any residue that is not etching, clean and sanitize the carboys I doubt you will have a problem.