# My stainless steel flask and the crud inside **URL:** \ **Category:** Factual Questions\ **Created:** [March 2, 2000, 3:47pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032 "2000-03-02T15:47:00Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![mouthbreather](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@mouthbreather](https://boards.straightdope.com/u/mouthbreather)\ **Post date:** [March 2, 2000, 3:47pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/1 "2000-03-02T15:47:00Z")
I am going to a hockey game tonight (Go Trashers! 15 game losing streak! Ahhright!) so I decided to bust out the old flask to take to the game. EVERY single time I go to use it, I see that there is this blue-green colored gunk that is on the inside lip of the flask. I have to soak in hot water for a while, and then it’s as good as new. I always thoroughly clean it every time I use it. I have plenty of other stainless steel items that do not accumulate this gunk on them. It drives me nuts! It’s not mold, it’s more “chalky”, for lack of a better way to describe it. Anyone else have this problem?(the gunk problem, not the alcohol problem.) Anyone know what this might be? ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [March 2, 2000, 4:08pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/2 "2000-03-02T16:08:00Z")
Sounds like a leak between the seal & the flask. So the metal inside makes some crud. ---
**Author:** ![mouthbreather](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@mouthbreather](https://boards.straightdope.com/u/mouthbreather)\ **Post date:** [March 2, 2000, 4:24pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/3 "2000-03-02T16:24:00Z")
handy, can you expound on that I bit? I’m not following you on how a leak could cause this. Thanks. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [March 2, 2000, 5:15pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/4 "2000-03-02T17:15:00Z")
What do you put in the flask, how do you clean it and how do you store it? Does it have a screw cap? Is the cap stainless steel as well? ---
**Author:** ![InutilisVisEst](https://avatars.discourse-cdn.com/v4/letter/i/d2c977/32.png) [@InutilisVisEst](https://boards.straightdope.com/u/InutilisVisEst)\ **Post date:** [March 2, 2000, 5:16pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/5 "2000-03-02T17:16:00Z")
I’ve got a flask like that. Because it’s expensive to machine stainless steel, the threaded neck of the flask is nickel-plated brass. The greenish stuff is copper corrosion. I think you can prevent it if you clean it well after each use, dry it off, then put a light coat of vegetable oil on it. Can’t say for sure, because I generally soak the gunk off before each use like you do… 🙂 * * * Sure, I’m all for moderation – as long as it’s not excessive. ---
**Author:** ![InutilisVisEst](https://avatars.discourse-cdn.com/v4/letter/i/d2c977/32.png) [@InutilisVisEst](https://boards.straightdope.com/u/InutilisVisEst)\ **Post date:** [March 2, 2000, 5:21pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/6 "2000-03-02T17:21:00Z")
Oh, should’ve mentioned: brass is less expensive to machine if they put a little lead in it. Used to be a problem with faucets until legislation was passed. Also, my flask has a soldered-on top and bottom, and that solder might contain lead. Drink alcohol that’s been in there for a while and you could end up crazy as Caligula. Heck, you’re not even supposed to store Scotch in a lead crystal decanter for that reason. You could lead test the thing if it’s sentimental, or (probably cheaper) try to find one that claims to be lead-free. * * * Sure, I’m all for moderation – as long as it’s not excessive. ---
**Author:** ![EvilGhandi](https://avatars.discourse-cdn.com/v4/letter/e/f17d59/32.png) [@EvilGhandi](https://boards.straightdope.com/u/EvilGhandi)\ **Post date:** [March 2, 2000, 5:23pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/7 "2000-03-02T17:23:00Z")
Blue-Green colored chalky gunk, hmmmm. Possibly some copper compound caused by dissimilar metal contact between the cap and the bottle. Try replacing the seal with a rubber O ring or a slice of cork. Making sure the flask is clean and dry befor storage might help as well. Also, don’t tighten the cap all the way down, this will keep current from being set up between the two surfaces. ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [March 3, 2000, 1:20am UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/8 "2000-03-03T01:20:00Z")
Lead? Bluegreen is copper oxidizing. ---
**Author:** ![InutilisVisEst](https://avatars.discourse-cdn.com/v4/letter/i/d2c977/32.png) [@InutilisVisEst](https://boards.straightdope.com/u/InutilisVisEst)\ **Post date:** [March 3, 2000, 2:10pm UTC](https://boards.straightdope.com/t/my-stainless-steel-flask-and-the-crud-inside/8032/9 "2000-03-03T14:10:00Z")
Yeah, it’s copper oxidizing, which means there’s brass under the nickel plating, and the brass probably contains lead which can be leached by alcohol. Sorry if it sounded like blue-green = lead. * * * Sure, I’m all for moderation – as long as it’s not excessive.