Odd stirbar question.

[frod1963]

So I used my stirplate for the first time last night with a Belgian Trappist WLP500. I used a small magnet from a computer hard drive that I believed to be stainless. My starter seemed to be end up a weird non light DME color and after I pitched "dumb" I noticed that the stir bar had turrned black. Is this the non stainless reacting with the starter or the coating coming off the bar?

Thanks in advance for the help.

 

[Bobby_M]

Stainless is not magnetic so there's no way it would be stainless. Get yourself a proper teflon coated stirbar.

 

[frod1963]

Thank you sir as I figured. Sooo on that note, did bare steel previously star san'd "magnet" affect the beer in a dangerous way ??

 

[Bobby_M]

Good question. I'm thinking that was some kind of nickel plating. http://en.wikipedia.org/wiki/Nickel#Toxicity

Whether it's a problem is completely a mystery to me.

 

[DavidHawman]

Stainless is not magnetic so there's no way it would be stainless. Get yourself a proper teflon coated stirbar.

That is not entirely true. Depending on the type of stainless steel it could very well be magnetic. However, I still would not use a hard drive magnet as a stir bar.

http://www.physlink.com/Education/AskExperts/ae546.cfm

 

[beerthirty]

Hard drive magnets are often used to drive stir bars, but not used to stir the contents. Bobby is correct in part. SS is seldom magnetic but can be depending on the blend of steel to chromium. Will it affect the beer, doughtfull. I don't think the small amount of dissolved metal would be noticeable.
As Bobby suggested get a real stirbar for your next batch. We are talking about a starter but at the same time we want to make the best beer we can.

 

[Yuri_Rage]

The magnet is most likely a neodymium magnet. They are usually nickel plated, like Bobby said. If the magnet wasn't plated, then the corrosion is likely iron oxide.

While it's possible to get a weak magnetic charge on some stainless alloys, it's highly unlikely that a strong magnet would be made from stainless or have any stainless parts.

Teflon stir bars only cost a few bucks. Look at science surplus stores or eBay.

 

[frod1963]

Thanks for the info. The only reason I used this bar is because I simply for got to purchase real Teflon coated bars on my last mega order. I will post a quick note after I keg explaining any off flavors.

 

[Bensiff]

Magnetic stainless steel is that which contains no nickel, chromium only. This would by your 400 series stainless. You will see such stainless advertised as 18/0 where the 18 represents 18% chromium and 0 indicates 0% nickle. It has a low level of magnetism good for things like magnetic induction cooking, but you won't see it used for a stir bar or magnet like others said.