Whistling A

[FiddleMkr]

I have an A string that wants to whistle regardless of all I have tried to do. I am hoping someone has a suggestion.  
     I cleaned the string(s) with turpentine followed by alcohol and a dry rag, twice. The A was dirtier than the other strings and I thought it would fix the problem. I also cleaned the bow, turpentine in a toothbrush, then soap and water, dried overnight. 
    Cleaning the string helped, but I still get a whistle at times. It seems to be more prevalent at each end of the bow versus the center. 
    It’s more prevalent with slurs (D to A, or E to A) than straight bow changes.  
    It’s been a while since I changed strings but I want to uncover why the bow isn’t gripping the string.

any ideas?

Edited June 13 by FiddleMkr
Clarification

[David Burgess]

Install a new string, and then get back to us.

There's no point in trying to diagnose problems when the strings are "false" from wear, or comtamination.

[FiddleMkr]

On 6/13/2025 at 7:21 PM, David Burgess said:

Install a new string, and then get back to us.

There's no point in trying to diagnose problems when the strings are "false" from wear, or comtamination.

What do you mean by a “false” string? 
    I get that the quick solution is to change the string, that comes from the  diagnosis of “it’s the string”. And if I worked in a busy music store this would be the answer.
       However, I don’t have a loose A to put on, and even if I did I’m trying to understand what damage could occur to a steel string from horse hair and rosin, that would make the string whistle. 
    And the other strings are as old as the A and they don’t whistle;  like the man who has one bad knee caused by old age. 

Edited June 15 by FiddleMkr
Reworded

[Shunyata]

If it worked before, make sure you don’t have a bad string.

If the problem persists, make sure that the string sits well in the nut with clean support right up to the point where the string leaves the nut.  Similarly make sure the string does not sit too deeply in the bridge.

Any dragging light contact (including with a finger) can cause whistling.  So clean, neat contact points at the nut and bridge are important.

[Shunyata]

10 hours ago, FiddleMkr said:

I’m trying to understand what damage could occur to a steel string from horse hair and rosin, that would make the string whistle.

Those strings are under a lot of load.  
 

If the string is wound, there is a complex physical structure that can give way mechanically over time.  
 

Even if it is straight steel (I guess you can still buy those) inclusions, inconsistent crystallization of the steel, micro-fractures, etc. can all give way over time.

 

[David Burgess]

11 hours ago, FiddleMkr said:

What do you mean by a “false” string?

Roughly speaking, a false string is one which does not have the same mass-per-length-unit across the entire vibrating length of the string. This can be due to uneven wear, but also be due to an accumulation of both internal and external contamination.

[FiddleMkr]

35 minutes ago, David Burgess said:

Roughly speaking, a false string is one which does not have the same mass-per-length-unit across the entire vibrating length of the string. This can be due to uneven wear, but also be due to an accumulation of both internal and external contamination.

Thank you 

[FiddleMkr]

40 minutes ago, David Burgess said:

Roughly speaking, a false string is one which does not have the same mass-per-length-unit across the entire vibrating length of the string. This can be due to uneven wear, but also be due to an accumulation of both internal and external contamination.

I did solve the problem. It was dirt (false string). I cleaned it twice before, and thought it must be clean enough, but the string was still making a dark stripe on the rag. The third time was the charm.