Does string tension change...

[John Flynn]

This is kind of a curious, physics/metalurgy question. As strings age and stretch out, but then keep getting tuned back to pitch every time they are played, does overall string tension increase, stay the same or decrease? Put another way, does it take more, less or the same tension to get older stings to a certain pitch, than new strings?

[Martin Jonas]

Theoretically, an old string takes very slightly less tension to get to pitch than a new one, but I doubt it's even measurable. A perfectly elastic string would stretch under tension and would return to its original length and diameter when the tension is released. Steel is pretty close to being perfectly elastic, but there is nevertheless some plastic deformation after repeated cycles of stretching and contraction. Thus, an old string is a tiny bit longer and a tiny bit thinner than a new string. And as we all know, a thinner gauge has less tension at pitch.

However, this has nothing to do with why strings go dead -- that's because of surface corrosion and loss of uniformity through uneven stretching. Those factors don't affect overall tension, but they do affect tone, and particularly so in double-strung courses where differences stand out more glaringly.

Martin

[Salty Dog]

Whether strings really stretch or not is not a universally accepted fact on the Cafe (some think it just takes some time for them to slip and slide into a comfortable position). More important is that your mandolin is a living creation of wood and other materials that is constantly changing size and shape depending on temperature and humidity and who knows what other factors. There is also that mysterious factor of "warming up" the instrument and the player tnat may or may not be related to the ambient room conditions.

[pjlama]

Strings lose elasticity and become harder as to wether or not they require more tension to tune I don't believe they do they just feel like that because the elasticity is gone. I have aboutsolutely no scientific basis for my theory but I played bass for a million years and because the scale length is so long you can actually feel this happening. On the mando the short scale and high initial tension masks an obvious feeling on bass. Just my .02 http://www.mandolincafe.net/iB_html/non-cgi/emoticons/tounge.gif

[GTison]

an old string takes very slightly less tension to get to pitch than a new one,[QUOTE]

I guess that's why it harder to tune them the slightest movement of the tuning key (less CHANGE in tension) and the string pitch changes more than when the string is new. ie. Dead strings are hard to tune.

[Paul Hostetter]

Dead strings are dead (and harder to tune, etc.) because they are no longer true and symmetrical over their entire vibrating length. They become thin in spots, such as where they get played the hardest, or where sweat corrosion eats into them, and can't vibrate uniformly anymore. If you tune a string up and up and up until it finally breaks, you can bet it stretched thin somewhere, and that's where it popped.

[mandolooter]

[QUOTE] And as we all know, a thinner gauge has less tension at pitch.

I thought it was just the opposite... http://www.mandolincafe.net/iB_html/non-cgi/emoticons/rock.gif

[Martin Jonas]

[QUOTE] And as we all know, a thinner gauge has less tension at pitch.

I thought it was just the opposite... http://www.mandolincafe.net/iB_html/non-cgi/emoticons/rock.gif
Just consider the fact that light strings are tuned to the same pitch as heavy strings, but put less pressure on the top (and on the finger) to see that I got it the right way around.

Martin

[mandolooter]

ok, agreed...but its all relative to the note being tuned and the scale length of the instrument as to the amount of tension the string will be under. A thinner gauge doesn't automatically garentee less tension since wound strings have varying core sizes and different manufactors use different compositions of metals in there strings. A quick check will confirn that the same "size" doesn't mean the same tension. I was a bit too vague in my reply, I appreciate the correction.

[Martin Jonas]

A thinner gauge doesn't automatically garentee less tension since wound strings have varying core sizes and different manufactors use different compositions of metals in there strings. A quick check will confirn that the same "size" doesn't mean the same tension.
True, in particular in respect of the difference between roundwounds and flatwounds. The discussion here was about changes in a string as it ages, so differences in construction don't come into it.

Martin

[mandolooter]

yea I know...darn...hijacked another one didnt I! http://www.mandolincafe.net/iB_html/non-cgi/emoticons/sad.gif

[mandroid]

metals work harden then crack,a string, under tension, releases the tension when it breaks. , all is going normally when it breaks at the bridge.