Vinyl-repeating a track. Damaging?

I had mentioned to a friend what I had read regarding the temperature reached by the stylus in contact with vinyl - at the bottom of this needle express faq link - "As the stylus passes over the record surface, the record grooves are being subjected to a force of over 14 tons per square inch. This tremendous pressure results in the vinyl being subjected to temperatures as high as 300 degrees Fahrenheit. This momentarily melts the vinyl as the stylus passes by."

We assumed that the momentary melting is followed immediately by cooling/hardening to precisely the pre-melting state. But then we wondered what if this was not true and the vinyl is actually temporarily more susceptible to damage. I will sometimes repeat a track and.........am I nutz? (Diplomacy appreciated but not mandatory )

 

I repeat tracks periodically, heck years ago I used to play the same track over and over, and over. I never heard any sonic degradation, perhaps my wooden ears can't tell the difference.

 

Well, just from a logical point of view, of course it isn't possible that your just-played record is still anywhere near 300 degrees Fahrenheit after you play it (if it even gets that hot while it's played, which I doubt). I know one isn't supposed to put one's fingers right on the grooves, but I'm sure we've all done that on occasion, by accident, when removing a record from a turntable. When that's happened, has the record even seemed warm (much less burned your hands severely)? I've never noticed anything along these lines.

 

Oh, since I really didn't answer the question posed:

I really don't know if it's damaging to play the same record repeatedly (any more than waiting in between plays). It's certainly a myth that's out there. If there's any truth to the myth, I doubt it's because the vinyl is in any sort of melted state right after it's played.

 

I remember reading many years ago that you should let your records "rest" for 24 hours before playing them again. I might have seen it in TAS, but I'm not sure.

 

"the needle, and the damage done" ?

Quote : (Diplomacy appreciated but not mandatory).

I have long wondered why LP's weren't provided with at least a 1/2" of lead-in. Even for careful people that tiny 1/4" or so that was normal must have been handled accidentally quite often. I used to get so frustrated when I'd hear a crackle or pop on the first note of the first track.

 

Hmmm...I guess I'll take the cautious route and only repeat if it's of dire emotional need.
This will also give me the opportunity to sit on my rear longer without getting up...thats gotta be worth something.

Thanks Guys

 

Presumably, the high temperature is confined to the tiny area at the point of contact between the stylus and the groove. Don't forget that all that temperature really means is how much energy the particles in the vinyl have. Having just been in contact with the relatively fast moving stylus at incredible pressure (although the down force is small, the area of contact is miniscule leading to large pressure) it is no surprise that the vinyl will momentarily be at a very high temperature at the point the stylus has just passed.

Having said all that, the increased temperature will not last a significant ammount of time and I doubt that replaying the groove within a few seconds will have any more a detrimental effect than playing it after a night's rest - I may be wrong though......

 

I'm thinking the same thing. If it reaches those temps, it would have to be for an extremely short period of time. By the time you move the needle to repeat it, it's probably back to square one.

 

Nice link. The last two posts are almost right. Here is the deal on vinyl and distortion due to playing. First, remember that it is the stylus that is in constant contact with some part of the vinyl and even in the case of the tiny stylus only a very small portion of it is in contact. Most stylus tips a diamond and diamond is an excellent thermal conductor, so the heat quickly travels from the point of contact to the whole stylus tip which helps lower the temperature of the stylus tip as a whole. Second, As already said each small bit of the groove that comes in contact with the hot part of the stylus does so for a very short period of time so there is only limited heat transfer. Third, just because something comes in contact with something hotter does not mean that there is instantaneous heat transfer. Vinyl is a very poor thermal conductor and does not quickly spread the heat as the diamond does. So there will be only very limited local heating in the vinyl and for all of these reasons I too doubt that the vinyl reaches 300 F at anytime.

Now as to replaying the vinyl. Vinyl is a thermoplastic. All thermoplastics that I know of have a memory to some extent. What that means is that if you heat them up (to some extent, but obviously you can over do it) they will change their shape but will return to there normal state as they cool. However, the path of the shape change on heating and the return on cooling are usually not identical (this is called hysteresis). So most of the shape distortion due to the heating is gone in matter of seconds but some of it may take hours or days to recover.

Having said all of this about heating effects if you have some of the first series of MoFi LP's that were pressed on the semi transparent JVC vinyl back then, MoFi actually advertised that you could play this vinyl time after time with no ill effects because the JVC vinyl was hard enough to withstand the pressure of the stylus without mechanically distorting. Now at the molecular level both thermal and mechanical distortion amounts to the same thing - imparting energy to the molecules in the vinyl. MoFi believed that it was the mechanical effect of the stylus on the vinyl that cause shape distortion not the thermal effect of the stylus. Food for thought.

 

Indeed!

 

This is all very interesting. Does the needle take time to heat up, or will it reach around 300F on the very first song you play? I guess I'm assuming that the needle heats up as a result of pressure and friction, which makes me wonder if this becomes worse the longer your needle is in contact with the grooves.

 

Me too.