Freezing CDs?

The Devil said:
That's such a non-argument.

Have you tried <insert pointless thing to try here> yet? Putting your hand in the fire, a manure sandwich, twiddling a pencil, standing on your head...
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Yet another highly constructive post from .......shall we say a........"doubter".


(Whoops, sorry D Louth :o)
 
Seeker_UK said:
I think that this has got absolutely nothing to do with physics at all. The temperature of a domestic freezer is what, -10C, -15C. Polycarbonate (ie that which has the 0s and 1s etched onto it) cannot be affected at that temperature. If it could, we wouldn't make jet fighter canopies or use it other pretty demanding applications.

Therefore, it is extremely unlikely, bordering on the impossible, that any physical changes to the pits occurs
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Polycarbonate is used for jet fighter canopies simply because it retains a very high impact resistance over a very wide temperature difference. The other side of the aluminium layer however is Acrylic, this has no way near the same impact resistance as polycarbonate especially not at low temperatures when it becomes very brittle.
both materials however will in sheet form sag under there own weight, polycarbonate being worse in this respect than acrylic.


Seeker_UK said:
OK, poor choice of words but compared to Aluminium they are pretty un reactive to heat with regards to expansion / contraction.
/QUOTE]

Actually Acrylic is a poor material choice if you wish it to be stable. It has quite a high coefficient of linear expansion;


Product..........(10-6 m/m K)............(10-6 in/in oF)
Acrylic..........................68 ...............38
Aluminum.......................22.2 ...............12.3
Copper..........................16.6 .................9.3
Glass, plate......................9.0 ...... ..........5.0
Polycarbonate.................21.5 ....... ..........12
Wood,
oak parallel to grain............4.9 ...............2.7

A piece of acrylic sheet 5mm thick x 10mm wide X 300mm long if fixed at one end
will sag under its own weight if left unsupported for several days, if it is heated,
even by the sun it will sag very quickly. If left in this position for long it will remain permanently bent.

The temperatures reached in a domestic freezer would easily have an effect on the Acrylic layer, and likely an effect on all the other layers, whether this has can have any permanent effect on the disc, I do not know. However we are only talking very small dimensional changes being necessary to affect the readability of the disc. 125 nanometers (the height of the bump) is not very high. If we take the disc to be 1.25mm thick, then the bump is 10,000 times smaller. Without some genuine scientific experimentation into any possible effects I believe the jury must still be out on this.
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I would imagine the -10 degrees of your freezer pales into insignificance with the furnace that is the dash mounted cd player in my car.

Fucking idyats.
 
DavidF said:
Yet another highly constructive post from .......shall we say a........"doubter".


(Whoops, sorry D Louth :o)
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I think he has a fair point.

Is someone telling you to freeze a CD and it will sound better any different to saying a manure sarny will help your kids grow strong and healthy?
On face value no it is no different.
 
penance said:
I think he has a fair point.

Is someone telling you to freeze a CD and it will sound better any different to saying a manure sarny will help your kids grow strong and healthy?
On face value no it is no different.
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You said it your self P.

hOw do you KNOW?

I certainly don't.

I strongly doubt it...but i don't know.



(edit ....I would say the TECHIES are argueing over the details....have you noticed???!!)



+since when did the guy put any point fairly?




:)
 
granville said:
Polycarbonate is used for jet fighter canopies simply because it retains a very high impact resistance over a very wide temperature difference. The other side of the aluminium layer however is Acrylic, this has no way near the same impact resistance as polycarbonate especially not at low temperatures when it becomes very brittle.
both materials however will in sheet form sag under there own weight, polycarbonate being worse in this respect than acrylic.


Seeker_UK said:
OK, poor choice of words but compared to Aluminium they are pretty un reactive to heat with regards to expansion / contraction.
/QUOTE]

Actually Acrylic is a poor material choice if you wish it to be stable. It has quite a high coefficient of linear expansion;


Product..........(10-6 m/m K)............(10-6 in/in oF)
Acrylic..........................68 ...............38
Aluminum.......................22.2 ...............12.3
Copper..........................16.6 .................9.3
Glass, plate......................9.0 ...... ..........5.0
Polycarbonate.................21.5 ....... ..........12
Wood,
oak parallel to grain............4.9 ...............2.7

A piece of acrylic sheet 5mm thick x 10mm wide X 300mm long if fixed at one end
will sag under its own weight if left unsupported for several days, if it is heated,
even by the sun it will sag very quickly. If left in this position for long it will remain permanently bent.

The temperatures reached in a domestic freezer would easily have an effect on the Acrylic layer, and likely an effect on all the other layers, whether this has can have any permanent effect on the disc, I do not know. However we are only talking very small dimensional changes being necessary to affect the readability of the disc. 125 nanometers (the height of the bump) is not very high. If we take the disc to be 1.25mm thick, then the bump is 10,000 times smaller. Without some genuine scientific experimentation into any possible effects I believe the jury must still be out on this.
Click to expand...

How much of an effect does cold have in comparison to heat with regard to acrylic? From what I remember at school it is quite malleable with heat but not cold, and probably more variable in it's dimensional changes though variables in heat than cold ( many CD players get pretty toasty inside, and most continents have some variables in temperature but no performance differences seem to have been noted with regard to CD replay?

Freezing acrylic in a fridge freezer will probably not produce any permanent changes to the material density or structure, and certainly not it's thickness or transparency when it returns to ambient temps. I am sure we all played with plastics at school and found how the material will try and return to it's original shape with the aid of heat, and I am pretty sure many have made an attempt to snap a CD. Its reasonably robust and capable of a bit of abuse.

Instead of freezing your CD why not try spray painting the label side black? I am sure its was documented that the label side could make a difference?

I also remember a special green pen being available! In fact did some weirdo's not believe that any old green pen would do even though the proper "green" pen's had "special" ink?

Come to think of it, many early CD's were thicker in construction than later cheaper ones, I am sure they were reputed to have heavier bass and more weighty sound, in comparison to the lighter ones which sounded a little thin?

And does any of this affect the focusing of a CD transport laser which I think is designed to allow for such small changes (IE it's focus is not on the surface of the disc but on what's underneath)?

In my opinion freezing a CD along with your tea is pointless, the most worthwhile tweak with a CD you could probably justify is the CD laith, but you would have to be a muppet to pay the price these go for.

:)

PS I am sure its the length of the bump not the height which pre determines the 0 or 1 and that such differences due to contraction or expansion caused by freezing and thawing, or slightly high ambient temperatures, will have no bearing on the transport mechanism ability to differentiate this 0 or 1 pit?

Nor to my knowledge is polished alloy more reflective when in the Antarctic under comparison to polished alloy in Botswana? ( maybe someone has Poll figures showing that audiophiles in the Antarctic enjoy a better performance due to lower CD player temps?)
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DavidF said:
You said it your self P.

hOw do you KNOW?

I certainly don't.

I strongly doubt it...but i don't know.
Click to expand...

This is completely pathetic agnosticism. No one knows there's no dragons, unicorns, flying spaghetti monsters, gods, ley lines, and all the other nonsense you can imagine. But in the complete absence of any evidence whatsoever for these things, the rational stance is that they don't exist, until evidence shows us otherwise. This is the 21st century, not the 14th. No one can ever prove a negative.

Ta to penance, rob, tones et al for rational scepticism.
 
Mr. Devil is doing this forum a great favour with his posts. Not only by upholding rational thought, but primarily because this crazy thread is the most popular this forum has had in the last few months, at least! ;)
 
Tenson said:
Mr. Devil is doing this forum a great favour with his posts. Not only by upholding rational thought, but primarily because this crazy thread is the most popular this forum has had in the last few months, at least! ;)
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I can point out some posts which aren't so rational (and certainly not such a great favour) simon but not to worry!
 
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