Yes, paper "dissolves" with a drop of water. But notice that you can find grocery bags made of "paper" that will hold several thousand times their own weight? I can tear a length of paper tape in half very easily with my fingers, but if fastened to an object that same piece of tape can lift a hell of a lot of weight.Originally Posted by lordsmurf
The bonding and shear strength of paper labels and adhesive on DVDs and other materials can be tremendous. I can show you a few white papers on such matters -- I'm no expert on paper myself but my father is an engineer, my brother is a physicist, and one thing I've learned in all my studies is that there are a lot of people out there with not very complete understandings of physics and materials engineering.
I can cut a rope easily with a pair of scissors, but that same rope can hold (and move) several thousand pounds. It depends on the physics involved. And the physics of a label on a disc are actually rather fascinating.
This isn't to say that I know that labels warp discs and thus cause the problems encountered by some people. But evidence (presented here and elsewhere) does support the following:
1) Putting labels on discs causes playback problems for some people.
2) If the problem were simply that of disc imbalance, putting some other kind of object (e.g. barcode stickers) on the DVD that would also cause imbalance, should duplicate the problem (poor or no playback).
3) Doing such tests has been done, and the imbalanced disc still plays back normally (within test parameters, anyway).
4) QED, there is something else causing the problem.
Personally, I find this test stuff fascinating and a bit fun. And having just cut myself on a piece of paper that has up until this point in time been a harmless scrap on my desk, I'm not ready to agree with your conclusions just yet.
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Where did I say storage could not cause warping? Since I'm not familiar with the storage cases mentioned, may I ask if there is any other force besides gravity being exerted on the discs? If not, that's a whopping 16.34 grams (just weighed one on an electronic scale) exerted total on the whole disc, by no means all of it at the edges. Let's see, divide that by an area of about 269.87 sq. centimeters.... really, I don't see the need for any esoteric calculations.
I'm sticking by my claim that paper can deal with far more than that, just from experience. Mortar mix comes 80 pounds each in a- you guessed it- paper bag. Moisten anything with a paper veneer, such as drywall or MDF, then lay it out in strong sunlight. It'll warp alright, lifting up the edges of the sheet, as the heated side contracts. Actually, anything made of cellulose fiber will behave similarly, which is why plywood and dimension lumber is always covered with a tarp at construction sites until needed.
The point is, paper has high tensile strength, greater than wood. Wood is made of long narrow tubes or cells called tracheins or fibers. Tiny strands of cellulose make up the cell walls, the cells being held together by a natural cement called lignin. The papermaking process removes the lignin, or most of it, and the fibers are oriented for mechanical strength. The less lignin and the longer the individual fibers, the stronger the paper. Currency is typically very strong paper. Importantly, paper is not very stable, the fibers expand and contract according to temperature and ESPECIALLY moisture content. Just like wood.
Bond this onto an unlike material with a mastic or contact cement and it'll have to be damn stiff to remain perfectly flat. Either that or the humidity and temperature will have to remain the same as when the label was first applied. Now, if you could apply an equal, counterbalancing force, there'd be no problem. However, you don't label both sides of a disc.
But we can agree to disagree. This sure wouldn't be worth having a nasty argument over. :P
[EDIT] Boy, did this ever get way the hell off topic! Sorry.Pull! Bang! Darn!