How do cdrw's work?

[CuBie]

Hi all, i've googled this but i cant find an answer.. I presume that they have multipul layers and everytime u erase them it burns off a very thin layer off of it?

Also, if this is true ^^ how many layers do cdrw's have? Like how many times can u erase them b4 there buggered?

Chris.

[gamehead200]

I think the number of layers on a CD determines the rewrite times (If you buy CDRWs in bulk, it should be on the box...)

[XtremeMaC]

most of the time they say 1000 times...

[Chaosratt]

I dont have a link to the article, but if I remember it right it goes like this.

A "burnable" cd actually has a special ink that is in the cd. This ink is normaly disperesed and creates a very shiny surface. When struck by the laser in your burner it heats up momentarily to over 600F and changes shape, creating a microscopic spot that is no longer reflective. This creates the same pattern that is on a normal CD, maily the little 'pits' that the laser reads as a '1'. The reflective area being a '0'

CDRWs have ret another type of ink that when the laser hits it at a differnt power level, it melts completely and disperses again. It is not perfect however and constant re-melting it eventually looses its ablility to function properly, hense why they have a warning that says they cant be used more than X times. It is generaly safe to use a CD past this level, but dont be supprised if you have corruption issues.

Sorry if you didnt understand this, the article I saw explained it better, I'll have to find it again.

[Ideas Man]

Did all that googling and didn't look at HowStuffWorks.com? This article should answer your question .

[paul3vanz]

howstuffworks.com is an amazing site i love it, full of loads of useful things. i've learn't more from that site than i probably did at school!

[Ideas Man]

LOL, still am.

[CuBie]

I think the number of layers on a CD determines the rewrite times (If you buy CDRWs in bulk, it should be on the box...)

Thanks ^^..

and Thanks Chaosratt for the discription and Ideas Man for the really useful website.. Anyways im off to a maths exam ..

Bye!

Chris.

[astra12]

Read this for an insight.

CD-Rs and CD-RWs, like all CDs, are made up of a polycarbonate substrate, a thin metal coating, and a protective outer layer. In a CD-R, a layer of organic polymer dye between the polycarbonate and metal layers serves as the recording medium. The composition of the dye is permanently transformed by exposure to a specific frequency of light. Some CD-Rs have an additional protective layer to make them less vulnerable to damage from scratches, since the data - unlike that on a regular CD - is closer to the label side of the disc. A pregrooved spiral track helps to guide the laser for recording data, which is encoded from the inside to the outside of the disc in a single continuous spiral. The laser creates marks in the dye layer that mimic the reflective properties of the pits and lands (lower and higher areas) of the traditional CD. The distinct differences in the way the areas reflect light register as digital data that is then unencoded for playback. With packet writing software and a compatible CD-R or CD-RW drive, it is possible to save data to a CD-R in the same way as one can save it to a floppy disk, although - since each part of the disk can only be written once - it is not possible to delete files and then reuse the space. The composition of the dye is permanently transformed by exposure to the laser.

In a CD-RW, the dye is replaced with an alloy that can change back and forth from a crystalline form when exposed to a particular light, through a technology called optical phase change. The patterns created are less distinct than those of other CD formats, requiring a more sensitive device for playback. Only drives designated as "MultiRead" are able to read CD-RW reliably. Similar to CD-R, the CD-RW's polycarbonate substrate is preformed with a spiral groove to guide the laser. The alloy phase-change recording layer, which is commonly a mix of silver, indium, antimony and tellurium, is sandwiched between two dielectric layers that draw excess heat from the recording layer. After heating to one particular temperature, the alloy will become crystalline when it is cooled; after heating to a higher temperature it will become amorphous (won't hold its shape) when it is cooled. By controlling the temperature of the laser, crystalline areas and non-crystalline areas are formed. The crystalline areas will reflect the laser, while the other areas will absorb it. The differences will register as binary data that can be unencoded for playback. To erase or write over recorded data, the higher temperature laser is used, which results in the non-crystalline form, which can then be reformed by the lower temperature laser.

[CuBie]

Read this for an insight.

CD-Rs and CD-RWs, like all CDs, are made up of a polycarbonate substrate, a thin metal coating, and a protective outer layer. In a CD-R, a layer of organic polymer dye between the polycarbonate and metal layers serves as the recording medium. The composition of the dye is permanently transformed by exposure to a specific frequency of light. Some CD-Rs have an additional protective layer to make them less vulnerable to damage from scratches, since the data - unlike that on a regular CD - is closer to the label side of the disc. A pregrooved spiral track helps to guide the laser for recording data, which is encoded from the inside to the outside of the disc in a single continuous spiral. The laser creates marks in the dye layer that mimic the reflective properties of the pits and lands (lower and higher areas) of the traditional CD. The distinct differences in the way the areas reflect light register as digital data that is then unencoded for playback. With packet writing software and a compatible CD-R or CD-RW drive, it is possible to save data to a CD-R in the same way as one can save it to a floppy disk, although - since each part of the disk can only be written once - it is not possible to delete files and then reuse the space. The composition of the dye is permanently transformed by exposure to the laser.

In a CD-RW, the dye is replaced with an alloy that can change back and forth from a crystalline form when exposed to a particular light, through a technology called  optical phase change. The patterns created are less distinct than those of other CD formats, requiring a more sensitive device for playback. Only drives designated as "MultiRead" are able to read CD-RW reliably. Similar to CD-R, the CD-RW's polycarbonate substrate is preformed with a spiral groove to guide the laser. The alloy phase-change recording layer, which is commonly a mix of silver, indium, antimony and tellurium, is sandwiched between two dielectric layers that draw excess heat from the recording layer. After heating to one particular temperature, the alloy will become crystalline when it is cooled; after heating to a higher temperature it will become amorphous (won't hold its shape) when it is cooled. By controlling the temperature of the laser, crystalline areas and non-crystalline areas are formed. The crystalline areas will reflect the laser, while the other areas will absorb it. The differences will register as binary data that can be unencoded for playback. To erase or write over recorded data, the higher temperature laser is used, which results in the non-crystalline form, which can then be reformed by the lower temperature laser.

WOW!

Thanks for the insite! That artical explains it very well!

Cheers dude!

Chris.