Early CD question

[Megaman00001]

I've noticed on some CD's i have from the early 90's(back when they were just getting started) that underneath them you can see where the data ends like modern day CD-R's. My questions are 1. When did they come out with the ability to put a shine on the bottom so you can't see where the data ends? 2. What is the process/material they use nowadays that puts a full shine underneath professional made CD's that makes it impossible to tell where the data ends?

[jman98]

Getting started in the early 90s? You need a history lesson! I'm showing my age here, but I bought my first CD player after graduating from college in 1986 and CDs had been commonly available for at least a year if not 2 at that time. By 1990 the entire Beatles catalog had been out on CD for 2 years and pretty much everybody who was anybody had put out their past recordings on CD. I remember being really excited to have my first CD player as I thought that records just sucked. US pressings were generally awful with low quality vinyl and surface noise was a constant problem.

I can't answer your questions as I have no idea what the answers are. But I can tell you that some manufacturers still make audio CDs where you can see where the data ends.

[Midzuki]

I don't know the answer to your question, but jman is right ---
the CDDA technology is older than you used to think
--- I saw and heard an Audio CD for the first time in 1983.

[SLK001]

The OP is talking about CD-Rs (at least that was my first impression). The material underneath that makes them "shiny" is aluminum. As for the first question (which I don't really understand), might I suggest paste wax?

[disturbed1]

1. When did they come out with the ability to put a shine on the bottom so you can't see where the data ends? 2. What is the process/material they use nowadays that puts a full shine underneath professional made CD's that makes it impossible to tell where the data ends?

It's a different dye technique today compared to what they used to make. Think of blanks as being 4 layers. Plastic top, tin/aluminum, organic dye, plastic bottom. The laser heats the organic dye which causes a phase change. That's how the term burn came into play. Pressed discs are 3 layers. Plastic top, a stamped piece of tin/aluminum, plastic bottom. As time went along refinements where made in the plastics area, dyes, pressers, and lasers themselves. Today these materials are manufactured cheaper -not just $$ wise either

Megaman00001 is spot on with the time line. I paid just over $300 for a 2x SCSI CD-R burner in 1994/95. FWIW $800+ for my Pioneer A03 6 years (has it been that long ) ago.

For #2, I don't know. Taking a guess, I'd say they changed the reflective layer properties. I miss how pressed CDs used to almost look like a record, you could actually see the little grooves.

[Number Six]

I miss how pressed CDs used to almost look like a record, you could actually see the little grooves.

I believe that this is exactly what the OP is asking about. I don't think that he is asking about CD-R.

[yoda313]

Could they have changed the size of the pits of the 1's and 0's on the cds themselves?

I mean I guess they can't completely change them and still call them cd's though right? Technically they'd still have to play on the very first cd players in order to be called cd's don't they?

But I am guessing if they changed the pit size then that would be why you wouldn't be able to see the grooves anymore. Just how dvds have infinitely smaller grooves to hold more data than cds and bluray more than dvd.

Or am I going down the wrong path here?

[redwudz]

I believe the 'grooves' are already molded onto the top surface of the bottom polycarbonate layer in a CD RW disc, to give something for the burning laser to follow. Maybe in the older discs they were more obvious. I believe the 'rainbow' defraction colors you see on the bottom of the disc are from the edges of the 'grooves'.

With a CD, there is no polycarbonate top layer like a DVD, just a lacquer coating, then usually a second layer that has the surface printing. Anyone who has had the misfortune to try writing on a CD with a ball-point pen may find out how thin the lacquer surface really is.

More info from Wikipedia: http://en.wikipedia.org/wiki/Compact_disc

[jman98]

Could they have changed the size of the pits of the 1's and 0's on the cds themselves?

I mean I guess they can't completely change them and still call them cd's though right? Technically they'd still have to play on the very first cd players in order to be called cd's don't they?

But I am guessing if they changed the pit size then that would be why you wouldn't be able to see the grooves anymore. Just how dvds have infinitely smaller grooves to hold more data than cds and bluray more than dvd.

Or am I going down the wrong path here?

Well, this has nothing to do with the original poster's questions. However, you have stumbled onto how 90 and 99 minute CD-Rs are made. That is the technique they use to fit more data on the disc - the size of the pits are smaller. That's why 90 minute CD-Rs are more reliable and easier to burn than 99 minute CD-Rs - the pits on 90 minute CD-Rs are closer in size to that of 80 minute CD-Rs than on 99 minute CD-Rs.

[yoda313]

@jman98 - intersting. Thanks for the tidbit.

[SLK001]

Well, this has nothing to do with the original poster's questions. However, you have stumbled onto how 90 and 99 minute CD-Rs are made. That is the technique they use to fit more data on the disc - the size of the pits are smaller. That's why 90 minute CD-Rs are more reliable and easier to burn than 99 minute CD-Rs - the pits on 90 minute CD-Rs are closer in size to that of 80 minute CD-Rs than on 99 minute CD-Rs.

This isn't really true.

The way that the 90 and 99 minute CD-Rs are made is that they push the envelope on the pitch of the spiral groove of the glass master. This makes the overall length of the data groove longer, so more data can be written to the disk - but the size of the pits do not change. Some drives may not be able to play a 99 minute disk because maybe they can't step as precisely as needed. The CD player in my car can't play from the start of a 99 min disk.

As for reliability of either, well, they both violate the CD RED BOOK (rather badly, too), so using these sizes is a hit or miss proposition.