[Dixielandjazz] Recording CDs

[Andy.Ling at Quantel.Com]

Bob Ringwald asks :-

> Someone recently mentioned here on the List that he has had trouble with 
his 
> homemade CDs deteriorating  after a few years.
> 
> Here is a question for you experts on the List.  Is this because they 
are 
> burned using a different process then the professional CD manufacturing 
> companies would use?
> 

If by professional CD manufacturing, you mean a proper "pressed"
CD then the technology is very different.

CDs that you burn at home use a dye in the plastic. The burning
process changes the dye so that is reflects the light differently.
This means the reading laser can detect all the little burn
holes and so read the data.

CDs that are pressed have a thin layer of foil which has lots
of dots pressed into it, a bit like pressing an old vinyl record.
These dots reflect the reading laser differently and so lets
it read the data.

The dyes used in the first process can fade. This can happen
faster if the CD is heated. If this happens too much then the
laser can't find the burn holes so can't read the data.

The foil used in the second process can "creep". This takes
much longer than the dye fading, but does happen. The creep
can cause small pin holes to appear in the foil and so cause
the CD to fail.

So neither system is 100% reliable, but the pressed CDs usually
last long than the ones with dyes in.

Modern CD players are better at coping with these errors. Also as
CD players get older, the laser deteriorates. Which makes it harder
to read the CD. All this means that Some CDs will fail completely
and some will only play on some players.

I have had both types of CD fail, but not very often.

Andy Ling