Re: Gardiner is now releasing unedited concerts on CD after the concert
- From: Alan P Dawes <alan.dawes@xxxxxxxxxxxxx>
- Date: Thu, 9 Feb 2006 15:11:17 +0000 (UTC)
In article <1pKdnbOX76J14nXeRVn-uA@xxxxxxxxxxx>,
William Sommerwerck <gizzledgeezer@xxxxxxxxxxx> wrote:
On 9th February we shall be recording the first half of the concert,
i.e. the two symphonies: during the 2nd half of the concert the CDs
will be pressed so that the audience will be able, for the price of
£10, to take home a tangible memento of what we think is going
to be a very special evening.
Might I be picky?
These are not "pressed" CDs -- they're burned. That means they will not
have the theoretically indefinite life of a pressed disk.
That is a fallacy.
1) 'pressed' audio CDs have aluminium ( a highly reactive metal) as their
reflective layer which limits the average lifetime (ie before even
interpolation is unable to cover up errors) to around 25 years. This was a
commercial decision made in the 1970s by the consortium lead by Philips
that produced the audio CD specs. Surprise, surprise the largest
manufacturer of aluminium, DuPont, was a member of that consortium.
2) CDRs use silver, gold, platinum or an alloy of these for the reflective
layer which if they had been in the original specs for 'pressed' audio CDs
would have increased their liftime many times over.
Thus for a properly manufactured, used and stored 'pressed' audio CD the
main factor determining its lifetime is dependant on the choice of highly
reactive aluminium for its reflective layer.
3) This is not an issue with CDRs but they do rely on the stability of the
dyes used to create the different reflective patches corresponding to the
'pits and lands' of a pressed CD and also depend on the accuracy of the
burning process. Although the classes of light sensitive dyes are well
known the actual formulations that each manufacturer uses is a commercial
secret. With ever increasing demand for faster burning speeds the
formulations have had to be 'tweeked' which sometimes has an effect on the
stability of the dyes even after 'burning'.
4) Advances in the CD burners means that they are tolerant to a variation
in the dyes betweenmmanufacturers but this does not mean that they will
produce CDRs of optimum quality and lifetime will be reduced.
However a research chemist in the industry informs me that potentially the
dyes once 'burned' are very stable so that a CDR formulation matched to a
high quality industrial CD burner which has been correctly calibrated will
produce CDs that have a much longer lifetime than 'pressed' audio CDs.
Whether or not this is the case with those produced of this evenings
Gardiner concert only time will tell. Perhaps those on this group who
purchase the CD with report back in 25, 50, 75 and 100 years time :-)
Alan
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- References:
- Gardiner is now releasing unedited concerts on CD after the concert
- From: Thornhill
- Re: Gardiner is now releasing unedited concerts on CD after the concert
- From: William Sommerwerck
- Gardiner is now releasing unedited concerts on CD after the concert
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