Re: [ARSCLIST] Hard disk drives and DAT

[Jerry Hartke <jhartke@xxxxxxxxxxxx>]

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx] On Behalf Of Don Cox
> Sent: Saturday, March 31, 2007 10:23 AM
> To: ARSCLIST@xxxxxxxxxxxxxxxx
> Subject: Re: [ARSCLIST] Hard disk drives and DAT
> 
> On 31/03/07, Steven C. Barr(x) wrote:
> 
> > ----- Original Message -----
> > From: "Don Cox" <doncox@xxxxxxxxxxxxxx>
> >> I think an archival digital format that would last as long as
> >> Sumerian clay tablets could be developed if the market was there.
> >>
> >> It would have to use physical pits rather than dye or magnetism.
> >> Possibly some kind of toughened ceramic material would be suitable.
> >>
> >> Multiple layers, as on many consumer discs, would not be practical.
> >>
> > And what happens if these Sumerian clay tablets get wet and stay wet
> > for any length of time? Most forms of mud dissolve under those
> > conditions (an argument against building "my adobe hacienda"...)
> 
> The Sumerian tablets are probably not fired, but they easily could be.
> 
> Any modern material would not be soluble in water. There are many
> specialised ceramic materials used in engineering today.
> 
> From ultrahardmaterials.com:
> 
> "There are three exceptional properties of engineering ceramics:
> 
>  (1) Their very high hardness enabling products made from them to wear
> less and last longer.
> 
>  (2) Their ability to operate at very high temperatures.
> 
>  (3) Their capacity to withstand very harsh and corrosive environments
> such as acids, alkalis and organic solvents."
> 
> The technical problem is to design a laser setup that can burn accurate
> pits in a disk of such a material. This shouldn't be that much more
> difficult than making a glass master disk.
> 
> See here for a useful summary of materials:
> http://www.machinedesign.com/BDE/materials/bdemat7/bdemat7_2.html
> 
> We can do better than shellac, I think.
> 
> Regards
> --
> Don Cox
> doncox@xxxxxxxxxxxxxx

Such a proposal is not practical. In order to read optical media in any
practical environment, the microscopic data features must have a transparent
cover layer. The thickness of this layer is 1.2 mm for CD, 0.6 mm for DVD
and HD DVD, and 0.1 mm for BD. The cover layer creates an entrance surface
that is remote from the information layer. The laser beam is out-of-focus at
the entrance surface, thereby minimizing beam degradation from dust,
fingerprints, and scratches.

Jerry
Media Sciences, Inc.