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Posted by Bill Vermillion on 01/11/06 04:45
In article <dpvt8829q9@news3.newsguy.com>, <phil-news-nospam@ipal.net> wrote:
>In alt.video.dvd.tech Bill Vermillion <bv@wjv.com> wrote:
>
>| I know there is no carbon black in CD/DVD production. I was
>| talking about the time I was in a pressing plant and I did refer
>| to 45s and LPs. It's amazing how good records sounded when you see
>| the way they are made with so much hand labor.
>|
>| Slap the label down, put on a hunk of black plastic, lower the
>| stamper while you inject steam into the plates backing the
>| stampers, let it sit for about 7-10 seconds, hit the cold water too
>| cool the plastic, raise the stamper, lift out the disk.
>|
>| If you didn't let it sit long enough or get it hot enough you got
>| 'non-fill' where the plastic did not go fully into the grooves
>| which gave you a noisy recording because of the small air-spaces
>| that never got plastic.
>So maybe that's what the big record manufacturers like RCA were doing
>wrong. Probably letting it sit for 3-5 seconds to up the production
>rates. That and the "debris" often found molded in. RCA was the worst
>I encountered, but many others were fairly bad (even DG at times).
RCA varied in quality over the years. As plastic prices went up
all the manufacturers tried to find ways to make things cheaper.
Pick up an LP from the 1950s and heft it and compare the weight to
LPs from the last years they were really popular.
Most of the current new LPs promote the fact that they are on heavy
vinyl - and ISTR that its 185 grams [but don't hold me to that]
There seem to be more and more of these coming out - and a lot of
the classic rock LPs are coming in from Europe on heavy pressings.
The later RCA LPs had a thick edge that sloped down to the thinner
playing surface and sometimes a changer would slide down missing
the lead-in groove. That may have been their 'dynagroove' process.
If there was 'debris' it could easily have been that the plastic
was not heated enough - and/or the regrind was not pulverized
enough and then not heated enough.
Regrind is recycled vinyl. The flash trimmed from the edges is
saved and reground. But some companies also used old unsold
stock and punched the labels out and reground that.
The problem was if some screwed up and you got part of the label
into the regrind things went down hill.
Talking with an engineer at a Columbia pressing plant [not sales
hype but as an engineer] he told me they found they could make
quieter disks with a percentage of regrind. He could not tell me
the exact amount as that was sort of a trade secret. But I got the
impression it was in the 5% to 7% range.
Then there were those companies who used injection polystyrene.
The sounded good but you needed to make sure you had good stylus
and did not track them too heavily or you'd practically peel the
high end of the grovves.
Record companies that sent those to radio stations had to send many
copies if they wanted to have the station keep them in rotation.
And somewhere in my piles of 'stuff', I have a plastic biscuit that
has Columbia labels on each side - just as it would look before it
was in the press. I tend to wind up with weird stuff like that.
Bill
--
Bill Vermillion - bv @ wjv . com
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