THE LACQUER DISC
Over the years, since the days of wax, recording blanks have been called by
various names including "instantaneous discs", lacquers", "acetates",
"soft-cuts" and others. If there is a "proper" name, it is probably
"lacquer" because of the fact that they are lacquer coated with a compound
of cellulose nitrate, and acetate had little to do with it, although it
has become a common name for a lacquer coated disc, and many professionals
still use the term "acetate". Habits are hard to break.
The term "waxing," still persists to this day, even though actual wax is as
out of date in disc cutting as the horse and buggy is to the automobile.
In the "bad old days" of recording, there was no magnetic tape and the
recordings had to be cut originally on huge thick blocks of warmed,
essentially beeswax. Modified versions of the old solid block of wax were in use until not long before World War II.
With the acceptance, in the early to mid thirties, of the much more
satisfactory lacquer-cutting process, wax went the way of the Dodo bird.
Thus, the final product before "processing" became a single lacquered disk
onto which the actual recording grooves were cut.
If you are old enough to ever have made an instantaneous recording, those
one-of-a-kind records that studios, department stores, vending machines and
the like made for you on the spot, you have seen a lacquer disk. It is made
of metal (although the very cheap ones had a paper base), usually aluminum,
coated with a thin layer of black, smooth, shiny lacquer. For professional
master work, the lacquer surface must be perfectly even... just like a
black mirror, and as a matter of fact, you can actually see a good
reflection of yourself in a lacquer!
Different grades of "blanks" were offered by the manufacturers,
distinguished by the evenness of coating and thickness of the metal itself.
Simply put, all the discs of a given grade started through the
manufacturing process the same way, but subsequent inspection determined
the quality level that the disk met before it was shipped out of the
plant... a "double face master" being the highest level sold for the
highest price. A disc with a blemish on one side, but otherwise master
grade would be a "single face master" and sell for less. More blemishes
and defects produced lower quality levels that sold for less and less down
to the level of the home recording user. Needless to say, for the making
of commercial pressed records or radio transcriptions there was only one
standard - the best that can be had for the purpose.
THE DISK CUTTER
A high quality professional disc recording lathe system is very impressive,
to say the least... accurately controlled to produce grooves that lie
precisely even, next to each other, and such that the depth of the groove
being cut will remain uniform and exactly as set, throughout the recording.
The mastering engineer controls all aspects of the overhead cutting mechanism, which extends from the outside edge, across the record, to the
center pin, like a bridge over water, and from which the recording head
with its stylus is lowered to the record surface. The spiraling grooves
are cut by moving the head very slowly, across this bridge, usually by a
type of screw feed. Think about a home phonograph playing a record, where the arm follows or "tracks" the pre-set grooves in the record. A disc recorder working upon a blank disk, has no such thing to guide it's motion, and so it must be mechanically moved by a special mechanism to cut spiral grooves. Provisions are made to allow speeding up the mechanism to make the faster spirals at the beginning and end of the record, as well as disengaging the feed-screw drive to permit making a "lock" groove at the
end of the record. In earlier days, or with less automated professional
equipment, the mastering engineer usually did this by turning a small hand operated crank to speed up the spiraling process.
The record grooves are very small, measuring on the order of 2 mils
(thousandths of an inch) for microgroove and about 5 mils for coarse groove
recordings (transcriptions and 78's). So that the mastering engineer can
look at and measure this tiny area, professional disc recording systems
come with attached calibrated microscopes, that can be swung over the
groove while the record is being cut. Through the microscope a good
mastering engineer can quickly determine if the cut is smooth and of the
right depth with the grooves far enough apart so as not to interfere with
each other. (Sometimes the pattern of one groove, cut too close, may
distort the wall of an adjacent groove, giving a strange almost ghostly
"echo" that can be heard just before the first sound or after the last
sound on some records.)
The continuous thread of cut material that the stylus throws off as the
groove is made is called by a few names... chip, swarf, thread and probably
a few others, although "chip" was probably the most common. Most home disc
recording enthusiasts ran afoul of this exasperating byproduct. On
occasion, it would throw itself nicely to one side and lie flat on the disk
in neat rows out of harm's way, but far more often, if not attended to, it
would entangle itself on each turn with the chip cut on earlier turns.
Catching under the stylus, it quickly builds a rat's nest of tangled
material which ruins the cut since, while recording, you cannot lift the
stylus away from the record in order to clear it without interrupting the
recorded sound and the groove itself. "Chip" accumulates static
electricity as it is cut from the groove, and it sticks obstinately to
anything and everything in sight, but mostly to the uncut lacquer surface
that the cutting head is moving towards! A dry paint brush was usually
used to push the chip well out of the way of the advancing cutter head.
Chip is flammable, and can, if a quantity of it is burned, produce a
surprising amount of acrid white smoke. Practical jokers working for radio
stations were known to take the chip pot from the disc recording room, and
set it inside the door of an announce studio just as a long newscast had
started, tossing a match in the pot and let it fizzle and sputter producing
volumes of smoke to fill the studio to the exasperation of the poor news
reader who desperately tried to keep his composure!
The solution to the chip problem for the professional was fairly easy. A
small flared pipe mounted near the inside edge of the cutting head was
connected to a vacuum system. This drew in the chip, swallowed it whole,
and captured it into a large bottle of water for flammability protection.
The chip nevertheless can still make agonizing trouble. Many a record
master has been spoiled by chip at the last minute when all else was