From: Patent Tactics, George Brock-Nannestad


Hello,

Mike, you were mostly correct, but we do not want even the smallest error to
go down in history, do we? So, in order to obtain precision:

> On 8/15/2010 10:32 AM, Randal Baier wrote:
> > Well, Mike, speaking for all the jerks out here, I'd like to know the
>> difference between the two. I certainly didn't catch that. Gee, I thought it
>> was a cut, but I guess it was a slice.

Mike:
>
> They are two entirely different machines based on two entirely different
> principles. They are as different as an inkjet printer is from a dot
> matrix printer is from a laser printer. The program showed and
> described a mimeograph but the guy the showed at that point described a
> ditto, spirit duplicator, or hectograph.

----- already here we need more precision. The Hectograph was a flat-bed
printer. You wrote or drew with special ink on a rather non-absorbent sheet,
pressed it against the surface of the jelly-like substance, and the ink
transferred (now a mirror image) to the substance. You could then press up to
100 (hekto in Greek) increasingly weak copies onto empty sheets. I have
recipies of how to make the jelly-like substance - it was in boys' magazines.

>
> The mimeograph ............................ ok until:

Thousands
> of copies can be made if you are careful not to wrinkle or tear the
> stencil because you can re-ink the cotton backing from behind.

----- actually the re-inking is from the back all the time, through the
stencil.

If you
> accidentally get ink on the front of the stencil by putting it on
> backwards you have ruined it. The ink comes thru the back.

----- I can add that Gestetner in the UK were great competitors, and that Rex-
Rotary from Denmark (manufacturer Zeuthen & Aagaard) was also quite known in
the 1950s and 60s. In the 1970s they invented a practical scanner, in which
electrical sparks created holes in a continuous, non-woven stencil, dependent
on the reflection from the scanning part. There were two drums on the same
shaft; the scanning drum and the eroding drum. It was very much like old
telephoto, but I think they still got a patent.

>
> The 'ditto' machine used a plain paper where a carbon ink paper is behind
> the paper.

----- the whole point is that it is not carbon ink - it is not pigmented at
all. It is a soluble color, originally aniline-based (the basic purple
colour)

 You write or type on the front of the paper without cutting
> thru it -- use the typewriter ribbon in normal position -- the carbon
> ink gets deposited on the rear of the paper. This stencil is then
> placed on a plain solid metal drum with the inked surface outwards. (If
> you put it on backwards--no harm. Just remove and put it on
> correctly.) There is a container where a clear spirit solvent is
> poured. This spirit fluid slightly dampens the printing paper which
> picks up the ink as it passes thru the machine. Because the PAPER is
> dampened with the spirit solvent, it has that sweet smell for a few
> hours. Only a hundred or so copies can be made before the carbon [NO!; as per above!]
ink on
> the stencil gets used up. While most of the carbon ink sheets are
> purple, there were about five or ten different colors available, and you
> can switch these carbon sheets and make a multi-colored stencil. (You
> have to use different machines with different stencils if you want to
> have multi-colored mimeograph copies. A separate stencil for each
> color, and usually a different machine because it takes a half hour to
> completely clean a machine!)
>

----- double-sided printing was not possible with the spirit duplicator, but
certainly with the proper stencil one.

Kind regards,


George