From: Patent Tactics, George Brock-Nannestad


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.

> 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:

> 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 

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 

 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,