[GreenKeys] [External] Re: History of printing machines

[Jones, Douglas W]

On 8 Mar 2022 at 11:59, Harold Hallikainen via GreenK wrote:

> 4. At one time I tried gelatin printing with a tray of Jello. That did not work very well.

Ah for the days of the hectograph.  My mom had a hectograph.  The "machine" was a stamped tin tray with close fitting lid, only about 1/4 inch deep and big enough to comfortably hold a sheet of typing paper.  It came filled with gelatine.  To use it, you carefully melted the gelatine to erase the previous print run and create a clean new surface.

You typed up or drew your original on something like a ditto master (I think it actually used the same ink chemistry), and then carefully spread the master face down on the gelatine and gently pat it down.  Did you have to pour some alcohol on the back of the master?  I vaguely recall something like that.  Anyway, having transferred the ink to the gelatine, you peeled off the master and gently lay a piece of clean paper on the gelatine and pat it down, then peel it off and repeat for as many copies as you can get before the ink fades to being unreadable.

I used my mom's hectograph to print "The Neighborhood Gossip" some time around 1966, a childhood venture in journalism.  We did our printing on the dining room table, a nice oiled teak table, Scandinavian modern.  The one printing goof I remember was setting a fresh copy face down on the table top and forgetting it for a few minutes.  Oops.  That copy remained slightly legible, in mirror image print on the wood, for a decade or so.

Another forgotten print technology:  Thermofax.  Back before photocopiers were cheap enough for a small department to afford, we had a thermofax copier.  Insert the original, a thermofax master (like carbon paper) and a sheet of typing paper, as a 3-layer sandwich, into the copier.  A roller pinched the sandwich against a rolling lamp.  Black ink on the original got hot enough to melt the ink on the master and transfer it to the typing paper.  White paper on the original didn't get hot enough, so you got a copy.  We used this to make individual copies of typed or handwritten (in dark ink) originals, but it also worked to transfer ditto ink to paper ditto masters that could then be used to make multiple blue (and alcohol-smelling) copies.  Note that Thermofax was not a telefax technology, you were making a facsimilie locally, not transmitting one.

            Doug Jones
            jones at cs.uiowa.edu