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

[Bruce Gentry]

We had ThermoFax copiers at my high school and the public library.  They 
could also make transparencies for the then popular overhead 
projectors.  The supplies to make a copy were not cheap for high school 
kids, at 15 cents a copy that was the same as almost $2.00 today. A 
transparency was almost $15.00 in today's money.

     Bruce Gentry, KA2IVY

On 3/8/22 18:37, Jones, Douglas W wrote:
> On 8 Mar 2022 at 11:59, Harold Hallikainen via GreenK wrote:
>
>
> 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
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