The ‘Ditto Machine’.

28 August, 2008. Tagged as Interesting Things.

On the second last day of 11th grade I was cleaning out the Student Support room for one of my teachers. Student Support is probably the room with the most historic value in the school—some of the documents I encountered date back to 1972.

I’m not sure if that means that foolscap paper (!) has sentimental value, or if the room hasn’t been cleaned for thirty-two years.

Among the things I found are two very stylish pieces of paper, one with what looks like computer-printed typing, another with typewritten text. Both pieces of paper are stained with purple ink because they went through a machine invented in 1923 called a ditto machine, or spirit duplicator.

A ditto machine was a primitive photocopier that used a solvent like methylated spirits or ammonia to transfer ink from the master copy (the template, if you will) onto other pieces of paper.

The master copy was a smooth, waxy piece of paper which was thickly inked when printed. The procedure for printing on a master was like the reverse of a carbon-copy; instead of writing on the normal paper and having the carbon underneath, the text and pictures were printed onto carbon paper of varying colours to transfer print to the master. If you want to know exactly how thickly a master was inked, put your printer on the best quality and print about two or three passes onto the same sheet of paper (so that you are printing over the previous printing, I mean).

On a master copy that’s been used, the solvent will have discoloured the area around the print, which I’ll discuss next.

The master was then wrapped around a drum, and the solvent was applied as the drum rotated. The solvent either softened or melted the ink so that just enough of it would stick to the blank sheets of paper. A lot of the copies produced in this way came out with purple ink because purple “provided the best contrast”, but I found it pretty hard to read.

Even when computer-enhanced, purple ink isn’t easy to read.

Ditto machines were commonly used in schools, and the students believed that sniffing the solvent fumes from a freshly copied sheet would provide a high—a reasonable assumption given the instances and effectiveness of substance sniffing. My teacher says that the kids would spend the five minutes after receiving a new sheet just smelling it.

Of course, this is now a dead technology mainly due to the entrance of speedy, efficient photocopiers like the Xerox machine in the 1970s and the laser printer in 1975, which in time would be capable of effortlessly printing on literal globs of dead tree.

Still, it’s nice to remember our roots and the technologies that we used to get where we are. It is mind-boggling to think of all the millenia of human evolution and cooperation that were necessary to produce something like a ditto machine. If you’re in an existential or pro-humanity mood you could even say that all our efforts have been geared towards the production of such a technology, before we decided that we could do much better.




Julie asked, Do you know if the carbon paper used in a ditto machine is still available? I am trying to locate some for an art project.

I said, Believe it or not, tattoo artists still use spirit master sheets. They draw or trace the design of a tattoo onto the top layer and then use lube or a solvent to transfer the inked design from the paper to the skin. Ask your local tattoo artist.

Failing that, Superior Tattoo sells some, though I am not quite sure if you will have to buy a pack of 100 to get them in any decent size. I also found an auction on the American eBay for a pack of old Thermofax sheets. Search for thermal paper, or tattoo paper, or Thermofax.




Lola said, as you probably already know, your ditto machine post made it onto the amc blog for mad men - very nice.
about that post - i think xerox machines broke into the office in a significant way in 1962.

I said, Thanks for the extra information about Xerox machines. The date I had, the early 1970s, is when Xerox introduced their first color copier. You are indeed right when you say that it was around for a fair bit before that!