Re: PSA Article on Cyanotypes

Judy Seigel (jseigel@panix.com)
Thu, 26 Oct 1995 03:00:43 -0400 (EDT)

> A number of years ago I acquired a small supply of Kodak 2575
> Direct Positive Duplicating Film. This is a continuous tone film of
> moderately high contrast which can be handled under ordinary safelight and

Kodak 2575 has been discontinued for several years......Freestyle sells a
similar (if not the same) as "High Speed Duplicating Film" reasonably
priced. Though no longer in their regular catalog, it's in their graphics
catalog.

A soft-working developer (Selectol soft is also discontinued,
but these can be mixed -- glycin is great) gives adequate continuous tone
with the HSD.

> An alternative is to enlarge a negative on conventional film. If I
> were to do this, I would first contact print the original camera negative
> (35mm or 6x6) to produce a film positive, and then enlarge this to produce
> a large negative. This would be more economical.
>

More economical perhaps, but much more difficult.....at least I found
contacting 35 mm without dust, Newton Rings & scratches no easy task.
There's also the fact that for gum printing a positive is very handy.

> Litho film could be used instead of conventional negative film.
Of > course, litho film has very high contrast and the resulting prints
will > contain onlythe extremes of the tonal scale--bright highlights and
deep shadows. > However, starting with litho film might make sense for

Lith film is widely used with a weak developer to make continuous tone
negatives. (Dektol 1 to 7, to 1 to 15, for instance, though D-76 works
well, & a home-mixed glycin developer may be best of all)

> Later I discovered > spray starch which does
> just as good a job as the boiled variety but with > much less effort. If
> you choose to size your paper, this is the way to go. > > Sizing does two

Spray starch discolors the paper within a very few years. This may not
bother you, but it may also get worse in time.... and suggests other
dangers as well.

> because the "emulsion" is on top of the sizing > and not
in the paper fibers, the unexposed ferric salts in the emulsion can > be
more easily washed out in processing. As a result, unsized prints >
require much more washing and even then the highlights may gradually turn
a > faint blue as the print ages. > > Various references give different

Well, the sizing itself can wash off, and take everything with it. Normal
papers (not very thick & absorbent) wash in 5 to 10 minutes. I suggest 10
to 15 to be safe. Thicker, more absorbent papers take up to half an hour.

> This oxydization process can be enhanced by briefly treating the >
> print in a weak solution of Potassium Dichromate or Hydrogen Peroxide. >
> After all the residual yellow sensitizer has washed out--and that is >

Peroxide speeds the process, but doesn't "enhance" it....

> The bad > news is the
> process can stain clothing and one must be careful to use an > apron
> and/or old clothing when working in the process.

For stains on clothes, "bleach" with a paste of borax or sodium carbonate
(washing soda) or dilute chlorox.

But yes, yes, let's hear it for the color -- cyanotype blue being one of
the great all-star colors of the known world. Do I dare say that whoever
doesn't love cyanotype blue at least a little lacks soul? (Saw some
McDermitt & McGough cyanotypes in slides tonight, impossibly beautiful.)

Judy