Re: "speckling" v "staining "

On Sat, 10 Sep 2005, Katharine Thayer wrote:

> ... But I keep coming back to the same thing: there is, as
> you say, a large set of observations about glyoxal, since it has been
> widely used for 10 or 15 years. If the case can be made, statistically
> speaking, that glyoxal doesn't provide adequate stain resistance, it
> just seems to me we would have heard more about that problem before now.
> I suppose it's possible that people have just been printing stained
> pictures all this time because they were too dumb to know any better,
> but I have more respect for my fellow gum printers than to assume this
> is the case.
> By the same token, if glyoxal and glutaraldehyde were equally dangerous,
> surely we should have been hearing reports of glyoxal reactions over the
> years from some of the many many people who have used it.
> Katharine

>From the very first tests I did with glyoxal, I found it hardened better
than formaldehyde -- and, except for two things, was just about fool
proof:

1. A student noticed that her sized paper yellowed during storage. I'd
never seen that previously. It develops now, however, that rinsing the
the paper after a 5-minute hardening bath prevents most or all yellowing.

2. I've found that glyoxal working solution doesn't keep -- even for a
day (no traces of odor remaining). How long are folks keeping it?

Other than that, I've found it the perfect hardener -- even indoors in
winter weather no sore throat or other bad effects. Equally, if not more
important, I've never seen any connection between speckling or staining
and glyoxal... in fact any speckling or staining I've seen (even by space
cadet undergraduates) has been almost without exception explained by

1. excess heat during sizing
2. drying emulsion by heat
3. unsuitable paper
4. off brand paint or difficult color (eg carbon black)
5. scrubbing during application of emulsion
6. heat and/or humidity while emulsion is drying
7. long wait before development
8. overly aged emulsion

plus, of course some wacked out-gelatin for the size.

Which leads me to suggest,

1. another variable may be the water in other localities which changes the
whole equation

2. perhaps some folks aren't using the glyoxal one-shot?

3. newer papers I haven't used have other variables that give trouble.

4. another thought about speckles -- I do NOT NOT NOT mix paint with gum
and keep in a jar for later use. IME the paint settles at the bottom and
is very difficult to remix smoothly. Maybe it's not well remixed and thus
speckles -- or anyway, IME an accident waiting to happen. Putting in a dab
of paint from the tube is so easy, and much easier to adjust color &
ratios, why complicate things?

Or another possibility -- some folks have a book that says mix your
emulsion with a glass rod. BURN THAT BOOK !!! A glass rod is as bad as a
popsicle stick, worse even. NO WAY to properly mix an emulsion. Use a nice
round BRUSH -- that fear of ferrule stuff is like, um, don't wear patent
leather shoes because the boys can look up your skirt. A myth (AFAIK,
anyway).

But now another possibility occurs to me. I usually vat size, and vat
harden -- that is, dip the paper in a bath long enough to be thoroughly
saturated, then squeegee excess gelatin (illustrated P-F #9), hang to dry,
and bathe the dry paper separately in the glyoxal.

It's entirely possible (note, I do NOT say *probable* though I have my own
thoughts on the matter) that either brush sizing and hardening, or adding
the hardener to the gelatin at the outset is/are less effective/perfect
procedure.

I'll add that glyoxal has, to my knowledge, been "widely used" only since
1998. I tested it according to instructions from Mike Ware, whose graduate
student had done the initial testing. I then published the info in
Post-Factory #1, April 1998, and shortly after that (possibly) to the
list.

Formaldehyde had become so difficult to get in the US (unless you had a
friendly undertaker) and of course glyoxal was so much less painful to
use, it took off very quickly.

Judy
Received on Sat Sep 10 12:56:31 2005