Re: Gravure tissue

From: Craig Zammiello ^lt;zamm@optonline.net>
Date: 03/07/04-08:00:24 PM Z
Message-id: <004801c404b1$1e99e0a0$0200a8c0@Downstairs>

Richard and Jack,

I'll try and answer some of the questions regarding tissue.

> Do you prefer the burnt sienna color? Does the color matter at all?

Actually, I think a lighter pigment would be ideal as long as it is in the
"red" area.

The pigment is used to provide a visible image to gauge exposure after
developing washout, and for visual tracking while etching the plate. It is
also used to limit the diffusion of light within the gelatin layer during
exposure. That is why the pigments all tend to be reddish to reddish brown.

Also, the "speed" or "contrast" of a particular tissue can be controlled by
the amount and type of pigment present. In general, the higher the pigment
content, the lower the contrast/speed of the tissue. To a lesser extent, the
type of gelatin will also determine contrast/speed.

I recall that Hansfstengl had a series of "synthetic" pigment papers which
were supposed to be superior for etching. They employed dyes instead of
actual pigments. I never tried this product and it was discontinued before
the actual shutdown of the company.

> I am making the carbon with 250 Bloom gel which is pretty high. Would that
> be a benefit? You seem to say it is?
> Would a thicker tissue be of a benefit? Again that is implied in your
> comments?

This is a hard one to call. The maximum thickness of a gelatin coating
should not exceed about 8 microns during etching, which represents the limit
of thickness that can be penetrated under common etching conditions. I guess
in practice, the thickness range of gelatin on a paper substrate is very
small. I use Autotype G25 most of the time, and it is 42, (a symbol which I
think stands for microns).

> Haenfstengl was about 2.4 mil as I measured some once. >

I think that would be a great jumping off point for the thickness of the
coating. I mean, they had a pretty dependable product. When I refer to
Autotype tissue as being "thin", I might be using the wrong term. It's more
of a feeling of a "thin" resist. This might have a lot more to do with the
chemistry of their carbon tissue then the actual thickness.

> Ashless gelatin was used in making tissue for ceramic processes so I am
not
> sure why Autotype is using that. I could make ashless gelatin but it is a
> pain and would run the cost up.

 Autotype's gelatin makeup is quite strange to say the least. They claim to
use "a blend of gelatins" for their G35 tissue (normal contrast) to deliver
high sensitivity at low light intensities. Also, the additives which are
inserted in the coatings must play a role on how it performs too. Things
such as soaps, sugars and glycerin are added in propriety formulas to
control pliability, act as preservatives and modify the working qualities of
the tissue. Who knows what they are currently adding in theirs...

Another problem with Autotype could be the actual ph of the gelatin they
use, which has an effect on speed. I don't know what "ashless" gelatin is,
so I'm not at liberty to make a comment on this, except that you would want
to have as neutral a ph reading as possible in the gelatin. Ph also comes
into play in the dichromate bath, having another effect on tissue speed, so
why compound it with an out of kilter ph to begin with.

 As for bloom, I would stick to a gelatin of medium hardness, as this is
what is most mentioned in the old texts and what not.

> I assume that most plates need extensive retouch work before printing

Not true, if you're doing the job right. Having the proper density range in
a positive is can solve 75% of problems in the outcome of a successful
photogravure print. So, ideally, there is no retouching needed in the
finished plate. Of course, the etching in multiple baths and determining the
time in each is also a deciding component in whether one has to do any
retouching to the plate. But with the proper positive and a set regimen of
times, temps and baths for etching, no retouching should be necessary.

This is not the case with what is known as "direct gravure" where one uses a
drawing or painting on frosted Mylar or grained glass. If the highlights of
the image are close to the base density of the Mylar or other substrate,
then retouching in the form of selective polishing will be necessary. But a
photo should come out looking just the way you want it from sink to the
press.

The biggest problem with Autotype that I have found is accurate control over
the final stages of etching the highlights. It can be quite unpredictable in
the lower baths of 40 and 39 baume. This was not the case with McGraw
Colorgraph or Hansfstengl tissue.

I don't think the differences in having tissues with varying characteristics
would be much of a problem with most folks doing gravure. As with any
Alt.Photo process, you break out the Stouffer scale and do a bit of
homework. It would be worth it in the end to have some choices for different
applications. I use G25 tissue sensitized in a 5% dichromate for screened,
halftone and line/type work. For con-tone grain aquatint applications I
switch to G35 sensitized in a 3.5% dichromate solution. There are different
exposure times, etching times and even single bath (line and type work) as
opposed to multiple baths (45 to 38 baume, 6 baths) for con-tone aquatints.
It's all relative...

Something else I failed to mention for those gravurists plagued by "devils":

During sensitization of the tissue, minute amounts of material will dissolve
from the surface of the gelatin and become suspended in the sensitizing
solution. This becomes evident after repeated usage by the discoloration
(turning brown) and sediment at the bottom of the container of dichromate.
This particulate matter can be carried over when ferrotyping and become
embedded in the surface of the carbon tissue, resulting in minute holes when
developing which in turn become "devils" while etching.

So always filter your dichromate after usage. A drip coffee filter in the
funnel works quite well.

I hope we can get this up to speed. Just the thought that you are
entertaining the actual production of a new carbon tissue is enough to keep
me awake at night! :)

I would love to speak to some colleagues about this and try to glean some
further info that could be of benefit for you Richard.

Will be in touch shortly with any info I can dig up.

My best, Craig Zammiello

> At 07:14 AM 3/7/2004, you wrote:
> >Richard,
> >It's very exciting that you would consider making a carbon tissue for
> >gravure usage.
> >I don't think you would cut into Auto monopoly to the extent that they
would
> >cease making their product, as it has a very healthy, if small, consumer
> >base in Europe.
> >
> >The problem that has been brought up about Autotype's tissue, referred to
as
> >assh*les, is in my opinion, not a fault of Autotype's manufacturing, but
> >created during the actual process of making a gravure plate, or to a
lesser
> >degree, during the sensitizing of the tissue. What people may be seeing
> >could be air bells trapped during the ferrotyping of the tissue. Not to
be
> >confused with trapping air during laydown on the copper which results in
> >visual air tracks (bubbles) in the stencil. These actually don't etch,
and
> >result in white spots on the final print.
> >But, trapping small amounts of air during ferrotyping create areas of
> >thinner gelatin, especially with Autotype tissue, due to it's low gelatin
> >bloom. These thinner areas will etch quicker and finally blow out to form
a
> >"devil".
> >
> >The "star" like gunshot wounds to the plate viewed after etching were
> >commonly referred to as "devils" in the Rotogravure industry. They are
> >almost always prevalent in the shadow areas of the image because those
are
> >etched the longest and this is where the tissue is thinnest. Also, they
are
> >more of a problem when doing actual grain gravure due to the uneven
surface
> >of the plate due to the aquatint resist.
> >
> >The main reasons they occur are due to:
> >1, dust contamination in the process of adhering the tissue to the plate
> >during laydown.
> >Even the best controlled environment will contain small dust motes which
> >will get between the tissue and plate during laydown, causing a
microscopic
> >hole in the stencil that will start etching as soon as the plate is
immersed
> >in ferric. This continues for the entire duration of etching resulting in
a
> >creve-like hole.
> >
> >2. "free" acid contamination of the ferric chloride etching solutions.
> >This is probably a more prevalent problem facing people doing gravure
work
> >today. The free acid will increase the rate of penetration by softening
the
> >gelatin where it comes in contact, usually at the site of a dust mote,
where
> >the gelatin is thinnest.
> >Hunt Blue label Roto Iron ferric chloride, still made for whatever exists
of
> >the rotogravure industry today, contains a very small amount of "free"
acid,
> >but it is negligible for most of our gravure applications.
> >If you are using a ferric chloride other then Roto Iron, you can be
assured
> >it contains much to much free acid that must be neutralized with a
solution
> >of ferris hydroxide.
> >
> >Both of these problems will at one time or another plague someone doing
> >gravures. I've had a close look at Autotype tissue before sensitizing and
> >have never seen any blowouts in the emulsion, though they may indeed
exist.
> >But I believe the two points stated above are a far more common cause of
> >devils then holes in the tissue from the factory.
> >I base this on 30 years of using many different tissues and having these
> >problems intermittently with all of them.
> >MaGraw Colograph tissue was probably the best controlled and finest
tissue
> >ever produced for photogravure. It went out of business in the mid 80's
and
> >sold it's coating machines and proprietary formulas to the German Carbon
> >tissue makers Hansfstengle Gmbh. Hansftengle continued to manufacture the
> >duplicate MaGraw product into the early 90's, when it was forced to shut
> >it's doors. I purchased 19 rolls of carbon tissue from their last run,
and I
> >can say that the last run they was not particularly consistent in
quality!
> >But, at the time, it was still a better product then Autotype.
> >My main gripe with Autotype's tissue is the gelatin and pigment ( iron
oxide
> >which is probably not as finely ground as one would like, as opposed to
> >MaGraw's burnt sienna). The gelatin itself continues to be dubious, a
much
> >lower bloom then what was used in most pigment papers, hence the
difference
> >in temperature (lower) and shorter time (to control swelling and
absorption
> >of the dichromate) in the sensitizing process. It is slimy, course and
not
> >workable above 53 degrees F besides being notoriously thin.
> >But, at the time being, it is the best pigment paper made for
photogravure
> >by default!
> >Cheers, Craig Z.
> >
> >
> >----- Original Message -----
> >From: "Richard Sullivan" <richsul@earthlink.net>
> >To: <alt-photo-process-l@sask.usask.ca>
> >Sent: Saturday, March 06, 2004 2:37 PM
> >Subject: Re: News from Bostick & Sullivan
> >
> >
> > > Assuming this means gravure tissue, what is the gripe with what
Autotype
> > > produces? Quality? Price? Would folks be willing to re calibrate to a
> > > different tissue. It is my understanding that Autotype dearly wants
out of
> > > making it. The risk is if I come out with it and they drop it, I am in
a
> > > pickle as I have then inherited the mantle. There would be no getting
out.
> > >
> > > I have heard that some batches are plagued with what are in the trade
> > > termed assh*les, tiny areas that cause asterisk looking pits in the
> >copper.
> > > This i got from a couple of gravure printers here in Santa Fe and also
in
> >a
> > > book on gravure from the 30's. I believe they are caused by small
pinhole
> > > bubbles in the tissue. With this long a history it may just be an
endemic
> > > problem in making the tissue.
> > >
> > > Thanks for the comments.
> > >
> > > --Dick
> > >
> > > At 12:07 PM 3/6/2004, you wrote:
> > > >I would like to recommend the production of gravure paper. Autotype
could
> >sure
> > > >use some competition.
> > > >
> > > >Jack Reisland
> > > >
> > > >Richard Sullivan wrote:
> > > >
> > > > >
> > > > > With the coating machine I am looking at other coated products
like
> >oil
> > > > > paper, collotype film, albumen, etc. Comments welcome.
> > >
> > >
> > >
>
>
>
Received on Sun Mar 7 20:00:33 2004

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