Re: Gravure tissue

From: Sandy King ^lt;sanking@clemson.edu>
Date: 03/07/04-08:31:22 PM Z
Message-id: <a06020415bc7189bc6852@[192.168.1.100]>

BTW, I wanted to mention that I worked closely
with David Morris, author of Copper Plate
Photogravure, in trying to provide a formula that
would duplicate as closely as possible the
Autotype tissue in speed and contrast. David sent
me several large sheets of the material and I
spent about a month calibrating tissue making to
produce a close match of the Autotype material.
See Chapter 11 of the book, "Directions for the
Home Manufacture of Carbon Tissue for
Photogravure Printing." In the end I was able to
get a very close match in terms of contrast,
although the home made tissue was quite a bit
slower.

The gelatin I used was a 250 Bloom ossein
material, of very similar characteristics to the
gelatin that Dick uses to make the B&S carbon
tissue. Since Dick is familiar with my method of
making carbon tissue I suspect that he could take
the formula and with a few tweaks adapt it to his
method of coating.

Sandy King

>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 20:33:12 2004

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