Re: Gravure tissue

Sandy,

I have the book. Great book too.

Thanks

--Dick

At 07:31 PM 3/7/2004, you wrote:
>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 42µ, (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 Mon Mar 8 12:16:22 2004