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z-man
07-08-2007, 05:23 AM
The wire wrapped rod is available from several sources. I no longer have the URL handy but one company is in Rochester, (Webster to be specific). It works well, but is messy.

The curtain method is good and also messy. I have seen several methods for coating plates. I show one of them in the slide show on making and coating posted in the sticky here in this forum.

Kodak used what is basically a wier coater with emulsion being deposited on a single large moving plate of glass which was then cut into smaller plates when dry.

The best plate coatings I have seen were done with the teapot method where a puddle of emulsion is poured into the center of the plate and then the plate is rocked to distribute the emulsion evenly over the plate. The excess is poured off from two opposite corners then.

This was a production method used early on before Kodak automated the plate coating process.

PE

very interesting-esp the 'teapot' pour

the pulling of an emulsion with a wire wrapped rod is so much like pulling the ink on a silk screen frame that i was able to learn the "identicolor" way very quickly-it doesn't have to be messy if production speed is not an issue

it would be very easy to build a rocking table along the lines of the coil spring supported masks used by many to dodge or burn on a contact vacume frame-when u put the table in motion during exposure, the hard edges of the masks become soft on the emulsion and you can blend multi layer exposures that way

do you think that such a table would work for puddling and smoothing the emulsion , or was it done an easier/simpler way?

perhaps a pendulum suspension such as that recomended by kodak(eroniously) for producing spreads and shrinks which gave rize to the counterintuitive name "unsharp mask" would work?

by the way, for those who don't know, such masks are produced by controling the distance between the emulsions in a contact frame-emulsion to emulsion exact size dupe, emul up on top of emul up mild spread/shrink, emul up on top of emul down more size difference in spread/shrink

emul up, spacer, emul up totaly controlable and repeatable in thousands of an inch as needed for spread/shrink mask by selection of spacer thknss and time of exposure and choice of diffusion screen (same size as frame) over frame or not

saul bolanyos says that spirit leveling the table for the plates and then pouring a puddle and spreading/smoothing with a gloved finger on 35mm or medium format sizes is good enuf if your emulsion is without, or low % , alum hardener

any comments/thoughts?

vaya con dios

Photo Engineer
07-08-2007, 09:47 AM
I don't think that Kodak ever built a rocker table that was as good as a human being doing it by hand. They went directly to the wier type curtain coater.

BTW, I've been told that to prevent frilling it is good to run a file along the edges of the plate before coating to give it some 'tooth' so the emulsion will have a better, rougher surface to cling to. Kind of like a small bevel that is frosted....

PE

z-man
07-08-2007, 02:02 PM
I don't think that Kodak ever built a rocker table that was as good as a human being doing it by hand. They went directly to the wier type curtain coater.

BTW, I've been told that to prevent frilling it is good to run a file along the edges of the plate before coating to give it some 'tooth' so the emulsion will have a better, rougher surface to cling to. Kind of like a small bevel that is frosted....

PE

pe-whats a wier type curtain coater?

the co in rochester that still makes/sells wire wrapped rods-what are listed under? press room/ prep supplies? darkroom ?

that rec re frilling makes me think that the idea of using the textured non-glare glass as a suport may be a good one-still can't find a local source for that glass

there used to be a kit u could get in craft shops for fast and easy 'ground glass' that was a spray can of some kind of etchant and it was low leval re toxicity -surface produced was alomst opaque tho so i moved on

any experience with optically clear rigid plastic as a support?-sheet acrlyc? lexan is available in .010" at home cheapo-i have located sources for gelatine precoated celulose acetate and mylar but they are non rigid and film base size- .005

the uv transparency of plastics versus glass is very attractive to me-i have had to move back to glass for my eye prescriptions for the uv blockng factor

i am convinced that the float glass -crown glass issues in old glass plates and the dif in uv blocking is important-the uv component in light sources and the various results depending on the mix of uv and visible-using open shade to gain contrast in the old sun powered production lines -is well documented

do you know if kodak used a special glass for the frames .back in the day ,that they put on the roof to spit out the prints? the 'green houses' that were sometimes special built for the contact printing production lines-special glass or was it what ever the contractor sourced and chosen by cost considerations?

old production methods are often not easy to duplicate because the commonly used off the shelf products used as components are no longer made or are a differnt thing entires
ly

time changes the name and not the composition or the ingrediants and not the name in my experience

vaya con dios

Photo Engineer
07-08-2007, 03:28 PM
I know little to nothing about the details of Kodak plate making. It ceased ages before I joined the company.

The wier type curtain coater was basically a slanted metal plate with a trough at the bottom. It was held a few mm above the moving plates and was heated with water. Emulsion cascaded down the slanted plate and filled the trough and then spilled over the edge in a cascade like a waterfall. This gave it the name curtain coater.

This is used today to produce high speed color coatings with many layers at one time. However, the design of the machine is different.

The URL with direction to the wire wrapped rods is somewhere on APUG. I have little interest in them due to the mess you make using them and the high consumption of emulsion making a coating.

I want to do things as cleanly and as inexpensively as possible.

PE

ben-s
07-08-2007, 07:49 PM
The URL with direction to the wire wrapped rods is somewhere on APUG. I have little interest in them due to the mess you make using them and the high consumption of emulsion making a coating.

I want to do things as cleanly and as inexpensively as possible.

I wouldn't want to try wire wrapped rods now that I've experienced blade coating.
My blade was very much cobbled together, but extrapolating the results I got out to PE's properly made blades, I would suggest that they are probably the cleanest and most efficient method of homebrew coating.
They are very controllable as regards coating thickness, and the emulsion doesn't go everywhere when you use them, as I imagine it would with a wire wrapped rod.

Hologram
07-09-2007, 04:08 AM
[QUOTE=Hologram;489323]

these links are what i have been looking for-many thanks

hologram-have you done any of this or similar?

Yes, but for holography only.
In that case one problem was finding/producing a gelatin layer that wasn't too hard nor too soft. The hardness has a strong influence on diffusion speed of the sensitizing solutions. Sometimes it becomes difficult to achieve consistent results. Bath concentration, temperature, dwelling time may have a strong influence on grain size.
And as for using fixed out photographic/lithographic emulsions, this may add lots of noise. It looks though gelatin layers get marked by the removal of AgX grains. I guess you'd be better off using very fine grain emulsions when doing this.

z-man
07-09-2007, 07:31 AM
[QUOTE=z-man;489403]

Yes, but for holography only.
In that case one problem was finding/producing a gelatin layer that wasn't too hard nor too soft. The hardness has a strong influence on diffusion speed of the sensitizing solutions. Sometimes it becomes difficult to achieve consistent results. Bath concentration, temperature, dwelling time may have a strong influence on grain size.
And as for using fixed out photographic/lithographic emulsions, this may add lots of noise. It looks though gelatin layers get marked by the removal of AgX grains. I guess you'd be better off using very fine grain emulsions when doing this.

H-

it seems to me that since holography has stricter requierments than those of 'art' photography anything you are doing is usable by those of us that are here for photography in its more commonly understood sense

are there any links you could provide that would show me the common working methods of home brew holographers?-

i mean in terms of 'plate' making---

ex: i have found out about a material in common use in the art world now--it called "multi media art board" and is made out of paper pulp and thermal set epoxy and it is translucent-

when i get some i will know if it is of any use --it is described as acid free and impermiable to water and "it does not buckle"

i am intending to use it as a support for images but it may prove useful for other applictns

pe's description above of the curtain coater will allow me to develope a modification of my present methods

it seems to me that if a find a support that is pre-coated gelatine-nothing else since the gel is for sizing so that paints/whatever get a good grip on the support, in a factory production line, it will be more uniform than anything i can produce-

re pe's contribution, re kodak production of photo plates by hand coating--these plates would be more uniform than my efforts, since, if you are hand-coating every day to meet production needs re big nos, you will get very good at hand coating

it may be that if i then over-coat with sensitzing solutions , these 'virgin' gelatine layers will, by obsorbsion, give me an emulsion that will be less varible in its characteristics , and i will find out when i do it

as you have pointed out, the gel itself thru it's physical characteristics , has a great influence on the final emulsion's spectral character--

if i can eliminate variables in any way i will gain since the variables in any of these emulsion issues make for a system that is so loose and sloppy that you can get lost trying to tack any one of them down so that you can finese the others into a tight predictable sytem, so that when you feed it an input, you can have a good idea of what it will give you as out-put

i have mentioned the old trick of fixing out a piece of projection print paper as an example

this is no longer necessary-you can get ink jet paper wiht a gel layer and many other characteristics that couild be used as a support for sensitizing with 'alt' process solutions

the use of of-the-shelf products intended for other use, in the manufacture of many things, is an old and still used way of getting uniformity in your own product

thank you for taking me around this corner-i do not yet know the neighborhood

vaya con dios

Hologram
07-10-2007, 07:50 AM
[QUOTE=Hologram;489900]
are there any links you could provide that would show me the common working methods of home brew holographers?-

i mean in terms of 'plate' making---


You'd have to search on www.holographyforum.org

Photo Engineer
07-10-2007, 10:34 AM
The process of sensitizing plates by imbibition or overcoating with dye is well known and can be found in a number of publications from the early part of the last century.

The problems with uniformity led to its abandonment in favor of the current methods.

PE

z-man
07-11-2007, 03:36 AM
The process of sensitizing plates by imbibition or overcoating with dye is well known and can be found in a number of publications from the early part of the last century.

The problems with uniformity led to its abandonment in favor of the current methods.

PE

the problem with stroke induced selective memory loss led to the abandoned flavor of currants in meat pies. . . . .what was i saying?

pe-could you voluntier the general area of research so i can find these publications---when the bookstore " a photographers place " was still on green street in soho i built up a good library of late 1800's and early 1900's methods--my library went with every thing else when a 6 mo hospital stay led to the looting of my old apt-life in the big city. . .

was the repeatablity issue coming from the gel layer, or the brushing on method or the silver/whatever solution?

i think that if i can get a mass produced gel sized/subed/coated support then i have a known constant-the silver salt emul you psoted could be adapted as a 'sensitizer' or regular 'salted paper' solutions could be used

i have been given a formula for subing glass with chrome alum hardened food grade gel
so that the lite-sens gel doesn ot need hardener you then seal it with hardened food grade gel-when i can do it i will post

if i order "prepared" acetate --gelatine coated mylar-- and overcoat with ag/salt this will make film so--

i will laminate to a rigid support and have a 'plate'

the holo crew coat by spinning---i can get a kids paint spinner--any thorghts/;experience witdh spinning coatings?

how did kodak cut the large plate without lifting the emulsion at the cuts?

(why does a 1 or 2 stop over exp of a plain agno/salt emulsion go sepia?)

if i prepare a clean plate and then draw on it with photo opaque wax china marker the emulsion wont stick to marker when i caot plate so that when the plate is developed only image area will be in areas not opaqued with wax crayon and i expect that if emulsin is not hardened it will 'wash off' in the deveoper -if emulsion has alum hardener in it i may be able to transfer the emulsion over the wax marker to another plate and use that to 'print' a whatever on the prints made with the plate

this will produce a certain 'je ne se qua'--wala

vaya con dios

Photo Engineer
07-11-2007, 12:45 PM
Kodak cut or scribed the emulsion surface before cutting the glass. IDK the details.

My references are Wall and also Baker on early emulsions up to the 40s.

Brushing introduced brush strokes, but imbibition of sensitizing dyes introduced other problmes of uniformity as the adsorption was not optimum in salted gelatin coatings. Again, I don't remember details as I never worked in this area.

PE

z-man
07-12-2007, 03:05 AM
Kodak cut or scribed the emulsion surface before cutting the glass. IDK the details.

My references are Wall and also Baker on early emulsions up to the 40s.

Brushing introduced brush strokes, but imbibition of sensitizing dyes introduced other problmes of uniformity as the adsorption was not optimum in salted gelatin coatings. Again, I don't remember details as I never worked in this area.

PE

pe-thanx

vaya con dios

knoxissimpler
01-29-2008, 10:07 PM
Ok, here is a repost of the formula copied from the other post here:
-------------------------------------------------------------------
To 90 grams of distilled water, add 5 grams of photo grade gelatin and bring it to 40 deg C. Stir constantly. When dissolved and there are no floaters of gelatin, add 3.51 grams of reagent grade Sodium Chloride (NaCl). (I find dissolving the gelatin first is best)


wait, should this be 90 ml of water, or are you just switching off between ml and grams? (if so, is the next one that the silver nitrate is in in grams or ml?)

rknewcomb
01-29-2008, 10:47 PM
I am so happy to see all this great information pop back up in a thread! I have tried a little bit to do this, but very much want to make my own emulsion for home brew glass plates. Couldn't be happier if I tried. Add big smile here!
thank you!
Robert N.

Photo Engineer
01-29-2008, 11:43 PM
wait, should this be 90 ml of water, or are you just switching off between ml and grams? (if so, is the next one that the silver nitrate is in in grams or ml?)

All measures are in grams.

PE

knoxissimpler
01-30-2008, 10:16 PM
thank you, but just curious (as I am a newb to the mixing of photo chemicals) is the water in developer, stop and fixer also measured in grams? or is that just a personal preference

Photo Engineer
01-31-2008, 09:34 AM
Water and indeed gelatin, silver and almost all chemistry involved in emulsion making is done in weight/weight units due to ease of workup in the dark and viscosity issues. Processing solutions can be done vol/wt or vol/vol units. However, remember that viscous concentrates such as HC110, measured in volume must be carefully measured. You must rinse out the measuring container of the syrup. You can leave a lot behind in a measuring cylinder or cup.

This is why, in emulsion making, where gelatin is so viscous, that we use weight measurements. When you get the right weight, you have it 'all'. Also, reading a graduate cylinder or syringe in the dark, especially with emulsion, is very very difficult.

PE

knoxissimpler
01-31-2008, 06:41 PM
thank you ^_^

knoxissimpler
02-20-2008, 09:25 PM
sorta in a bind, I made the emulsion (finally got it approved), but tomorrow is the only time for another two weeks that I can use the darkroom... problem is, if the gelatin is solidified, besides using a hot plate, how can I melt it to apply it to the paper/ other material? I thought about using a copper coil with hot water running through it, but will the copper react with the silver chloride (I KNOW it will with any excess silver nitrate, but I do not believe that will be enough to cause major issues)... I do not know what to do, if someone could please post soon...

P.S.: the container I ended up using (since my other one broke) is unfortunately, plastic...

Photo Engineer
02-20-2008, 10:05 PM
I weigh out the emulsion I need and it can go into a plastic, glass or Stainless container. Then I put it in a tray of water at 110 deg F and melt it. Then I add finals and coat the emulsion. Finals include hardener and surfactant.

PE