Coating technology

[Photo Engineer]

Well, while I'm on a roll, here is another.

Coating technology first started with what amounts to an offset roller that picked up emulsion from a tank or well, and rolled it onto the film or paper. It could only coat at about 10 ft / min and was subject to lots of defects.

Drying was achieved by means of draping the film or paper on wooden slats suspended from the ceiling and these slats introduced defects in the coating that were spaced at 2x the ceiling height. Therefore, a 50 ft ceiling allowed about a 100 ft max coating length with minimum defects due to the buckle or curvature introduced by the wood slats that held the paper or film.

The next method involved addition of a blade that scraped off the excess emulsion making for better uniformity. The blade was either a metal knife or an air knife.

These methods were limited to coating speeds of 10 - 100 ft / min, preferrably the lower limit.

These methods are no longer used except by one or two isolated plants that are of the older design.

PE

 

[pelerin]

Hey PE,
I'll bite... a few questions: does "one or two isolated plants that are of the older design" describe fotokemika and forte, do you have any idea about the cost to assemble and through-put of the coating setup developed by Jim Browning?
Celac.

Well, while I'm on a roll, here is another.

Coating technology first started with what amounts to an offset roller that picked up emulsion from a tank or well, and rolled it onto the film or paper. It could only coat at about 10 ft / min and was subject to lots of defects.

Drying was achieved by means of draping the film or paper on wooden slats suspended from the ceiling and these slats introduced defects in the coating that were spaced at 2x the ceiling height. Therefore, a 50 ft ceiling allowed about a 100 ft max coating length with minimum defects due to the buckle or curvature introduced by the wood slats that held the paper or film.

The next method involved addition of a blade that scraped off the excess emulsion making for better uniformity. The blade was either a metal knife or an air knife.

These methods were limited to coating speeds of 10 - 100 ft / min, preferrably the lower limit.

These methods are no longer used except by one or two isolated plants that are of the older design.

PE

 

[Photo Engineer]

I would rather not comment.

PE

 

[donbga]

Well, while I'm on a roll, here is another.

Coating technology first started with what amounts to an offset roller that picked up emulsion from a tank or well, and rolled it onto the film or paper. It could only coat at about 10 ft / min and was subject to lots of defects.

Drying was achieved by means of draping the film or paper on wooden slats suspended from the ceiling and these slats introduced defects in the coating that were spaced at 2x the ceiling height. Therefore, a 50 ft ceiling allowed about a 100 ft max coating length with minimum defects due to the buckle or curvature introduced by the wood slats that held the paper or film.

The next method involved addition of a blade that scraped off the excess emulsion making for better uniformity. The blade was either a metal knife or an air knife.

These methods were limited to coating speeds of 10 - 100 ft / min, preferrably the lower limit.

These methods are no longer used except by one or two isolated plants that are of the older design.

PE

PE,

You know you should consider writing an article for Emulsion magazine. The subject seems apropos.

Whatca think?

 

[Aggie]

PE,

You know you should consider writing an article for Emulsion magazine. The subject seems apropos.

Whatca think?

How about a series? Yes Ron I will be calling, I just got hung up with the last couple of weeks of the Shakespearan Festival.

 

[pelerin]

I would rather not comment.

PE

Gosh,
Sorry if that was the wrong question. It just seemed to me that a partially automated coater such as Bronwing describes might be the perfect tool with which to answer small volume demands, e.g., specialty fiber papers and ULF film. (If it were not cost prohibitive) I imagine it would be possible to form a coop to bring such an idea to fruition.
Celac.

 

[Photo Engineer]

Gosh,
Sorry if that was the wrong question. It just seemed to me that a partially automated coater such as Bronwing describes might be the perfect tool with which to answer small volume demands, e.g., specialty fiber papers and ULF film. (If it were not cost prohibitive) I imagine it would be possible to form a coop to bring such an idea to fruition.
Celac.

Sorry, but my post referred to both questions you asked, but if you want a more specific answer, here it is.

Jim Browning has two coating machines. Either of these is a small volume coating setup that is roughly equivalent to hand coating in some ways in that it is limited in scope but can produce high quality coatings. Either of these would probably be capable of supplying a low volume market.

Not having seen either in operation, I can't comment further.

PE

 

[Terence]

Being a curious engineer and wondering what an air knife was, I came across the following link: http://www.wisegeek.com/what-is-an-air-knife.htm

But I'm not sure how it would be used to remove the excess emulsion. Does it just push down and even out the emulsion, or would it actually blow a part (layer?) of the emulsion off the substrate? If the latter, how do you keep it from blowing ALL of the emulsion off? Angle? Pressure?

 

[Photo Engineer]

Thanks for the reference.

It evens out the emulsion layer by forcing it to flow downward just like a doctor blade does. A doctor blade is an actual metal bar that is a precise distance away from the moving emulsion layer and support and removes excess wet emulsion while it is still hot and mobile.

The air kinfe does the same thing, but has no contact with the emulsion layer itself. The air knife was not used by EK (AFAIK) but a lot of other companies did. Kodak used the doctor blade. There was quite a bit of difference of opinion regarding which method was best. IDK if it was ever settled, but both had advantages and disadvantages.

The excess emulsion either filled in uneven areas in the coating or it actually scraped the hot, wet emulsion back into the reservoir.

PE