Photographs of the coating blade

[Jerevan]

A thousand words have been written about its design, but I wonder if there is anywhere I can see good photographs (or a sketch) of the coating blade that has been constructed by Ron (and now sells at Photoformulary)?

I found some photos at Photoformulary but they aren't very informative. Buying something for $550 plus shipping and taxes needs a bit more than this. Has anybody bought it yet, or is there anyone who will be making a review of it?

 

[Photo Engineer]

I have posted several pictures of one here. I'll try to take a pic of one today and post it. It will be digital, but Sean thought that was the ultimate thumbing of the nose to digital. Take a digital picture of a new piece of analog equipment.

The pictures I have are not good. The blades are very shiny and reflect light. I'm going to have to photograph a prototype which was not polished.

About 1/4th of the original production run was sold. Denise Ross has said that she would try to post some comments on them. She plans on buying her second one. I have several special orders from people who have used them or bought them. Two of them are in production right now.

George Eastman House was the first customer. They know how these blades are used at Kodak and RIT.

PE

 

[Jerevan]

Thanks PE,

it's good to know the product sells and the interest in it seems genuine! I am really interested in reading any real world experience comments or reviews. At the moment the blade is out of budget for my experiments but I am definitely am going to keep an eye on future developments. Thank you for your efforts.

Jimi

EDIT: Isn't it strange? I have been looking high and low, but right after I posted this reply, I found some of the photos you had posted earlier - I did a search for photographs of coating blades - and found this thread: (there was a url link here which no longer exists)

 

[Photo Engineer]

Photos of coating blades

Here are 2 photos (actually a composite of 4) taken with a digital camera of a new device for making analog photos.

The first picture is one production run of 20 paper coating blades, consisting of 10 8x10 blades and 10 4x5 blades. At the left side of the picture is a prototype 11x14 blade. A pen is included for scale.

The picture also includes a picture of the items you will need for maintenance which are a feeler gauge and an allen wrench. They are on the right in the first picture. At the top of the first picture are several prototype film blades.

In the second picture, you see front and back pictures of a film coating blade. The adjustment screws are clearly seen, as are the openings for the allen wrench.

Hope this helps.

PE

 

[Jerevan]

Now that I look at these photographs, I understand better how the blade works. I was wondering how it was possible to gauge the distances given in earlier threads, but hey, feeler gauges... sometimes things don't need to be complicated, eh?

 

[Photo Engineer]

If you want easy, and don't want to mess with feeler gauges, then here is something to remember.

35 mm film is 5 mils thick. (0.005")
120 film or 220 film is 2 mils thick.
4x5 or any sheet film is 7 mils thick.

So, I actually use pieces of film for quick calibration. The error introduced by the coating on the suppor is so tiny it is not worth mentioning.

PE

 

[Terence]

As an engineer I'm feeling quite ignorant. How are these blades used. In the left photos, I see a "c"-shaped milled piece of steel with what appears to be a single blade across the mouth of the "c", forming a bow-like instrument. In the photos to the right it looks like a single blade on the "back" of the "c", leaving the mouth open.

Where does the film-base go? Does it go in between two pieces, or does the blade skim over the film-base?

I must say, I always visualized the blades as more squeegee-like. I saw the previous thread, but must have stopped reading it before the last several posts were added.

 

[Sal Santamaura]

...120 film or 220 film is 2 mils thick...

120/220 is typically 4 mils thick; T-MAX is 4.7.

 

[Photo Engineer]

120/220 is typically 4 mils thick; T-MAX is 4.7.

Sal, you are right. It is 4.0. I really slipped up on that one. There is a common household product that is 2 mil. That is what I was thinking of, but I cannot remember what it was.

Thanks for the catch!

PE

 

[Photo Engineer]

As an engineer I'm feeling quite ignorant. How are these blades used. In the left photos, I see a "c"-shaped milled piece of steel with what appears to be a single blade across the mouth of the "c", forming a bow-like instrument. In the photos to the right it looks like a single blade on the "back" of the "c", leaving the mouth open.

Where does the film-base go? Does it go in between two pieces, or does the blade skim over the film-base?

I must say, I always visualized the blades as more squeegee-like. I saw the previous thread, but must have stopped reading it before the last several posts were added.

Terence;

The blades are drawn over the support.

In the case of the paper blade, the open well is filled with emulsion and the leading edge keeps the paper flat. In the case of the film blade, there cannot be a leading edge, as it would scratch the film, so it is open and the emulsion is poured ahead of the blade.

An adjustable doctor blade is the trailing edge in each case and it 'scrapes' off the emulsion to the fixed height that the coater sets the blade for.

This gap is typically 5 mils, but the range is from 2 mils to 20 mils. Often, viscosity must be adjusted for the gap width, and if the gap is large, a dam must be used to prevent premature leaking and side flow.

A chill set block is used often for heavy film coatings, but for FB paper, the paper support will absorb most of the excess moisture and set up nicely.

PE

 

[Terence]

Okay. I think I get it now. Is the bottom of the center portion of the "C" recessed compared to the outstanding legs? I am assuming it is, and that the legs straddle the film/paper base, right?

Assuming the above is correct, why use two screws at each end instead of spreading them out along the blade to give better support? I'm guessing that my conservative nature is coming out and that the blade is stiff enough and the emulsion viscous enough that you don't anticipate much deflection in the blade?

 

[Photo Engineer]

Okay. I think I get it now. Is the bottom of the center portion of the "C" recessed compared to the outstanding legs? I am assuming it is, and that the legs straddle the film/paper base, right?

Assuming the above is correct, why use two screws at each end instead of spreading them out along the blade to give better support? I'm guessing that my conservative nature is coming out and that the blade is stiff enough and the emulsion viscous enough that you don't anticipate much deflection in the blade?

Terence;

The blades you see are sitting on the surface that rides on the support. You have things rotated 90 degrees in your mind. The surface contacting the support is polished mirror bright and is square, and that is part of the price problem. There can be no leaks around the edges or under the flat part. The corners that lead the direction of motion are chamfered to allow smooth movement without catching or grabbing. There are a lot of features not apparent in these photos. These are my 4th generation of blades.

The trailing edge of each blade is the movable plate which is raised up by a varying amound by means of the 4 screws, so when you are looking at the screws you are viewing the trailing edge of the blade.

The emulsion flows under that gap and is held at a constant laydown by that gap.

The 4" blade weights about 1 pound, or about 430 grams, the 8" blade is about twice as heavy. The end cap is heavy enough stainless to prevent any fluctuations. The 8" blade uses a heavier end cap than the 4" blade for just this reason. The weight is high to prevent wobble during coating. It is a high end stainless to prevent corrosion from the chemicals used.

BTW, a similar blade is used in the paint industry to evenly spread paint during tests. These blades are only 4" wide and are made of aluminum. The last time I queried the company these blades were $1200 each. I can no longer locate that web page. I guess they went out of business. At the time though, Kirk Keyes directed me to this additional use of this type of blade. I didn't go with one of these, as aluminum is not compatible with emulsions.

PE

 

[timeUnit]

I just love this thread...

Here I am, trying to get 4x5 developing right, and you are coating your own film... I've got LOTS to learn!

Keep it up!

 

[Ole]

I want one - or two - or three! ...

As soon as I can afford one, which seems to be further and further off.

Maybe I should stop looking for strange old things on ebay? Or perhaps it would be easier and less painful to stop smoking...

 

[timeUnit]

Or perhaps it would be easier and less painful to stop smoking...

Probably as difficult. But definetely more healthy. ;-)

 

[reggie]

<snip>George Eastman House was the first customer</snip>

Is that a retirement home for ex-emulsion engineers?

-R

 

[Photo Engineer]

Is that a retirement home for ex-emulsion engineers?

-R

If you don't know what George Eastman House is ................

Nuff said.

PE

 

[reggie]

If you don't know what George Eastman House is ................

Nuff said.

PE

Hey Ron:

The nurse said to take off the lab coat, put down the computer and come down to supper. You can get back on the computer after I've had my turn.

-R

 

[Photo Engineer]

Well, I did just come out of the darkroom, I hung up my lab coat, and I'm now answering about 2 hours worth of e-mail and adding to posts here, including this one.

Happy?

I would love to retire to GEH. It is a photographers dream home. The darkrooms there are first rate! So is the library.

PE

 

[reggie]

I would love to retire to GEH. It is a photographers dream home. The darkrooms there are first rate! So is the library.
PE

That's all fine, but how do you plan on making it past the silvery gates at GEH?

BTW, please e-mail me or PM me on the state of my 12x20 blade, ok?

Thansk, Ron.

-R

 

[Photo Engineer]

That's all fine, but how do you plan on making it past the silvery gates at GEH?

BTW, please e-mail me or PM me on the state of my 12x20 blade, ok?

Thansk, Ron.

-R

I can answer here. The blade blank is being drilled and tapped, then chamfered, and then polished. I'm waiting to hear from the tool and die works as they have 4 others to do as well. I have 2 more blanks here for them to work on.

PE