Dry Plate Coating

[argentum_et_lux]

I know glass plates are so last century . However, since seeing my first glass plate I have never been able to move on from this method and so have sunk way too much time into it.

The last year or so I have been building a dryplate coating machine that at this point is at about 95% success rate of plates coated. I am in the process of making some design changes and having the parts manufactured to increase its precision. I am not ready to post photos of the machine or plates until I decide what its future will be.

Simple coating machine description: Plate is inserted in a very precisely machined fixture with vacuum table underneath that secures the plate. The fixture is heated by a computer controlled system that keeps plate at ideal temps for coating. The plate is then moved under a precise dispenser that drops close to the exact amount of emulsion required(a little extra is used do to losses). The plate is then spun up to evenly coat the plate. The plate then moves forward and is finished by a precisely milled coater that is height referenced to the plate to ensure a perfect coating thickness. The plate then is pushed out of holder into a drying chamber that has he-pa filtering to keep them clean.

I am looking to do tintypes as well but will need to mod the fixture to hold the metal plates more flat. I can get glass that is quite consistent as far as being flat but metal is still an issue.

I guess my question is do you think if I get this perfected that there is any market for small runs of dry plates? I am in talks with a couple of suppliers about making a run of custom emulsion for this project as my emulsion leaves something to be desired at this point. I don't know if I will make this a kit to build your own machine, open source project or try to sell small runs of plates. Just thought I would see what everyone here thinks about it. When I have decided what path this project should take I will post more detail of the machine, how it works, and the results.

 

[Peter Schrager]

Yes and yes...I'll try some!!

 

[removed account4]

fun project!

sounds pricy though

 

[Photo Engineer]

Mark Osterman has posted photos of the Kodak dry plate coater. You might be interested in them on his Facebook page or on the George Eastman Museum site. There are several others going in the direction of coating plates.

PE

 

[removed account4]

hi PE
i've searched the GEM site and facebook pages, ( as much as i can see without being a FB customer )
and unfortunately i can't find the images you are refering to. if it wouldn't be too much trouble
can you post a link ?
thanks!
john

 

[Photo Engineer]

Coating wier on Mark's Facebook page for April 6th. Much more including machine diagram.

Nick has posted recent pictures of their coating machine as well.

Dead Link Removed

PE

 

[removed account4]

thanks !

 

[argentum_et_lux]

Here are a few issues that i am not sure yet are issues:
The coating extends quite evenly across the entire plate. But when I look at for example kodak dry plates the emulsion does not go to the edges. Will having the coating go to the edge make it more prone to lifting over time. Not seeing it right now but what about in 5 or 10 years or more?

I have thought about using stainless laser cut templates from pcb industry that would keep the edge around the plate clear. Have not tried it yet but would the stencil have to be pulled when still hot or when plate cools to avoid damaging the emulsion?

Should I precoat the plates with a spray coating of gelatin and alum to make them more durable? I think I could use a spray process for this but not sure how important it is for longevity.

Spin coating is great but to make a balanced jig that is perfectly level and spinning is not cheap or easy for diy so still thinking about other methods. Ultimately, my goal is to make glass slides easily available again for the DIYer.
I intend to make a machine that anyone can copy and understand with reasonable effort.

Anyone have diagrams or pictures of Eastman's early machines? I have not really been able to find anything descriptive or showing detail

 

[Photo Engineer]

Look at the reference I gave. Mark has put up a diagram of the coating machine.

As for lifting, plate edges were often beveled and roughened to give the emulsion something to grip, but we have not seen this in coatings at GEM. And, there is no undercoat used. The trick is to give plates a good cleaning.

PE

 

[Prof_Pixel]

Anyone have diagrams or pictures of Eastman's early machines? I have not really been able to find anything descriptive or showing detail

Try Googling eastman dry plate coating machine diagram

 

[Nodda Duma]

Look at the reference I gave. Mark has put up a diagram of the coating machine.

As for lifting, plate edges were often beveled and roughened to give the emulsion something to grip, but we have not seen this in coatings at GEM. And, there is no undercoat used. The trick is to give plates a good cleaning.

PE

Not that it needs to be done, but I wanted to reiterate what Ron says about edging. I'm using hand-cut 4"x5" glass plates with no special treatment of the edges (no bevels or grinding), and do not apply a sub layer. I have no issues with emulsion lifting so long as I thoroughly clean the glass. I use a mix of dish soap, rottenstone, and water which is effective at removing the cutting oil.

Also for reference, I just coated 80 plates last night and recorded emulsion use to be 0.25 ml / square inch. I divided total volume of emulsion by total area coated, and digging around the internet tells me that's probably typical.

 

[brazile]

I'll echo Jason, and will add that Mark has suggested that the cutting oil isn't necessary, that the cutter seems to work fine and last quite a long time without it. In the workshop, they cut the plates without oil, and have the participants just use dish soap to (thoroughly!) clean the plates. Using your hands to do the cleaning takes off sufficient oil from your hands that it tends not to leave any on the plates, although Madge might not approve.

No promises, but I've been following Mark's suggestion and cutting mine without the cutting oil and have had no obvious issues, and haven't had to deal with removing the oil. When reusing plates (i.e., cleaning off old emulsions with dilute bleach) I do occasionally use a bit of whiting to make sure I haven't left anything behind, as once or twice I've had a plate reject the emulsion in spots, presumably from a bit of old stuff left on the plate. That has not happened since I started using whiting.

Robert