Convenient Dry Plate coating table

[Pere Casals]

Here there is an arrangement for a convenient dry plate coating table, that I started using.




The side margins are elevated (trimmed) 0,5mm over the glass plates, the necessary gap to get the desired coating thickness:





Also the side walls (1cm tall) avoid emulsion spill, and the emulsion that's in excess can be recovered at the end of the table.

I use a silicon (cooking) mat under all, as recommended by Denise, basicly it's the arrangement described here:

http://www.thelightfarm.com/Map/DryP...latePart4a.htm

Just I add a side guide that's higher than the plate to trim the emulsion thickness, and I also add the side wall to prevent spill.

I get good results by dropping emulsion pretty hot (55ºC). I also found very useful to previously apply vacuum to emulsion to get rid of any air bubble and then taking emulsion with a syringe.

Emulsion get cold/gelified anyway because there is a thick (1cm) glass under, in some 7min.

Next step is closing the table top with plastic curtains and injecting HEPA filtered air to get rid from dust...

Fell free to add any suggestion...

[dwross]

Very elegant! I love anything that doesn't have to be put together each time you coat. Are the side walls permanently attached? (very nice illustrations, too!)

[Pere Casals]

Very elegant! I love anything that doesn't have to be put together each time you coat. Are the side walls permanently attached? (very nice illustrations, too!)

For the moment I glued all (glass) parts with 3M ReMount spray, this allows to change format configuration.

I've been making test with gelatin coulored with erythrosine (no silver) to see eveness flaws and test it with densitometer, later I also measured dried gelatin thickness with a micrometer, by knowing the total thickness and substracting the glass thickness in each point, after cleaning the plate with hot water... (test points were marked in the other side with a "permament" marker)

It resulted a well uniform coat of about 0.04mm.

I'm considering to make two permanent assemblies one for 8x10 and the other for 5x7 and 5x4.

Anyway a permanent 10" wide table would do all, if placing two 5x4 (or 5x7) plates in each row.

A permanent assembly would have a "not adjustable" 0.5mm trim, this is a limitation, but I consider adding more water to the emulsion in order to result a thinner coat when dried, if necessary.

Another way I consider to adjust (reduce) the coat thickness is placing acrylic (or mylar) sheets under the plates to raise the surface.

Last attempts I made I did not use the silicon mat, I just droped (distilled) water (in excess) on the glass before placing (pressing well) the plates, this avoided the emulsion going under the plates because capilarity (perhaps alcohol may be better).


I found gelified emulsion it is easy to clean with "Ceramic Hob and Window Scraper", or just with very hot water.

Perhaps the non permament assembly allows to protect glasses with food film, so no need to clean it later...

What I can say is that the 3M ReMount spray is very convenient to fix the parts...

I left 4mm from the side walls to the plate edge, this are the lateral guides that trim 0.5mm of wet emulsion over the plate. I dropped all emulsion on the first plate, spreading it to the other plates in a single pass, using a piece of glass (like a comb) that had just 1mm jog from one side to the other.

I used a 10mm glass bed for the table, to have a rigid platform. I also found that droping water (in excess) and pressing well the plates get very "glued" to the bed. This would allow to place two 4x5 plates in a row to fill the 10x8" assembly. A knife like tool has to be used carefully to detach gelified plates from bed... (With the silicon mat it was easier...)

[dwross]

I do use food film with a light misting of water and it pretty much eliminates a big cleanup, but next time I will definitely try using more water on the film! Less emulsion going under the plates would be great. Thank you for the tip. And, also for the idea of using remount spray while you are refining your design.

Don't count on using acrylic sheets to reduce coating thickness. I've never found a piece of acrylic that's as reliably flat as a glass sheet, so it might end up defeating your coating assembly. Also, I've never needed to use vacuum to remove air bubbles. It may be possible that your recipe/technique introduces more air into the emulsion than necessary. You know my theory of emulsion making: do whatever works for you! (but, thought I'd mention that air bubbles aren't a given).

[Pere Casals]

Thank you for the tip.

I'm in deep debt for the thounsands of tips I found in TLF !!

With an small amount of water under the plates the emulsion goes under, but I found Zero emulsion under plate if excess water and pressing hard. Then it happens some water can go over the top of the plate, and it has to be dried without introducing dust from the cloth, this is the bad side I found, but at least no emulsion was under.

Also detaching the plates was a bit harder...

In the emulsion making I'm still a plain rooky... I'm just obtaining first operative batches...

In fact I was first considering/using the vaccum as a way to remove oxygen from emulsion, this is a well known hypering technique to favor emulsion performance. The idea was later filling the emulsion container with forming gas. But I suspect this has a complexity that is beyond my knowledge, as air can come back in the drying time, so drying should be performed in N2 ambient, perhaps replacing N2 in the drying cabinet some 3 times.

Then I found than degassing eliminated micro-bubbles that could be seen when enlarged, I suspected that as emulsion was desaturated of air then it absorbed well those micro-bubbles, of course if those bubbles are not present then degassing is not necessary.

Also I'm understanding that ultimate perfectionism is not that important , just crafting sound photographs from raw materials it is amazing.

[Robert Brazile]

Interesting stuff, Pere, thanks for sharing it. Recently I poured two 11x14 plates waiter-style, and one went well while the other one...didn't. While I'm fairly certain I can improve my skill at doing so, I think a coating table of some kind is in my future...

Robert

[jnantz]

fantastic !!
thank you for posting this ...
it looks like it makes it eezpeez

[Pere Casals]

Interesting stuff, Pere, thanks for sharing it. Recently I poured two 11x14 plates waiter-style, and one went well while the other one...didn't. While I'm fairly certain I can improve my skill at doing so, I think a coating table of some kind is in my future...

Robert

Hello Robert,

waiter-style is a funny 11x14 term... it made me smile...

Pouring plates with a good "waiter-style" is also great, I think it adds some pepper&salt to the dish...

Anyway sometimes one may want consistency, and then a well leveled table is important, as TLF states...

Regards

[Pere Casals]

fantastic !!
thank you for posting this ...
it looks like it makes it eezpeez

Hello John, after reading your #2 batch for paper, just a tip, if you plan to use a set of glass rectangles as shown to trim the coating thickness you may spray some 3M ReMount glue over the glass to have paper very flat. Now I'm in the plate "business", but I tested with paper, and it seemed to me that placing paper on (Remount) glue sprayed glass it can work if avoiding bubbles by laying paper carefully from top to bottom. Perhaps, instead glue, it would be better plain water or everclear...

I was thinking in coating paper as an in camera "paper positive", rather than "paper negative", by doing a reversal process. This would be better than with darkroom paper because the emulsion can be made faster and with wider latitude...

I find this way exciting, a unique object is obtained, with potential very high quality (like an slide), the original image made with the photons reflected by the subject, with no postprocess, so everything has to be nailed... this is not new... but if positive paper is also self crafted... a matter of purity

[jnantz]

hi pere

thanks for the info !
i am also working on a reversal situation
and about 2/3 finished with a svg tintype type
developer that will reverse the image
my last batch of emulsion i put a tiny amount of dilute dektol in it, instead of hypo
( i was doing something related to kevin klein's emulsion ) and
the unwashed paper emulsion is excessively fast... to slow it down a little i've
experimented by mixing in some bottled emulsion that is about iso 1 .. its still pretty fast !
i'm thinking of emulsion side against the septum through the back of the paper
in-camera paper negatives ( or paper reversals )... been busy the past 5-6 weeks ... so i have back-burnered it...
have fun with your plates !
john