coating plates … how to

i haven’t’ coated plates with hand made emulsion yet, that will happen soon enough …

but i have been coating plates on and off since the mid 1980s …

there are a few different ways to do this, some are easier than others

the first steps are all the same.

you have to wash the plate to make it chemically clean.  you can see if your glass sheet if clean by running water on it
if the water doesn’t “hang”  you are probably OK …  i wash my plates with a scrub brush ( plastic ) and washing soda.  i have a wood drying rack that i put them on so they drip dry.  i also just have them lean against the wall of the darkroom sink.

once they are dry you can coat them with a sub / or binding agent.  glass doesn’t really have anything for the emulsion to anchor to so an intermediary layer of something works.  depending on what sort of emulsion you are using you use a different binding agent …
i only use silver gelatin emulsions now, so my subbing layer would be  …  clear unflavored gelatin.  you can get hard bloom photography grade gelatin, its the same stuff used in the emulsion  …  or you can use cheap store bought knox gelatin.  i have only used knox  …  and it really never let me down.

i add a packet to warm water and let it dissolve.  then i pour it on the plate and put it someplace flat to set-up.  some folks put hardener in their sub layer, i have never done that.

anther binding agent could be clear poly urethane.  i have never used it  ( min wax ) but some do and they have had successes …  others suggest that it might yellow over time.  i’ve never used that so i really can’t comment.

i do know what DOESN’T work …

albumen doesn’t work
collodion ( either photographer’s collodion or pharmacy “flexible” ) doesn’t work
rubber cement doesn’t work either

as i write this, i realize i only used the albumen and collodion when they were not fully dry.
i have never tried to use them when they were dry, and knowing that there are collodion+gelatin emulsions that exist
i haven’t heard of a albumen gelatin emulsion though …

so i guess the jury’s out still on albumen and collodion …

once there is a sub layer there are a few different ways to coat the plate.
FIRST  …  you have to warm your emulsion and turn it into liquid.  i used to heat up a whole bottle and pour it off
but since then i have learned to squeeze out some emulsion into a warming container and have a small amount liquify.  heating and jelling
emulsion ( from what i understand ) can lead to a fogged emulsion.  once you have it in liquid form  …

one way is by total submersion into a tray of emulsion.  i haven’t done this, but from what i understand you can put some sort of covering on the back of the plate ( tape or something similar )  and dunk the plate in the emulsion, pour off the excess from a corner and put the plate someplace flat to even-out and set up.

another way is using a paint brush.  i like using japanese brushes to coat paper but they tend to leave brush strokes.  brush strokes on glass plates can be nice if enlarged on or shot through a camera, depending on the look you want …  i also like using cheap foam brushes.

this next way i was never able to do until this year, i always had trouble down the line and it never worked, but i have been reformed.

folks who write on http://www.thelightfarm.com and http://www.apug.org and mark osterman at the george eastman house have opened my eyes to another, easy and practical way to coat plates.  you need to have a warmish plate so i use a heating pad if my darkroom ambient temperature is coldish  …  and you need a cold level surface.  i use a pizza stone that cold from the freezer.
i have a small glass bottle i pour from, and another container to pour off / drain into.  i hold the plate level, and pour a large puddle of warm liquid emulsion onto it … and i tilt the plate to get all 4 corners ( like one would do if coating a wet plate ) …  and i use my finger to make sure
the whole plate is covered before draining it off into the second container.  after the plate is drained, i put it on the cold pizza stone to set the gelatin.  if the plate needs a second coat i pour on a second coat.  i usually coat maybe 4-10 plates at once, so by the time i am done with the last one, the first one can get its second layer.

i leave the plates flat and level to dry and after a day or so they are ready to expose.

when i process plates i use a coffee based developer and a strong developer.  i pretty much only use ansco 130, and use a 1:2 dilution to kickstart the development, and i put it in the coffee developer to finish.  i don’t rush it, and i agitate the tray  or with a gloved hand agitate the plate by rock it in the developer.  i don’t  use a stop bath but a water bath ( cold ) …  and while i never use hardener for any other process because it tends to be difficult to wash the emulsion and paper free of chemistry, i have a hardener fixer bath.

cold temperatures, an alkaline developer and a hardener in the fixer keep or help keep the emulsion from lifting off the plate.  in years gone by i would get perfect images on the emulsion, but they would lift off the plate, and wash off.  since i started using a cold stone, cold chemistry, alkaline developers and hardener i haven’t had this happen yet…

maybe  …  just a little bit, but not anywhere as badly as it could be.

5×7 and 8×10 glass plates on the horizon !

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