PDA

View Full Version : Removing emulsion from glass plate



John Jarosz
10-13-2006, 06:08 AM
Hi all,

I have a couple of old glass plates with an unprocessed emulsion on them. I 'd like to use the plates for another project. What's the best way to rmove the original emulsion? If I simply fix the plate is everything rmoved?

Thanks

john

Jerevan
10-13-2006, 07:35 AM
I only have experience with exposed plates, but I think water (or some other liquid) would remove it off from the plate. I'd prefer just to cut a few new glass sheets in the same size (or have someone to do it).

If they have been kept in the dark and are not exposed, they may be of interest to someone here on APUG. There are a few people around who indulge in exposing old glass plates. :)

EDIT: btw, if you decide to cut plates yourself, be aware that the edges are very sharp. Use something to sand them down a bit so you can handle them safely. Glass cuts can be horrible.

raucousimages
10-13-2006, 09:46 AM
Sodium Carbonate in hot water is used to reticulate negs. if you leave it too long the emulsion will just fall off of the film base. Shuld work for plates as well.

Roger Hicks
10-13-2006, 10:12 AM
Hi all,

I have a couple of old glass plates with an unprocessed emulsion on them. I 'd like to use the plates for another project. What's the best way to rmove the original emulsion? If I simply fix the plate is everything rmoved?

Thanks

john

Boiling with caustic soda is traditional. DO NOT use light alloy saucepans! For that matter, ask yourself how much you want to use boiling caustic soda solution...

Cheers,

R. (www.rogerandfrances.com)

Dave Parker
10-13-2006, 10:17 AM
EDIT: btw, if you decide to cut plates yourself, be aware that the edges are very sharp. Use something to sand them down a bit so you can handle them safely. Glass cuts can be horrible.

I can second, third and fourth this statement!!!! be very careful when handling glass plates that don't have finished edges, I have the scars to prove it!

:o

Dave

Photo Engineer
10-13-2006, 10:19 AM
Hot caustic soda will etch glass.

The best is a sulfuric acid / dichromate solution in which you soak the film. Then you wash in hot water and soak in warm detergent solution. Follow this by another wash and then rinse in distilled water and dry.

Use rubber gloves to prevent finger prints.

PE

Roger Hicks
10-13-2006, 10:42 AM
Hot caustic soda will etch glass.


That's interesting. I have to admit that this was taken from old books; I had not tried it. I wonder if they just didn't worry about the etching, as they were contact printing anyway.

Perhaps, too, you could throw more light on something else I have read in old books but never verified. It is that you sometimes get a residual ghost image on (or perhaps more accurately in) the glass even when the gelatine is fully removed. Hard to believe, but I have seen it asserted in more than one old source (sorry, can't remember where).

Cheers,

Roger

John Jarosz
10-13-2006, 10:54 AM
[QUOTE=Photo Engineer;376962]
The best is a sulfuric acid / dichromate solution in which you soak the film. /QUOTE]

Can you elaborate on the acid strength/dichromat concentration?

Thanks

john

donbga
10-13-2006, 11:45 AM
[quote=Photo Engineer;376962]
The best is a sulfuric acid / dichromate solution in which you soak the film. /QUOTE]

Can you elaborate on the acid strength/dichromat concentration?

Thanks

john
A concentrated solution of lye or sodium hydroxide (about 10%) will do the trick. No need to mess with sulfuric or dichromate. It may take a bit of soaking. But unless there is something special about the glass I would toss it and start fresh - a more effiient use of your time and money.

John Jarosz
10-13-2006, 12:14 PM
It's a long story.

I broke the groundglass element of my Hasselblad "Groundglasss focusing adapter". Don't ask how. The fresnel is fine. I cannot find a source of glass .065" thick. The groundglass is NLA from Hasselblad.

The 2 4x5 glass plates I have are .058 (approx) thick. So the expediant solution seems to be to use the glass to have it ground and sized to fit. I can make some shims to make up the thickness difference.

Thanks for the ideas.

John

Photo Engineer
10-13-2006, 12:49 PM
[quote=John Jarosz;376974]
A concentrated solution of lye or sodium hydroxide (about 10%) will do the trick. No need to mess with sulfuric or dichromate. It may take a bit of soaking. But unless there is something special about the glass I would toss it and start fresh - a more effiient use of your time and money.

I use standard tray cleaning dichromate/acid solution that I make up from an old formula. If you are doing a one-time quick cleaning, then lye is acceptable, but don't leave it in the solution overly long.

Some glasses are not subject to this, for example the good labware glass we use is immune to this for the most part (pyrex), but window glass is very prone to the problem. I use a glass bottle for my 5% sodium hydroxide solution and the glass is quite milky on this cheaper glass dropper.

As for images remaining behind, I never heard of it, but I guess it is possible if sliver metal gets depositied on the glass somehow. Maybe that is why old-timers use the acid dichromate method, as it removes silver deposits that the alkali will not deal with.

If you need ground glass for your camera though, Dave Parker from Satinsnow will custom make you one for a very reasonable price.

PE

John Jarosz
10-13-2006, 01:17 PM
[QUOTE=donbga;377008]
If you need ground glass for your camera though, Dave Parker from Satinsnow will custom make you one for a very reasonable price.
PE

I tried SS but Dave says he cannot get acceptable glass this thin.

John

Jerevan
10-13-2006, 01:24 PM
I am raised with using millimeters, so I had to convert 0.065" so get an idea of how thick that was (1.651 mm). So, armed with my micrometer I went out to the bench and had a look. The leftover groundglass is 2.35 mm, but the glass I had from some abandoned picture frame is 1.85 mm (0.072 inch), so I don't think you should give up just yet on finding some glass.

BTW, I am not really into Hasselblad stuff, but am I right in that is two parts - one plastic fresnel and one ground glass part? For what model? Maybe I can source it over here.

John Jarosz
10-13-2006, 01:52 PM
BTW, I am not really into Hasselblad stuff, but am I right in that is two parts - one plastic fresnel and one ground glass part? For what model? Maybe I can source it over here.

You are correct, there are two parts: a typical groundglass and a fresnel.

It is called "Focusing Screen Adapter" Cat # 41025. Designed for the SWC, but it will fit on the rear of any Hasselblad.

Regards,

john

Jerevan
10-13-2006, 02:01 PM
There is one at B&H for $69, with that part number.

John Jarosz
10-13-2006, 02:24 PM
Actually not a bad price. That may be the cheapest solution. Thanks

john

Dave Parker
10-13-2006, 03:15 PM
The thinnest glass I can get that is acceptable for grinding is 1.94mm thick, most picture frame glass actually is not flat and has waves in it, using picture frame glass, unless the high dollar museum glass is not normally acceptable in this type of application, believe me, if it is glass, we have looked at it and tried to see how it would turn out...that is why I have the glass made for my application, but if I were to do a run of glass for one project like this, the cost factor would be hugh and not economically feasable, it sounds like the B&H route might be your best bet.

Dave