I have many white spots on my plates : help!

[titisteph]

Hello,
I’m a french daguerreotypist, and I practice dag for only 2 years. I work hard to reach the high level of my dreams, but for the moment, I still need some help!
I use the complete process, including bromine and mercury.

This moment, I’m in a worry with a problem I can’t fix :
I always have many white spots on my plates. And I don’t know what it is.
Those spots appears before gilding, so it’s not guilty.

I take really care of my plates : hard polishing, with excellent results (using random orbital sander, ultrasuede and rouge). None dust visible on the plate before iodine (I use a large rubber syringe bulb to remove dust particles).

It appears without using bromine too. So it’s not bromine.

Do you have a solution to fix it?
Thanks a lot!

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[greg7mdp]

Hum, on dirait des particules sur la plaque. Est ce que tu utilise de l’alumine pour polir avant le rouge?

[photolytic]

I can’t answer in French like Gregory but I would be more specific and ask if you use “rottenstone” which is aluminum silicate in your rough polishing before rouge. This can leave small white particles on the plate. The people who make and polish the plates you buy may have used alumina containing polishes. Have you tried cleaning the plates with some dilute nitric acid like they did in the old days?

[titisteph]

Thanks for your help!
No, you’re right, I don’t use rottenstone before rouge… I use to use polish paste wich works very well to remove scratches. I believed it was good enough with only that. I was wrong, I suppose…
So, your advice is to use aluminum silicate, it’s a good idea. I read some topics about that, but I didn’t know it was necessary to use this before rouge.
My plates seem to be perfect after polishing but it seem to be a mistake.

And I don’t use nitric acid… another mistake.

I will follow your good advices and will show you the result!

Thanks!

[photolytic]

I only used aluminum silicate before I bought a high speed rotary jewelers buffing machine.
Now in stead I use that buffing machine @3400RPM with stick rouge-in-wax for the first polish.
After that I clean off the plate using soft tissue soaked with alcohol.
Then I buff with powdered rouge using my random orbital buffer with 18%silk/82%rayon velvet on the sponge pads.
Then I use another ROB pad with powdered lamp black on it.
Finally I used a clean velvet covered ROB pad to remove any lampblack.
Be sure and wipe the backs of the plates to remove and residual polish there.

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[titisteph]

Hello Photolytic,
Thanks for your answer.
I have the same equipment : high speed rotary buffing machine. But I prefer not using it everytime for polishing silver, because it creates small scratches all over the plate. I only use it for copper, and to remove the image of a gilded plate (because the image is very strong and impossible to remove completely with only random orbital sender)

My question is : where do come from those white and black spots? Is it due to some dust included into the silver layer, wich react with iodine?

And is it absolutely necessary to use nitric acid to clean the plate? Because I would be happy not to introduce ANOTHER dangerous liquid into my lab! But if it’s necessary, I’ll do it. But I need to be sure of the efficiency.

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[photolytic]

I use the rotary buffer on every plate but with very light pressure-no scratches.
It is not necessary to use nitric acid-I do not- but I did see it in Daguerre’s manual.
White haze which is almost impossible to remove comes from cyanide plating with not enough brightener.
Platers who specialize in thin silver plating of electrical equipment (1-5 microns),like switches, do not put any brightener in their plating bath to prevent white deposits on more heavily plated objects like 10 -25microns.
This film is extremely difficult to remove unless you buff almost all the silver off.
All platers,like crystofal, who introduced electroplated Dag plates in the 1850’s, used carbon disulfide brightener.
Modern platers sometimes use thiosulfate too.
If your plater is supplying you with dull plate that has been buffed bright after plating may be causing these spots.
With enough brightener the plates should be mirror bright right out the of the plating bath with no buffing.
Is the rubber bulb you used to blow off deposits on your plates clean inside.
An alternate method I used is to buff the plates upside down on a velvet buffing paddle just before iodine fuming.

[titisteph]

Thank you Photolytic!

I don’t know how do you manage to use rotary buffer without doing scratches on the plates. With mine, I always have scratches. The polish is good, but with very small scratches, even with very light pressure. I don’t know where I fail.
So, I prefer using random sander with ultrasuede.

My plates don’t have white haze, fortunately, and they have perfect mirror-like aspect, before buffing. I don’t think the plater who is supplying me use any buffing at all, there is none mark on the plates, except for some little scratches because I think he use a cloth for cleaning them.

So, I think my plater seem to be not bad, and this is a good news. It would we very difficult to find another one here in France.

[photolytic]

The key to preventing scratches when buffing silver on the rotary buffer is to use unstitched flannel buffing wheels.
Have you eliminated the possibility that the white spots are mercury mist from overdeveloping?
Have you tried Becquerel developing on iodine only plates?
Did you still get the white spots on B-Dags?

[CasedImage]

Hi Titisteph

With the white dots – how stable is your mercury pot? – does it move or bounce around when you are operating it? If so you may be causing the mercury to slop around inside. When mercury moves in a container it will throw very small droplets up into the air. If they hit the plate they bond with the silver and cause white spots like this and can be difficult to remove.

www.CasedImage.com

[photolytic]

Mercury splash spots tend spread when the plate is dried and don’t have a black corona like many of those on Titisteph’s plates. Before the plate is fixed some or all of these mercury droplets can be dislodged from the plate surface by holding the plate vertically and by tapping the plate against the inside of the mercury pot.
An accumulation of scum on the mercury surface can cause spots due to a sputtering effect as the mercury evaporates from the surface of the mercury pool at the bottom of the developing chamber. Filtering the mercury will eliminate this scum.

[CasedImage]

Thats interesting about the sputtering, a good reason to filter.

www.CasedImage.com

[titisteph]

Thank you all for your help.
I’m going to answer to all your questions..

I’m sure my spots are not mercury mist from overdeveloping. Spots from overdevelopping are different, and appears only on black areas on plates, not all over.
But I have never tested Becquerel processing.

My mercury pot is extremely stable, it never moves at all during all the processing. And I filter perfectly the mercury before using (very nice surface of the metal, like a mirror). I clean the mercury box before using it.

From the beginning, I have those black or white spots on all my plates, more or less.

Here is a perfect example from another plate. It’s a giant one!

I’m waiting for the aluminium silicate powder. As soon as I receive it, I’ll do a test. Maybe the problem comes from the silver surface.

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[photolytic]

Thank you for the detailed description of your technique. It has been most helpful.
However both Gregory and myself are concerned that our advice about the bad effects of residual aluminum on the surface of Dag plates has some how been interpreted has a recommendation to use aluminum silicate or Rottenstone to remedy the problem. Our advice in fact is quite the opposite, that you should not use aluminum silicate to solve your problem.
You may be correct is surmising that the problem comes from the silver surface however. Maybe something on the surface of the polished copper underneath the silver that affects the surface above. How thick is the silver.
Here is an SEM image and elemental analysis of the surface of Dag plate provided to me by Daguerreotypist Tom Young of Boulder Colorado. The white spots were identified as alumina. The source of the alumina was apparently the supplier of the silvered plates, Theta Plating of Saint Louis Mo. since Tom Young did not polish this plate with alumina.

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[titisteph]

Thank your for your interesting documents!

Ok, I understand… So, I made a translation’s mistake!
I understood that I should use aluminum powder. I was wrong.
So, I mustn’t use it!

The problem seem to come from the way the plate was silvered. Maybe the supplier use alimina powder, I don’t know.

When I send my copper plates to the supplier, they are already polished by myself. And I don’t use alumina. I use chrome oxyde stick with the rotary buffer.

I don’t know if the supplier add more buffing after me, and if he use alumina before silvering.

If it’s true, I’m sad, because I have 12 plates made by this way…

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